Check valve for water heater

Constant presence of hot water in the house or apartment - for the majority of people it is already for a long time has become the usual norm, without which it is difficult to imagine a normal, comfortable life. If there is a water supply to the housing or an autonomous uninterrupted water supply is organized, for example, from a well or a well, the has nothing to think about - you need to install a water heater of one type or another.

Probably the leading position of in is the one among water heaters for domestic use are electric boilers. They are extremely simple to operate, their installation does not require any additional reconcile procedures or individual project drafts. Installation of such a boiler is quite feasible and for self-conduct. That is why information is needed that will be outlined in this publication - each of the home masters should clearly understand how important a safety check valve is for a water heater.

would not have been warned by workers of housing and communal services, emergency and rescue services, supervisory bodies of the state inspection, which would scenes with consequences of accidents neither showed on television, all is equally scary "clever"which all these technical recommendations and just kind advice - not the edict of , they themselves "know how easier and better".Alas, ignoring the very small, inexpensive, easy-to-install, and at the same time - extremely important object of tying the electric water heater can turn out to be very big trouble, and, it is possible, even a tragedy.

The device and operation principle of the

First of all, you must immediately make a very important reservation. In spite of the fact that very often uses the search query "check valve for a water heater" very often to get information, the is more accurate , it will be more correct to talk about a safety valve that combines several functions. These devices have defined similarity, but there is also a huge difference, which predetermines the main task - providing safety of operating the electric heater.

For comparison - consider a conventional non-return valve:

This is a metal cylinder , on both sides of which there are threaded areas for "packing" in a straight pipe section of the appropriate diameter. The disk valve with a rubber seal around the circle is stopped inside, on the central axis - the rod( display on the on the green arrow).The disk is constantly in a spring-loaded state, blocking the internal channel for the passage of water.

When water flows in the direction of the arrow( the direction of the permissible fluid flow is always indicated on the valve body - in the figure this mark is indicated by the red arrow), the pressure in the pipe compresses the spring through the "plate" and opens the passage. As soon as the pressure decreases, the valve again automatically switches to a closed state.

This precaution is absolutely necessary so that the tank is always filled in the water heater under any circumstances. However, such a measure is clearly not enough to ensure security - this will be described below.

Safety valve is somewhat more complicated:

In fact, these are two valves in one housing, placed perpendicular to each other.

In the larger cylinder( item 1), which goes on the water course, the same valve is installed, which prevents reverse water flow. On the feeding side, the "daddy" threaded section( item 2) for tapping into the water supply system( in particular, it will be convenient to connect the flexible waterway hose).On the opposite side there is a threaded coupling "Mama"( item 3), which in some cases is screwed directly onto the regular branch pipe for cold water supply in the electric heater.

In the figure, the "plate" of the check valve( item 4) with a sealing ring around the circumference is very clearly visible, and the spring( key 5), which keeps the valve closed.

And now - the main difference. Perpendicular to the cylinder with check valve, the is still one, somewhat smaller in size( pos.7).In fact, in the it has the same poppet valve, but the spring is much more powerful - this is the same safety "stall" valve. The usual and even slightly increased pressure in the water supply system will not be able to compress the spring and open it - this requires much more serious effort.

In the cylinder cavity, behind the "relief valve" plate, there must always be a hole with a nozzle( key 8), where, when the valve is operated, a surplus of liquid will be discharged.

Cylin with with a safety "break" valve can be completely muffled by , and sometimes it ends with a screw plug( behind the plug) behind which is the adjusting screw( usually - for "internal" hexagon).But the most common safety valves with an additional lever:

The figure clearly shows the features of such a device. The lever( key 9) is intended for manual opening of the safety valve with discharge of water through the pipe( item 8).Note that the nozzle can have a special relief design, which allows you to put on it thin hoses to drain water into the drainage( sewage).The function of manual valve control is convenient, for example, for draining the contents of the boiler during maintenance or maintenance work. However, , "get carried away" using such manual control should not be - it may be in some cases even dangerous( this will be discussed below).

Any safety valve always has an arrow indicating the direction of the cold water flow towards the electric water heater.(on the scheme - the red arrow).Very often on the body the maximum pressure of the "break" valve is indicated - in the this case is 0,7 MPa or 7 atmospheres( yellow circle in the figure).

How the safety valve works in various situations

In order to finally verify the importance of the safety valve, it is best to consider the cases in which the of which the is working, and also the situations which can occur if, for some reason, the valve is missing ordefective.

For clarity, more times - the simplest, but also the most understandable scheme of piping a boiler with a safety valve. The blue and red arrows indicate the direction of the flows, respectively, of cold and hot water. The green arrow points to the mounting position of the safety valve .

1. After the electric water heater has been installed, it is completely "tied up", it should be filled. For this, the cold water supply and the hot tap on one of the mixers are simply opened. The pressure in the water pipe is sufficient to open the check valve for unimpeded flow. As the fills the volume of the water tank, air is removed. As soon as the flows from the mixer - all capacity is filled to the upper intake branch, the supply can be switched off.

Pressure in the boiler in this Mom nt pr is equal to pressure in the cold water main - it seems to be "propped up" by it. However, it can be even slightly higher - for account the remaining compressed small volume air in the upper part of the tank. Plus, when the power is turned on, water heating starts - and this is the , too, , naturally, the drives the to increase the pressure.

2. Imagine the situation that the check valve is not installed , or is in a faulty state. That balance, which was reached when filling tank boiler, sooner or later is broken, as the pressure becomes higher than the pressure in the pipe. The "hot" faucets on the faucets are closed, which means that the heated water will look for an outlet in a different direction. This can lead to the fact that hot water suddenly starts to flow from the "cold" tap, or it is filling it with a drain tank on the toilet. And the meanwhile the boiler thermostat can not understand the situation and not the gives the signal to disconnect the TANS .The expensive electric energy is wasted absolutely in vain.

3. But this is still - not the saddest. It's no secret that pressure in the water main, especially in high-rise buildings, often drops to critical values ​​(from the tap, is hardly flowing ), or even completely disappears. The reasons for this are a great many, for example, an accident on the mainline, preventive maintenance, planned pressure reduction, for example, at night and , .What will occur in the absence or malfunction of the check valve? Yes, nothing good - the boiler just emptied, since all of their water will flow out completely into the feed pipes.

Well, if the boiler is provided with protection against "dry" heating, and it will work quickly! And if not? Powerful TANS will idly heat the air in the closed volume , and this will end either by their burning out or by the cracking of the enamel - in any case, nothing good to expect in this situation is not necessary.

4. A reasonable question may arise: should be limited to only by installing this same check valve? It would seem , judging by the description, it is able to solve all the problems.

No, you can not. The installation of a complex valve, combining both the reverse and safety, is a prerequisite for the safe operation of the water heater.

If somewhere the reader will encounter such a picture - only a check valve at the input, then he should understand that this is comparable to a bomb that is stored, which is unknown when jerks .

We consider the situation in detail. When the boiler starts up, the heating starts and, with the rise of the temperature, according to the laws of thermodynamics, the pressure in volume starts to increase.

The designers of household appliances lay in each water heater a certain service life, which allows the device to operate up to the of certain pressure values ​​in the of the capacity - this is usually indicated in the technical documentation. Usually, all boilers are very balanced thermodynamic systems, in which the optimum ratios of permissible temperatures and pressure levels are very accurately calculated. Nevertheless, , it can be anything. And as soon as the pressure level, for whatever reasons, begins to approach the permissible upper mark, a spring is compressed on the safety valve, and the resulting excess liquid is discharged into the drainage branch. As a result, the system again enters a state of dynamic equilibrium.

And now let's try to imagine what can happen in a situation where there is no emergency valve and everything is limited only to reverse

. The water heating should be limited by the thermostatic regulator, but quite often these electromechanical devices - are far from perfect, and can simply fail. In this case, the heating continues uncontrolled.

The pressure inside the tank grows , but there is no way out - the mixers are closed, and the check valve reliably closes the supply line. It would seem that the temperature will reach only to 100 degrees, to the boiling point of water? Nothing like this! With increasing pressure in the closed volume , the boiling point of the liquid also sharply increases. For example, the data are shown in the table:

Closed-box pressure, atm( MPa)	Boiling point of water, ° Ċ
1.0( 0.1)	99.09
1.033( 0.1)	100.0
1.5( 0.15)	110.79
2.0(	)
6.0( 0.6)	158.08
6.0( 0.6)	158.08
6.0( 0.6)	158.08
6.0( 0.6)	is an
5.0 ​​(0.7)	169.61
9.0( 0.9)	174.53
10.0( 1.0)	179.04
20.0( 2.0)	211.38
25.0( 2.5)	222.90
50.0( 5.0)	262.70
100.0( 10.0)	309.53

When the word "bomb " - is not at all out of exaggeration! In similar circumstances, the water heater turns the really into an explosive device of a terrible of destructive power.

Already at 4 - 5 pressure atmospheres, the boiling point reaches almost 150 ° With , and continues to rise. The growth of pressure on the walls can lead to their deformation, chipping of the enamel or ceramic coating - but this will be the smallest of possible evils. The - drastically decreases the pressure drop in this closed system, and this can happen when a crack appears on the weld, when a rubber seal breaks out or even just when a hot water tap is opened on the mixer.

A sharp decrease in pressure results in the corresponding drastically reducing the boiling point of water. As a result, the entire volume of liquid( imagine all 50, 80 or 100 liters!) Instantly boils, which, of course, is accompanied by the release of a huge amount of steam. This will not withstand any, even the most solid body - should be the strongest explosion, which is capable of demolishing everything on the its path, including even brick interior walls. There are many good examples of this on the Internet.

So, will lead the brief results on the need for a safety valve.

- It does not allow back water leakage from the tank into the pipeline feeder, in case of head loss.

-Valve on on creates additional protection for the boiler against possible strong pressure spikes in the water pipe, from hydraulic shocks.

- The safety valve will eliminate the possible failure of other levels of safety - it will maintain the temperature-baric mode in the boiler within the limits of acceptable values.

- Safety valve, equipped with lever, allows, in addition, to drain water from the boiler if necessary.

Video: the need to install a safety valve

Recommendations for the selection and installation of a safety valve

The choice of the required valve is simple. Most often, boilers( especially from leading manufacturers) go on sale with a valve of the required denomination. At the same value, will need to be oriented, if for some reason will have to change the valve in the future.

The value of the maximum pressure in the tank of the boiler, in addition, must be specified in the product's technical documentation. If the water heater is not equipped with a valve, the will have to purchase the on its own, relying on the value indicated in the passport. It is important to choose the right value - if you install a "weak" valve - water will leak almost continuously from it. The valve with a too strong spring will not create absolutely safe operating conditions.

"Sealed" the valve can directly to the connection of the cold water boiler ( always has the appropriate blue color marking.) For reliable sealing during installation, it is best to use linseed cotton with modern sealing pastes, usually 3 -4 complete revolutions If there is a flexible line from below, then there is enough rubber gasket