Valve for a water heater: which one is needed and why

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). This is how serious matters are. And its correct piping is a safety valve for a 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 standard. What causes the 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 the water leads to an increase in pressure. It may well happen that it exceeds the ultimate strength of the device. Then the tank will explode. To prevent this from happening, they put a safety valve for the water heater.

It looks like the installed valve to relieve pressure in 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 system, 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. There are often situations when water barely runs out of the tap. Then hot water from the boiler will be forced out into the water supply system by pressure. In this case, 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 more terrible if they get hot, and at this time the pressure in the water supply rises sharply. The water that gets on the hot heaters evaporates, there is a sharp increase in pressure - in a jerk - which leads to a guaranteed rupture of the boiler flask. At the same time, a decent amount of scalding water and steam, under high pressure, breaks out into the room. What this could threaten is understandable.

How does it work

A safety valve for a water heater would be more correctly called 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 "T" (see photo). In the lower part of the body there is a check valve that prevents the outflow of water from the water heater when the pressure in the system drops. In the perpendicular branch there is another valve, which, when pressure is exceeded, allows part of the water to be released through the fitting.

Boiler safety valve device

The mechanism of work is as follows:

• While the pressure in the boiler is less than that in the water supply (when filling or when the tap is open), the disc-shaped plate of the check valve is pressed out by the stream of water. Once the pressure is equalized, the spring presses the plate against the body lugs, shutting off the water flow.
• When the heating is on, the water temperature gradually rises, and with it the pressure rises. 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 discharged through the fitting. When the pressure drops to normal, the spring locks the passage, the water stops flowing.

By the principle of operation, it is clear that water from the nozzle will constantly undermine. 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 merging liquid must be removed.To do this, a tube of a suitable diameter is put on the branch pipe, it must be fixed with a clamp. The normal working pressure of the boiler is between 6 bar and 10 bar. Without mechanical fastening, the tube will rip off in no time, so we select a high-quality clamp, tighten it well. Take the tube into the nearest sewer.

One more point: the pipe for the fitting needs to be transparent and preferably reinforced (the so-called "herringbone"). Why reinforced is understandable - because of pressure, and transparent - for the ability to control the device's performance.

Types and varieties

If we are talking about ordinary 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.

Boiler safety valve with forced pressure relief

Pictured above are two safety valves with release levers. They are needed for periodic performance checks. The lever flag is raised up. He pulls the spring behind him, freeing it to discharge water. This check should be done about once a month. You can also empty the boiler tank - raise the flag and wait for everything to drain.

Design features

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

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

Safety valves - serviceable and not

Also pay attention to the shape of the water outlet. The model on the left has a long, non-linear choke. The hose will fit quite easily on it and the length will be enough to install the 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 the hose on it, but the clamp is questionable. Unless crimp with wire ...

The next photo shows 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 clogging, scale and other dirt.

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

For large boilers

All of the above models are suitable for water heaters up to 50-60 liters. Other models are available for larger boilers, many of which have additional devices built in. This is usually a ball valve and / or a pressure gauge to control pressure.

For boilers up to 200 liters

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

With pressure gauge and original

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

Can I install other valves

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

Another case is the installation of a check valve only. It will not let the water drain when the pressure in the water supply drops, but it will not save you from increasing the pressure in the boiler. So this option is also not workable.

How to choose and install

Select a safety valve for the water heater according to the pressure for which the unit is designed. This figure is in the passport. The volume of the tank also affects the choice. 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: linseed tow or fum tape is wound on the thread, after which the valve is screwed onto the branch pipe. It is twisted all the way by hand, then one or two more turns with the keys. It is much more important to choose the right place for its installation. When installation of a water heater this valve is installed directly on the cold water inlet.

Installation example

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

Boiler safety valve installation diagram

The diagram has a ball valve. It is necessary to empty the tank before storage 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.

Installing the safety valve after the tee

Actually, these are all normal options.

Breakdowns, causes, elimination

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

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

Boiler piping with safety valve and reducer

How to check if the valve is working properly? If there is an emergency reset lever, this is easy to do. When the boiler is turned 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 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.

It looks like a reducer - to stabilize the pressure on the boiler

Constantly dripping water is unpleasant and “hits” the wallet, but not dangerous. It is much worse if, when heating the water, you never have water in the pipe. The reason - the valve is clogged or the outlet fitting is clogged. Check both options. It didn't help - change the valve.