Water pressure in the non-return valve of electric water heaters. Water heater safety valve. Why is there excess pressure?

A safety valve for a water heater, boiler or a check valve device is one of the main elements responsible for the safe operation of the device in conditions of pressure drops when heating water.

Purpose

In the process of heating water in the storage tank of water heating equipment, the volume of liquid increases by about 2-3%. In accordance with the law of thermodynamics, even with a slight increase in temperature, a closed system is characterized by an increase in pressure.

The temperature control devices and thermostats installed in the boilers make it easy and efficient to control temperature regime liquids, but when they fail, the pressure increase inside the system becomes critical.

Safety valve for Ariston water heaters

The result of an avalanche-like increase in the pressure level is a rupture of the boiler body and an explosion of water-heating equipment.

In order to prevent exceeding the permissible pressure limits, a safety valve, capable of dumping part of the liquid out in a critical situation.

However, the functional purpose of the water pressure relief valve for the water heater in water heating equipment is not limited solely to the protection of the boiler, but is also presented:

preventing the return of heated liquid from the storage tank to the plumbing system;
smoothing water pressure surges or the so-called water hammer at the inlet to water heating equipment;
discharge of an excess amount of heated water from the tank in conditions of a critical increase in temperature and pressure levels;
the ability to drain the liquid from the water-heating tank in order to carry out preventive maintenance and repair measures.

The absence of a valve does not prevent the outflow of heated water from the boiler in an emergency, so exposed heating elements burn out in a short time.

The safety valve will prevent backflow of water into the conduit, prevent pressure surges and water hammer, and also allow excess liquid to be drained for maintenance purposes.

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Principle of operation

The safety valve is represented by the main body structure and several elements, which are located in a brass or nickel shell. Usually, this device has an inverted T-shape. A non-return valve is fixed at the bottom of the water heating tank, which prevents water from flowing out under the influence of a drop in the pressure level in the pipeline.

A valve device is located on the perpendicular branch, which operates when the pressure rises, and is also responsible for draining excess fluid through the fitting. A correctly installed device works in stages.

Check valve in the circuit

When the pressure level in the reservoir is lower than that in the pipeline, the filling process causes the poppet plate in the valve to be squeezed out under the influence of water pressure.

The normalization of pressure is accompanied by the closure of the plate and the limitation of the flow of water into the system. The active heating mode is characterized by a slow increase in the temperature of the water and an increase in pressure, which can reach maximum values. In this case, the defense mechanism is activated.

Periodic draining of liquid through the choke channel should not cause concern, as it indicates the functioning of the safety valve of the hot water boiler in normal mode.

Varieties

The safety valve device installed on domestic hot water equipment is most often represented by three main groups:

Protective devices for water heaters with a volume of not more than 50 liters. in the form of disposable valves. A feature is the presence of a non-separable design, low cost and a fairly short service life. However, some very well-known manufacturers of boilers are equipped with valves of higher quality characteristics.
Devices for water heaters with a volume of not more than 200 liters, characterized by a 7 bar safety valve, a check valve and a shut-off ball valve, as well as a special nozzle for connecting to the sewer system.
The safety device for water heating equipment with a volume of more than 200 liters is presented mandatory elements in the form of a pressure reducer, a tap, a non-return and safety valve with a drain fitting.

Completely disassembled safety valves are equipped with special test points that facilitate diagnostics and maintenance of water heating equipment.

Many American manufacturers, as a rule, install closed-type valve devices on their water-heating equipment with no visual control of operation.

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Choice

Most often, all modern water heaters are implemented with an already installed protection system in the form of a safety valve with certain parameters. When purchasing the device yourself, you should pay close attention to the features of the threaded part, as well as the maximum operating pressure.

Installed valve

Each valve is designed for a certain level pressure, which must be indicated in the technical passport of the equipment. The total volume of the tank must also be taken into account. Produced protective systems can have a response threshold from 6 to 10 bar.

If the safety valve is incorrectly selected or installed incorrectly, there may be a constant leakage of liquid or a very strong overheating of the water heating equipment.

Installation

Self-installation of the device, as a rule, does not cause difficulties. Before proceeding with the installation, it is necessary to disconnect the water-heating equipment from the electrical network and drain all the water from the tank, and then carry out the installation, adhering to the following simple recommendations:

the safety element is installed at the cold water inlet to the boiler;
during installation, it is necessary to use a FUM sealing tape or traditional tow;
the second side of the fuse is connected to the cold water supply system;
in the presence of pressure drops in the water supply system, a reducer is installed in front of the valve.

Valve Installation Diagram

A flexible and transparent hose is used to connect the drainage pipe to the sewer system. It should be noted that sometimes a special safety valve is replaced by a demolition device designed to discharge liquid in emergency mode.

Despite the similarity of functions, the principle of operation of such devices is noticeably different, so you should not rely on the correct operation of such a device.

It is forbidden to mount locking devices in the area from the entrance to the water heating equipment to the safety valve, and also to remove the protective element more than two meters from the boiler tank.

Possible breakdowns and causes

There are some of the most common problems that can occur during the operation of the safety safety valve of water heating equipment:

When the boiler is disconnected from the network and the water supply is turned on, liquid flows out of the drain hole. The reason is a breakdown of the safety element or an increased level of pressure in the plumbing system.
When the boiler is connected to the network, there is a minimum water intake, prolonged heating of the water and a constant flow of fluid from the drainage hole. The reason is a malfunction of the safety valve.

All failures associated with a safety valve are usually accompanied by frequent water leakage or a complete lack of fluid flow. In both cases, it is advisable to replace the device with a serviceable protective valve set to similar operating pressures.

It is very important to connect a flexible and transparent hose to the drain outlet of the device, which allows you to easily visually monitor the performance of the safety valve installed on the water heating equipment.

The correct operation of the safety valve installed on the water heating equipment is a guarantee of the safety of property and your own safety, therefore, when choosing and purchasing such a device, you must make sure that it fully complies with the operating parameters and rated power, as well as organize competent installation in the system.

The device of the simplest check valve.

In front of you you see a cylinder cast from metal, with two edges there is a thread for "packing" into a straight section of a pipe of the corresponding caliber.

Next we see the so-called poppet valve. It has the shape of a disk, along the edges of which there is rubber for sealing. The stock is located in the center. Such a valve device allows it to block the internal flow of water.

It is designed to prevent water from flowing back. The principle of operation is the following. If the water runs in one direction, it presses on the spring. The spring is compressed and the valve lets water through. If the water runs in the opposite direction, the spring is not deformed and the valve does not let water through. Since the mechanism is not visible from the outside, in order to know in which direction the water is moving, an arrow is depicted on the valve. Most often it is embossed.

Thus, water will flow into the boiler, and never run back into the water supply system. However, what happens if the pressure is too high? In this case, one check valve alone is not enough.

A boiler or electric water heater has a very fine tuning. If too much water enters it, it will break due to high pressure. Therefore, an additional check valve is needed. Given that this combination is very popular, they were combined into one "safety valve".

His device is as follows. There is a thread on the water inlet. It allows you to wind a water supply pipe or even a hose onto the valve. At the water outlet, which is connected directly to the boiler, there is a threaded coupling. This makes it easier to put the valve on the boiler tube.

Perpendicular to the direction of the water in the valve, below the poppet valve there is a soldered metal cylinder. There is a hole on the side of the cylinder. And inside the cylinder is a “stall” valve. The device of the "stall" valve is the same as that of the check valve. But the spring of the “stall” valve is much stronger, and only allows water to pass when the critical pressure is reached. In this case, the water will exit through the above-mentioned hole on the side of the cylinder.

The hole on the side of the cylinder or nozzle is often embossed so that a hose can be put on it and discharged into the sewer.
From the outer top of the cylinder there may be a soldered plane or a screw plug with an adjustable screw. But most often you can observe a lever in this place. It is available for manual discharge of water through a nozzle.

Often on safety valves they write at what pressure the “stall” valve will open and release “excess” water.

How the boiler and safety valve work

1. After the electric water heater is installed, it can be operated. To do this, you first need to fill the tank with water. The pressure in the water supply system will be enough for the check valve leading to the boiler to let the water through.

Next, air will be forced out of the boiler. Therefore, be prepared that the water will not immediately come out of the mixer. The pressure will be created due to the cold water supporting from the water supply system. As soon as the water has gone, close the mixer and wait. Once the tank is full, the internal pump in the water heater will turn off and the water inside will be heated. By heating the water, steam will be generated, which will create sufficient outlet pressure when the hot water tap is opened on the mixer.

2. Let's imagine that the safety valve is not installed. If pressurized water does not exit through the faucet, it looks for another way. This way is a water supply pipe. It has much less pressure, so hot water starts to go in the opposite direction, and from all taps, while cold water is installed on the mixer, boiling water will pour. The boiler will heat all the water in the pipes, because new water will constantly come. And the internal thermometer will show that the water needs to be heated. And the electricity bill will be exorbitant.

3. It happens that the water disappears. We have to wait for the plumber to come and fix everything. But, while there is no water, it is very dangerous if the valve is faulty. If the valve is defective or missing, all the water will flow out. Well, if the sensor turns off the heating. But this may not happen. Then the air will heat up. This will either burn out the heating element or crack the enamel.

4. A logical question arises: is it possible to install only a check valve?

No, that would be a disaster. If you see such a picture, know that a disaster can happen at any moment.

What can happen?

When the boiler is filled with water and heated, steam is released. The pressure builds up inside. Often, the manufacturer provides for the heating temperature and the corresponding pressure.

If the pressure rises to a critical level, the valve will open and excess water leaks out through the bleeder valve. And the pressure in the boiler equalizes.

If the pressure rises and there is no way out, this promises another problem: with internal pressure, the boiling point of water also rises.

If the pressure continues to rise, the water heater will become a real bomb, and burst from internal pressure. The consequences in this case are devastating.

At 4-5 atmospheres, the boiling point is already 150 degrees Celsius. After that, you can expect the boiler to swell. The walls will bend, causing the enamel or ceramic coating to crack.

But much worse is a sharp decrease in pressure. As mentioned above, pressure reduction and boiling point are closely related to each other. As soon as the pressure will drop, the temperature will remain the same, and it will be more than enough to turn all the water inside the boiler into steam in a matter of seconds. What will cause the explosion.

It can occur from the fact that while the pressure was growing, the seams along which the structure was soldered cracked, and the rubber was torn. A sharp drop in pressure can also occur simply from the fact that you open a hot water tap.

Conclusions about the need for a valve:

1. Water from an electric water heater does not flow back into the pipes if the pressure in the pipes is lower than in the boiler.

2. The valve protects the boiler from water hammer and pressure surges.

3. The safety valve ensures the safety of using the boiler in case other safety systems have not worked. It also maintains the temperature-baric balance.

4. If there is a lever on a specific valve model, you can drain the water, if necessary, manually.

How to choose and install a valve

As a rule, the valve comes with the boiler itself. In this case, if the valve is faulty, you simply go to the store with the faulty model and ask for a new one. If the valve is not completed, you should look in the documentation. The documentation describes what pressure is the limit for the boiler.

It is also impossible to take valves "with a margin". If the valve is designed for less atmospheres than indicated in the documentation, the stall valve will open at operating pressure, and water will flow out constantly. This can also affect your water bills.

If the safety valve shows more atmospheres than the maximum allowable, this valve will not save you from a boiler explosion.

To install, connect the valve to the cold water connection on the boiler. As a rule, the cold water pipe on the boiler is blue.

Use linen tow and sealing paste to seal the joint. If your wiring is bending, a rubber gasket is enough
Alternatively, a drain valve can be inserted between the valve and the water heater. This will greatly facilitate the work with the boiler or just preventive maintenance.

The only thing to watch out for is that:

1. The valve must not interrupt the flow between the boiler and the valve. Shut-off valves is not allowed at this location.

2. The valve must be installed on the branch of the tee.

Installing a check valve for water

Boiler binding. Step by step.

There are two ways to tie a water heater. Both will be presented below. And in both cases it is clearly seen that a safety valve is indispensable.

1. Before choosing a boiler, you need to choose the place that you are willing to give for it. It can be either a wall or floor boiler. Measure the space that you are ready to allocate for the boiler, and with these measurements go to the store.

Please note that when the boiler is installed, it should not interfere with turning around in the bathroom.

Also note that there should be enough space for plumbing. You also need a place for electrical wiring. Very often a separate power cable power supply and a separate machine.

2. Knowing the height of the water heater, you can calculate where the bottom of it will be.

3. There are fasteners on the back of the boiler. Most often it is a bracket. The bracket has two holes on the same level. Hooks are used to attach it to the wall. Sometimes other fastening methods are used. Often, installation instructions are included with the water heater.

4. Making the markup. We measure the distance from the bottom edge of the boiler - to the bar. We transfer the distance to the wall. In this case, we use as a starting point the mark, which was mentioned in the second paragraph.

5. Using a level, draw two horizontal lines at the level of the brackets.

6. You need to measure the distance between the hooks. Often this is 20 cm. But it is better to have some play in order to adjust the position of the boiler later.

7. We transfer the distance between the holes on the bracket to the wall. Namely, on the horizontal lines outlined in paragraph 5. If possible, it is better to avoid joints between tiles for drilling a hole for the hook. Otherwise, a crack may occur during drilling.

8. The following hooks are used for hanging: the outer diameter of the dowel is 14 mm, and the hook in it is 8 mm. The length of the fastener is 8 cm. But often the hooks are included.

9. Holes are drilled in the designated places. Dowel plugs are inserted into the holes. Hooks are twisted into dowels.

10. It is necessary to tighten the hooks to such a depth that the boiler does not ride on them, but not point blank.

11. The boiler is hanging. Below we see two pipes: red - hot water outlet, blue - cold inlet.

12. The master can install an additional tee tap to the branch pipe. It, as mentioned above, will allow the device to be prevented. Before installation, a measurement is made: the number of revolutions is counted before the tee falls into its place.

13. The tee is fixed with tow and Unipac paste.

14. The tee is “packed”.

15. A tow is wound on a perpendicularly located exit, a paste is smeared and a tap is screwed in. For reliability, when twisting, it is necessary to make at least 3 turns. The handle should eventually be available for operation.

16. When installing the safety valve, please note: the arrow on the valve must point in the direction of the boiler during installation.

17. The safety valve is screwed directly to the bottom of the installed tee. In this case, the flow of water is not interrupted, and the rule of absence locking devices between the valve and the boiler is observed.

18. It is desirable that the strapping be collapsible. This will allow you to turn off the device at the right time, and remove it. To do this, ball shut-off valves "American" (sleeve nuts) are on both entrances.

19. We attach a tap with a union nut to the safety valve inlet. In turn, a fitting will adjoin the fitting to put a pipe on it. Also, it will be very easy to disconnect it later.

20. The fitting that is adjacent to the valve may be angled 90 degrees. Thus, the pipe can directly adjoin the wall. Naturally, if you use one fitting at 90 degrees, you need to buy a second one too - so that the pipe is located along the wall.

21. A conventional fitting is installed on the hot water outlet pipe with the transition to polypropylene pipe. This is done for the sake of aesthetics - so that the pipes "bend" at the same level. Therefore, two fittings with an angle of 90 degrees will also be installed below.

22. Welding work is underway. Pipes are brought to the branch pipes, which will divert hot and cold water, spreading it around the house.

23. You can connect the boiler to the outlet, it will heat the water. If possible, a PVC pipe is connected to the branch pipe on the safety valve, the second end of which is lowered into the sewer, toilet bowl, etc., so as not to wet the floor.

Check valve installation. Second option

The second installation option is installation with flexible piping.

1. Sometimes the pipes are hidden in the wall for the sake of aesthetics, and only two pipes are visible from it, to which the boiler must be connected. Ordinary ball shut-off valves are installed on the nozzles.

2. For fastening, the branch pipes are wrapped with linen tow and coated with Unipac paste.

3. The tap itself is put on the pipe by hand, and then tightened with a key. In this case, the lamb should be located on top.

4. At the inlet pipe of the boiler - winding.

5. Installation of a safety valve with a lever. Yes, you can do without the tee, which was considered in the first version. Although at the same time it will take much longer to dry the boiler for prevention. But it's cheaper.

6. The valve is screwed onto the tow and tightened with a wrench. Watch the lever - it should be conveniently located. We won't need more linen tow.

7. Flexible wiring connection. Corrugated hoses made of of stainless steel. Rubber tires are often counterfeited, which causes particles of rubber for tires to be in the water. However, to avoid this, do not be afraid to bend the tube all the way in the store. If it's of good quality, it won't break.

All well-known manufacturers of water heating and heating equipment take their reputation on the market and in the consumer environment very seriously, therefore they do everything to prevent accidents and accidents when using their products. All boilers that heat water under a pressure of more than 1 bar are tested on special stands and installations. But even in this case, manufacturing companies remind in the instructions that it is mandatory to install a safety valve for the boiler. This is the only way to ensure the necessary level of security.

Safety valve, features of the device and installation

From the name alone, you can easily figure out that the main function of the safety valve is to control the pressure inside the boiler. In fact, the design of a standard device includes two valves - a check valve and a safety valve, fig.

To understand how to work with the design, you need to understand the boiler safety valve device:

Both control valve elements are assembled in a T-body made of nickel, iron-aluminum or brass alloy. A non-return valve is installed in the vertical part of the body, a safety valve is installed in the horizontal part;
A red or blue control flag is installed on the fuse rod, with which you can forcefully dump some of the water from the boiler;
The control poppets or petals of both valves must be pressed against the bearing surface or "seat" when in operation;
At both ends, a pipe inch thread, most often its size on the safety valve for the boiler is ½ inch. For a 100-200 liter tank, a ¾ inch boiler safety valve is usually provided.

For your information! Despite the fact that the installation of both valve elements is made in the same housing, they work and break in completely different ways.

As an example of a high quality device, we can recall the safety valve for the gorenje boiler, photo.

The brass body and high pressure casting ensure a long service life even when installed on cheap Chinese boilers. The only drawback is the high price, at least $15 apiece. But given that installing a valve fuse will avoid major troubles, saving on safety does not make sense.

Safety valve actuation

It is worth noting that both valve elements, despite the fact that they are installed in the same housing, operate completely independently of each other. Valve fuse according to the principle of operation is in many respects similar to automatic valve boiler. As soon as the pressure inside the container rises above the limit of 6 bar, the shut-off plate moves under water pressure, compresses the spring and releases the drain hole. Part of the water goes into the sewer until the pressure equalizes to normal.

In addition, a safety valve for a boiler with a descent handle allows you to clean the tank from accumulating salts and sediment. To do this, once every couple of weeks, you need to set the pen or flag to a horizontal position. In some models, you will need to press the flag and hold it for several minutes. Water through the drain washes out particles and sediment that has accumulated in the valve mechanism.

Advice! The safety valve can be used to completely drain the water from the boiler for repair or maintenance.

The non-return valve is designed to prevent the flow of warm water from the boiler back into the inlet water line. As the water in the heating tank is consumed, the locking plate rises under pressure in the line and releases the flow path to fill the boiler.

If the pressure in the water supply drops or rises sharply, the valve disc blocks the flow of hot water back into the line or dampens the water hammer with a spring. The installation of a safety valve for a boiler on cheap Chinese products, in which there are neither thermostats nor thermal electrical relays, is especially relevant.

Without installing a check and safety valve, a Chinese boiler can easily turn into a source of danger - scald the owners with boiling water or flood the apartment hot water. Practitioners often admit that it makes sense to install a safety valve even for an indirect heating boiler, which should not have such problems by default. For example, repair work on water supply systems is almost always accompanied by water hammer and pressure surges, in which case the boiler is subjected to a tough test, regardless of its design.

Features of installation and adjustment of valve devices

Often, when buying and installing a boiler for hot water, the owners ignore the recommendations of the manufacturers and refuse to install a safety device, motivating their decision by the fact that the valve interferes with the operation of the water heater.

Safety valve claims

In fact, the abnormal operation of the valve device may have very specific reasons:

Low quality product;
Abnormally high pressure in the water supply;
Incorrect installation and adjustment of the valve mechanism.

As a rule, high water pressure is typical for the first floors of apartment buildings. With a professional installation, craftsmen are always interested in water pressure. It is impossible to install a boiler and connect it to a water supply system with water at 5-6 bar. Therefore, they try to regulate the pressure using an inlet valve, or they recommend installing a reduction gear, which will immediately solve half of the problems.

The first and third cases are much more difficult and dangerous than high pressure. As a rule, manufacturers of well-known brands of boilers complete their products with very good, high-quality safety valves. When buying, few people check what kind of additional components and materials are attached to the boiler, so branded appliances are replaced during pre-sale preparation with the appropriate size, but cheaper ones. Therefore, when buying or installing, it is worth checking the operation of the device again, so that later you will not be surprised that a safety valve is flowing on the boiler.

The high quality of the valve can be determined by the following features:

The body is made of cast brass alloy, possibly nickel-plated. Cheaper iron-aluminum or copper-aluminum alloys will be lighter, with thinner case walls;
Plastic valve discs, when pressed on the stem, touch the inner walls of the housing or wedge in an extreme state;
The mechanism inside the valve does not provide reliable blocking of the duct even at low pressures. To check, you can press the valve stem with your finger and blow into it. If there is no reliable locking, then it is better to replace the safety valve. Moreover, if the boiler drips from the safety valve, this does not mean that the device is faulty. Most likely, the locking plate is clogged with sediment, but the mechanism itself is in working order and does not require additional adjustment.

If there is no water at all, or the water stream flows in a stream, this indicates that the valve plate is jammed in one of the extreme positions. It will require dismantling, cleaning and adjustment of the device.

But even if the boiler and the safety valve are selected correctly and of the right quality, there is a risk of improper installation and adjustment of the system by craftsmen. For example, it is not uncommon for a hot water safety valve to be hung on a boiler. In order not to find yourself in a similar situation, it is enough to have at least a general idea of how the installation and adjustment of the safety valve is performed.

Scheme of installing the device on the boiler

Requirements for correct installation little valve device:

The safety valve is always installed in the break in the cold water line between shut-off valve and entering the boiler, no other devices should be in this gap;
The maximum distance from the inlet pipe on the boiler to the valve fuse is 180-220 cm;
For most models, a vertical installation of the device is provided, while the water must flow from the bottom up. The direction of movement of the water flow is indicated by an arrow on the body.

The drain fitting on the safety valve must be connected with a transparent PVC pipe to the sewer line. The transparent tube is very convenient to use - you can clearly see how the safety valve works.

Not to drill or cut sewer pipe, you can use a special tee for washing machines, as in the video

Before installation, the body is gently purged with air to avoid a loose fit of the plate to the seat due to debris or scraps of packaging tape that accidentally got inside. The valve is assembled according to the traditional scheme - the thread is wound with a funnel in the direction of tightening the union nut and twisted with an inlet or underwater hoses.

Before starting the boiler, the cold connection is pressure tested under operating pressure. If no drops of water appear at the joints within 5-7 minutes, then the installation is done correctly.

After filling the boiler, it is necessary to check the operation of the safety and non-return valve. The test is carried out "cold". The correctness of the adjustment of the emergency water discharge can be checked with a flag. With a slight pressure, about 1/5 of the full stroke, the first drops should appear, and with full pressure, the water runs in a stream. This means that the factory settings are correct.

Check valve operation can be checked as follows. It is necessary to fill the boiler to the end, then close the shut-off valve at the inlet to the tank and the central inlet. When you open the tap in the bathroom and in the kitchen, water will run out of the pipes for the first couple of minutes. If the flow has not stopped even after 5 minutes, then the “return” does not hold and needs to be adjusted. Indirectly, the departure of water from the boiler can be controlled by the pressure drop on the pressure gauge.

Only collapsible valve models can be directly adjusted. For this, special thin metal washers with a thickness of 0.2-0.3 mm are used. They are placed under sagging springs, and thus the elasticity of the part is empirically selected. Non-separable valves are replaced with new ones.

Conclusion

The service life of a quality safety valve is at least 10 years, subject to regular purging and cleaning of magnesium-calcium deposits. Once every five or six years, the valve must be dismantled and washed from accumulated rust, debris and salts with a special liquid. Particular attention must be paid to the seal on the flag stem. So that the rubber does not rot, once every six months it is necessary to treat the working surface with silicone grease.

Not only the life of the equipment, but also the safety of residents depends on the correct piping of an electric storage-type water heater (boiler). That's how serious things are. And its correct piping is a safety valve for the water heater on the cold water supply.

What is it needed for

Installing a safety valve prevents the pressure inside the device from rising above the norm. What causes pressure to rise? As you know, when heated, water expands, increasing in volume. Since the boiler is a sealed device, there is nowhere for the excess to go - the taps are closed, there is usually a check valve on the supply. Therefore, heating water leads to an increase in pressure. It may well happen that it exceeds the tensile strength of the device. Then the tank explodes. To prevent this from happening, put a safety valve for the water heater.

Maybe you don't need to install a safety valve, but just remove the check valve? With a sufficiently high and stable pressure in the water supply, such a system will work for some time. But the decision is fundamentally wrong, and here's why: the pressure in the water supply is rarely stable. Often there are situations when water barely runs out of the tap. Then the hot water from the boiler is forced out by pressure into the plumbing system. At the same time, the heating elements will be exposed. For some time they will warm the air, and then they will burn out.

But burned out heating elements are not the worst thing. It is much worse if they become hot, and at this time the pressure in the water supply system will rise sharply. The water that has fallen on the hot heaters evaporates, there is a sharp increase in pressure - by a jerk - which leads to a guaranteed rupture of the boiler flask. At the same time, a decent volume of scalding water and steam escapes into the room under high pressure. What it can threaten is understandable.

How does it work

It would be more correct to call a safety valve for a water heater a valve system, since there are two of them in the device.

They are located in a brass or nickel-plated case, which looks like an inverted letter "T" (see photo). At the bottom of the housing there is a check valve that prevents the outflow of water from the water heater when the pressure in the system decreases. In the perpendicular branch there is another valve, which, when the pressure is exceeded, allows some of the water to be released through the fitting.

The mechanism of operation is as follows:

As long as the pressure in the boiler is less than that in the water supply (when filling or when the tap is open), the poppet plate of the non-return valve is pressed out by the flow of water. As soon as the pressure equalizes, the spring presses the plate against the protrusions of the body, blocking the flow of water.
When the heating is on, there is a gradual increase in the temperature of the water, and with it the pressure also increases. Until it exceeds the limit, nothing happens.
When the threshold level is reached, the pressure compresses the safety valve spring, and the outlet to the fitting opens. Some of the water from the boiler is bled through the fitting. When the pressure drops to normal, the spring closes the passage, the water stops draining.

According to the principle of operation, it is clear that water from the fitting will constantly dig in. This happens when the water is heated, when the pressure in the water supply decreases. If you periodically see water on the fitting, then everything is working fine. But the draining liquid must be diverted. To do this, put a tube of suitable diameter on the pipe, be sure to fix it with a clamp. The normal working pressure of the boiler is from 6 bar to 10 bar. Without mechanical fastening, the tube will be torn off in no time, so we select a high-quality clamp, tighten it well. Take the tube to the nearest sewer drain.

One more thing: the tube on the fitting needs a transparent and preferably reinforced (the so-called "herringbone"). Why reinforced is understandable - due to pressure, and transparent - to be able to control the performance of the device.

Species and varieties

If we are talking about conventional safety valves for a water heater, then they look almost the same, only the nuances differ. But it is these small details that are responsible for the convenience and safety of operation.

In the photo above, there are two safety valves with release levers. They are needed for periodic performance checks. The lever flag is lifted up. He pulls the spring behind him, freeing the let to dump water. This check should be done about once a month. You can also empty the boiler tank - raise the flag and wait until everything drains.

Design features

The difference in the presented models is that the model in the photo on the left has a lever fixed with a screw. This eliminates the possibility of accidental opening and complete discharge of water.

Two other differences stand out. This is an arrow on the body, indicating the direction of water movement, and an inscription showing what pressure the device is designed for. Seemed like minor details. But if you can figure out the direction of water movement (look in which direction the poppet valve is deployed), then it’s more difficult with the face value. How to distinguish, for example, at 6 Bar or 10 Bar? Only checks. And how will their sellers be distinguished? No way. By boxes. What if they put it in the wrong box? In general, it is better not to take a valve without marking on the body. These are usually the cheapest of the Chinese designs, but the price difference isn't big enough to make it worth the risk.

Safety valves - serviced and not

Also pay attention to the shape of the water outlet. The model on the left has a long, non-linear fitting. A hose fits on it quite easily and the length is enough to install a clamp. The shape of the fitting on the model on the right is different - with an extension towards the end, but more importantly, the fitting is short. You can still pull a hose on it, but the clamp is in question. Unless you crimp it with wire ...

In the next photo, safety valves without a forced pressure relief flag. The one on the left has a screw cap at the top. This is a serviced model. If necessary, you can unscrew the lid, remove blockage, scale and other contaminants.

The model on the right is the worst of the options. No markings, forced reset or maintenance. These are usually the cheapest available, but this is their only merit.

For large boilers

All the above models are suitable for water heaters up to 50-60 liters. For boilers bigger size there are other models, many of which have built-in additional devices. Usually this is a ball valve and / or a pressure gauge - to control pressure.

The fitting for water discharge here is with a regular thread, so there will be no problems with the reliability of fastening. Such devices already have a rather high price, but their quality and reliability are much higher.

Not for everyone appearance love these devices. For those who give aesthetics great importance very attractive devices are produced. Their price, however, is comparable to the price of an expensive water heater, but it is beautiful.

Can other valves be installed?

Sometimes, instead of a special safety valve for the boiler, they put a subversive one, which is intended for emergency discharge of water for heating. Although their functions are similar, the basic mode of operation is fundamentally different. Demolition should only work in emergency situations. It is designed for salvo discharge of a large volume of liquid. It is not suitable for continuous bleeding of small portions of water. Accordingly, it will not work correctly.

Another case is the installation of only a check valve. It will not allow water to drain when the pressure in the water supply decreases, but it will not save you from increasing pressure in the boiler. So this option doesn't work either.

How to choose and install

The safety valve for the water heater is selected according to the pressure for which the unit is designed. This number is in the passport. Also, the choice is influenced by the volume of the tank. They produce devices with a response limit of 6, 7, 8, 10 Bar. Basically, all units are designed for such pressure. So everything is simple here.

Installation is simple: linen tow or fum tape is wound on the thread, after which the valve is screwed onto the pipe. It is twisted by hand until it stops, then another one or two turns with the help of keys. It is much more important to choose the right place for its installation. This valve is installed directly on the cold water inlet pipe.

Next, there may also be a check valve, which is also called a shut-off valve. But this is already reinsurance - the same device is available in the safety, and often after the water meter at the inlet. The installation diagram is shown below. This is one of the normal options.

The diagram has a ball valve. It is necessary to empty the tank before conservation for the winter (in summer cottages) or before dismantling for maintenance and repair. But more often they put it on a tee, which is screwed directly onto the inlet pipe of the water heater. A safety valve is screwed onto the tee from below, and a ball valve is placed in the side outlet.

Actually, these are all normal options.

Breakdowns, causes, elimination

In principle, the safety valve for a water heater has only two failures: water either often flows from it or does not flow at all.

First of all, it must be said that water bleeding during heating is the norm. This is how the system should work. Water can also be drained when the boiler is turned off, if the pressure in the cold water supply pipes is higher than the valve actuation limit. For example, a 6 bar valve, and 7 bar in the water supply. Until the pressure drops, the water will bleed off. If this situation repeats often, it is necessary to install a reducer, and it is best on the water in an apartment or house, but there are compact models of reducers that can be installed at the entrance to the boiler.

How to check if the valve is working? If there is an emergency reset lever, this is easy to do. With the boiler switched off, it is necessary to raise the lever several times, releasing the excess pressure. After that, the dripping stops and does not resume until heating starts.

If the water continues to drain, the spring may be clogged. If the model is serviceable, the device is disassembled, cleaned, and then put in place. If the model is not collapsible, you just need to buy a new valve and install it.

This is how the gearbox looks like - to stabilize the pressure on the boiler

Constantly dripping water is unpleasant and “hit” the wallet, but not dangerous. It is much worse if, when heating the water, you never have water in the pipe. The reason is that the valve is clogged or the outlet fitting is clogged. Check both options. If it doesn't work, change the valve.

Employees of the Ministry of Emergency Situations, fire protection, housing and communal services, manufacturers of household electric heating equipment do not get tired of warning that the installation of devices must be carried out in strict accordance with the requirements for their safe operation.

Surprisingly, there are people who try to ignore the rules, simplifying the installation scheme, ignoring the installation of a special safety valve.

The explosion of an electric boiler is extremely dangerous, both for people's lives and for the building itself. And the causes of such incidents are most often the absence or malfunction of a small, inexpensive and fairly simple device - a safety valve.

To understand the importance of this safety device, you need to familiarize yourself with its design and principle of operation.

How a safety valve works

The device of the safety valve for the water heater is quite simple. Structurally, these are two cylinders with a common cavity, located perpendicular to each other.

Inside the large cylinder there is a poppet valve, preloaded by a spring, which ensures the free flow of water in one direction. In fact, it is familiar to everyone. The cylinder ends at both ends with a threaded part for connecting the valve to the heater and pipe system.
The second cylinder, placed perpendicularly, is smaller in diameter. It is muffled from the outside, and a drain (drainage) pipe is made on its body. A poppet valve is also placed inside it, but with the opposite direction of actuation.

Often this device is equipped with a handle (lever) that allows you to forcibly open the drainage hole.

How does the valve work

The principle of operation of the safety valve is simple.

The pressure of cold water in the water supply presses the "plate" of the check valve and ensures the filling of the heater tank.

Upon filling the tank, when the pressure inside it exceeds the external one, the valve will close, and as the water is consumed, it will again ensure its timely replenishment.

The spring of the second valve is more powerful, and is designed for increased pressure in the boiler tank, which necessarily increases as the water heats up.

If the pressure exceeds the maximum allowable value, the spring compresses, slightly opening the drainage hole, where excess water drains, thereby equalizing the pressure to normal.

Importance of proper valve operation

Perhaps the description of the device and the principle of operation of the valve did not bring complete clarity to the question of its extreme importance. Let's try to simulate situations where its absence can lead to.

So, let's say there is no valve at the inlet to the heater that blocks the return flow of water supplied to the tank.

Even if the pressure in the plumbing system is stable, the device will not work correctly. Everything is explained simply - according to the laws of thermodynamics, when water is heated in a tank with a constant volume, pressure necessarily increases.

At a certain point, it will exceed the supply pressure, and the heated water will begin to be discharged into the plumbing system.

Hot water can come from cold faucets or go into the toilet bowl.

In this case, the thermostat continues to work properly, and the heating elements consume expensive energy for nothing.

The situation will be even more critical if, for one reason or another, the pressure in the water supply system suddenly drops, which is practiced quite often, for example, when the load at water stations is reduced at night.

Or if the pipes turn out to be empty as a result of an accident or repair work. The contents of the boiler tank are simply drained into the water supply, and the heating elements heat the air, which inevitably leads to their rapid burnout.

It may be objected that the automation should prevent idle operation of the heater. But, firstly, not all models provide such a function, and secondly, the automation may fail.

It would seem that in order to avoid such situations, you can limit yourself to installing ? Some “wise men” do this, not fully realizing that by doing so they are literally “planting a bomb” in their home.

It is scary to imagine what can happen if the thermostat fails.

The water in the tank reaches the boiling point, and since there is no exit from the closed volume, the pressure increases, and when high blood pressure the boiling point of water becomes much higher.

Well, if it ends with cracking of the enamel on the inside of the tank - this will be the least evil.

When the pressure drops (crack formation, open faucet, etc.), the boiling point of water drops again to the normal 100 degrees, but the temperature inside is much higher.

There is an instantaneous boiling of the entire volume of liquid with the formation of a huge amount of steam, and as a result - a powerful explosion.

All this will not happen if a serviceable valve is installed. So, let's summarize its direct purpose:

Do not allow water to flow back from the heater tank into the plumbing system.
Smooth out possible pressure surges in the water supply, including hydraulic shocks.
Discard excess liquid when it is heated, thus keeping the pressure within safe limits.
If the valve is equipped with a lever, it can be used to drain water from the water heater during maintenance.

How to install a valve on a water heater

Choose the right model

As a rule, good boilers come to the consumer equipped with a safety valve of the required parameter.

If not, or if you need a replacement, you will have to buy it yourself. They are inexpensive, 250-400 rubles, depending on the model.

If with threaded part special problems does not occur (almost all valves have a ½ inch thread), then the working pressure of the valve is the value to which special attention is paid.

The required pressure value must be specified in the operating manual of your heater.

If you purchase a valve with a lower pressure rating, it will constantly flow from it. If you choose a value greater than the allowable one, the valve may not save you from big troubles when the boiler overheats.

How to install

Before installing the safety valve for the boiler, the device itself must be turned off and the water drained from it.
The valve is installed at the cold water inlet to the heater. The process is simple - the usual "packing" with a key for 3-4 turns using seals (fum tape or tow, as you like). The second threaded end of the valve is joined to the cold water supply system.
Be sure to check the direction of the incoming water - it is marked with an arrow on the valve body.
If the pressure in the water supply system is not stable, it is excessively increased, it would be better to put a water reducer in front of the valve.
Not everyone likes the fact that water starts to leak from the valve from time to time. This is a completely normal phenomenon, saying that the device copes with its direct task. It would be wise to connect the drain pipe with a flexible hose to the sewer system. The hose must be transparent so that you can visually assess the performance of the valve.

Attempts are sometimes made to hide the valve out of sight by placing it away from the heater. This approach is also possible, but subject to two conditions:

It is strictly forbidden to install locking devices between the valve and the boiler inlet.
A long vertical section of water supply will in itself increase the pressure on the valve, and absolutely unnecessary "idle" leakage may begin. In any case, there should be no more than 2 meters between the valve and the boiler.

What should I do if the water flows out through the drain pipe too abundantly, even without getting very hot?

It is possible that the pressure in the water supply is too high (although this is extremely rare) - in this case, installing a reducer will help.

It should also be checked - it is possible that a valve with a too low pressure indicator was purchased that does not match the heater model. If everything is normal here, it means that the valve spring has “sat down”, and it should be changed.

More concern should be that the valve is always and under all circumstances dry.

If even at maximum heating a drop of water has never been shown from it, with a high degree of probability we can talk about its malfunction, clogging or jamming. It's better not to risk it and buy a new one.

A simple installation of this absolutely inexpensive device will protect the life and health of the owners of the house, and preserve their property, and extend the period of trouble-free operation of the water heater.