Safety Valve For The Boiler (Water Heater): Construction, Installation

Home installation of the boiler is considered a demanding activity requiring maximum compliance with the rules and regulations for connection. In the strapping of the water heater a safety group is necessarily involved, which includes a safety valve for the boiler - a small but functionally important device.

In this article we will consider the varieties of safety fittings, their design features.

We will also give instructions on boiler strapping and advice on the installation of the safety valve, we will give useful recommendations on the choice of a suitable device.

The contents of the article:

  • Stypes of safety valves
  • The construction and operation of the device
    • The design of the safety valves
    • The working principle of the device
    • Why is the installation of the safety valve not enough?
  • Hints for choosing the model of safety valve
  • Hot water heater installation instructions
  • Professional recommendations for installation
  • Conclusions and useful video on the topic

Safety valve types

Failure valves are often confused with non return valves and sometimes simply referred to as \"reverse\". In fact they are two totally different devices, though they have common features.

The check valve is responsible for ensuring the flow of the medium inside the pipe only in one direction, while the purpose of the safety valve is to protect the pipe and the units connected to it against destruction caused by a higher pressure in the network than the norm.

The substitution is made because the second important function of the safety valve is to create a barrier that prevents the liquid from flowing in the opposite direction.

Safety valve for the boiler (water heater): construction, installation

The mechanisms of the industrial type differ from the simpler and more compact devices used in the household. This is what a spring loaded valve looks like on an industrial pipe

There are several types of locking mechanisms to protect complex technical devices against pressure surges. Among them are spring, magnetic-spring, lever-operated, lever-loaded devices.

The choice of one or another type is explained by the purpose of the pipeline and the characteristics of the medium that moves through it: water, oil, hot steam, chemical aggressive solutions.

For installation of an electric boiler, one type of valves is designed - spring ones. They may differ in appearance, but their internal filling looks the same.

Design and operation of the device

Let's start by taking a detailed look at the design and operation of the safety valve.

The construction of the safety valve

The safety valve, like the other types of valves, has a simple construction and is a combination of two spring mechanisms contained in a common metal casing.

There is no fundamental difference between brass and steel products, but brass is slightly more expensive and, according to complaints, serves longer. The springs inside the body are made of chrome steel.

Safety valve for the boiler (water heater): construction, installation

A schematic showing the internal contents of the valve is clearly visible. A part is cut into the pipe preventing the reverse flow of water and perpendicularly a safety module with movable spout

How the device works

The two cylinders perpendicularly arranged have a similar construction but a different function. The part facing the water has a spring and a \"plate\" with O-ring inside.

The spring keeps the mechanism closed and prevents the liquid from returning to the pipe. The ends of the cylinder are equipped with a male/female thread for tapping into the DHW system and connecting to the boiler connection.

The second cylinder has a stronger spring inside that is in neutral state even if the pressure is slightly higher.

If there is a sudden increase in pressure in the line above normal, the spring is triggered and opens the opening for liquid ejection. The outer end of the cylinder is covered by a plug, a screw or a lever device.

Safety valve for the boiler (water heater): construction, installation

Appearance of safety valve with plastic lever: 2 - thread for connection to water mains, 3 - thread for connection to boiler, 8 - mini pipe for liquid outlet, 9 - lever for forced opening

The area marked with a yellow marking in the picture is indicated. It indicates the limit pressure rating at which the valve is actuated. The pressure is indicated in MPa, but this can easily be converted to atmospheres: 0.7 MPa = 7 atm.

Also on the body is an arrow indicating the direction in which the water flows from the DHW system to the heating tank.

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The installed safety valve with pipe

The safety valve body in metal

Metal spring with gasket

Small \"tear-off\" opening for water outlet

Although the hole in the valve allows the water to drain comfortably, Experts recommend not using the manual operation too often.

Use the forced release lever as infrequently as possible and for maintenance or repair purposes you can drain the water by another method, e.g. by unscrewing the water connections.

Why is the installation of the non-return valve not enough?

The safety device is a component part, therefore it is not necessary to look in stores and select a part to install a new water heater. But when transferring the part may be lost.

This is probably why some craftsmen installing used boilers cut in a typical check valve instead of the safety model, which is strictly forbidden by the manual.

Safety valve for the boiler (water heater): construction, installation

This strapping is not correct. There is a horizontal drain with a stop valve and below this there is a non-return valve without a safety mechanism

Any one who starts to operate a boiler with the wrong piping risks not only the equipment but also human life. The balanced thermodynamic action of heating water can get out of control, and then an ordinary water heater becomes a real explosive device.

Pressure increased to 5-6 atmospheres raises the water temperature inside the tank to the critical boiling point and then even higher. A huge amount of steam builds up and an explosion occurs.

Safety valve for the boiler (water heater): construction, installation

The consequences of an explosion of a domestic water heater in a city apartment. The result of wrong water heater strapping is broken doors and destroyed walls not only for the equipment owners but also for the neighbours

When using a standard safety valve for a domestic water heater everything is different: when the pressure reaches a critical level the spring in the device is compressed and releases a part of the liquid outside.

Thanks to that the pressure inside the system is balanced and the equipment continues heating in the normal mode. For this reason the installation of a safety device is compulsory and regulated by the installation requirements.

The safety device thus performs a number of functions important for the normal operation of the boiler.

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Protection against water hammer and critical pressure

Return valve

Feed-in safety device water from the boiler

Compliance with the technical operating rules

The manufacturers of the boilers strongly recommend the professional installation of the water heaters. If this is not possible, all installation activities must be carried out strictly according to the instructions, respecting all standards and making sure the safety module is installed.

Tips for choosing a valve model

As already mentioned above, water heaters come on sale with a safety valve. That is why there is no need to worry about the correct choice when purchasing a new model especially a brand new one.

The purchase is required in three cases:

  • You have a second hand boiler without safety valve elements;
  • the safety valve was lost when moving;
  • the valve is broken or worn out.

You will easily find a new element knowing the boiler model. The pressure limit values can be found in the instruction manual - these must also be stamped on the body of the new part.

Safety valve for the boiler (water heater): construction, installation

A valve with a lower pressure limit value or, conversely, a product with a reserve should not be purchased. In the first case you will see a constant leakage from the tank, in the second case the valve simply will not work in case of an emergency

The thread diameter must match the dimensions of the mounting connector and the DHW piping. In addition to the device itself, a linen thread on the pipe or a rubber gasket is required if a flexible pipe is used.

Sometimes a valve is installed between the boiler connection and the fuse to drain the water. This is a permissible, permissible piping scheme, but on one condition - the valve must be mounted on a horizontal branch from the water supply line. There must not be any shut-off devices between the safety valve and the water heater.

Heater piping installation instructions

Installation of the safety valve is one of the steps of the boiler piping. The minimum set of parts for the installation of a HTW line is a polypropylene pipe and a safety valve

But we will consider another version, in which, besides the above-mentioned elements, a T-piece, a drain cock and an American pipe are involved. In addition PP fittings will be needed in order to offset the water pipes to the wall.

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The first part is a ½\" brass tee necessary to fix the shut off valve. It is connected with packing material and special paste, tightening 3-4 turns

The shutoff valve is necessary to arrange for additional water drainage for repair and maintenance work. It cannot be installed without a tee

The metal valve is taken from the starter kit, as the boiler is new. It is necessary to carefully inspect it from all sides, check the presence of springs and the working order of the lever

An arrow is stamped on one side of the body surface, showing the direction in which the water should move. The device should be fixed to the pipe so that the arrow looks up and the hole for drainage - down

Tighten the valve by screwing, using the same packing and assembly paste. If there will be an emergency release of excess water from the tank, it will flow from the hole directed downward

Directly to the safety valve screwed \"American\" - stop valve. For fixation, a union nut with a rubber insert is used. On the second pipe boiler also set the \"American\"261>

Adapters are needed to take the water lines closer to the wall. If they do not interfere, then the polypropylene pipes attached directly to the lower valve - \"American pipe\"

Polypropylene, often polypropylene, pipes are connected by welding and through fittings. It remains to connect the discharge pipe to the fuse

Step 1 - Installation of the T-piece for the discharge cock

Step 2 - Installation of the shut-off valve on the tap

Step 3 - Selection or preparation of the safety valve

Step 4 - correct location of the fuse on the pipe

Step 5 - Installation of safety valve on the tee

Step 6 - Installation of the \"American pipe\" to connect the pipe

Step 7 - Installation of the polypropylene adapters

Step 8 - Connection to the tap water system

The complicated safety node is not always used. Some installers think that one safety valve is enough. This is the minimum option for boiler piping.

If tees or other adapters are not used, the safety valve is fixed directly on the spigot of the boiler. It may be hidden behind the casing or may be 1-2 cm lower, which is more convenient for the connection.

Safety valve for the boiler (water heater): construction, installation

An installation option when the safety device is threaded directly on the boiler connection. Both elements have ½\" threads. For the sealing, a packet is used, which is considered specifically for such connections better than fum-tape

It remains to provide a drain for water through the hole in the fuse. A flexible plastic tube of suitable diameter is used for this purpose. It can be white, colored or transparent.

The tube is put on the minipipe of the valve with one end, with the other end in a sewer tee or directly into a drain. Consider the possible installation options.

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Plastic drain tube

Drainage of water from the hole

Installation of tube and shut-off valve

An option to connect the pipe to the sewer

Homeowners who are inconsiderate drop the drain pipe into a bucket or jar is wrong. If a container will save you, it will only save you from being constantly swamped.

In an emergency, the volume of water moving through the tube increases, and the container may simply not be enough. The only correct solution is to divert the drain into the sewer pipe by inserting a tee or separate inlet.

Professional installation guidelines

Even a procedure as simple as installing a shut-off valve relies on following some rules. For example, room design often requires masking the piping and safety group.

Hiding the devices is possible but with three conditions:

  • The length of the flexible hose or pipe from the fuse to the tank must not exceed 2 m, otherwise excessive additional pressure on the valve spring will occur;
  • ideal installation of the fuse is directly to the boiler connection and if this does not work, a tee installation is still excluded;
  • a maintenance hatch must be provided for the valve.

Many people worry when they see water droplets on the valve spigot. This is a normal phenomenon, indicating that the device is functioning.

Small pressure surges in the main line occur from time to time, which provoke a minimal discharge of liquid. You should be alarmed when water either does not appear at all or pours continuously.

Safety valve for the boiler (water heater): construction, installation

The line distance between the water heater and the fuse should be minimal. This is not for aesthetic reasons, but so as not to create additional pressure in the pipes

It should be remembered that self-modification of the safety devices is strictly forbidden. If you need a valve for 0.8 MPa, it is necessary to buy a new product, and not try to somehow remake or adjust the device at 0.7 MPa.

If in doubt about the performance of the safety valve, you should remove it and check whether the spring or seal is not clogged. Is there a problem with the water heater itself and you do not know what to do? We recommend reading about frequent boiler breakdowns and repairs. You lack the skills - call in a service technician.

Conclusions and a helpful video on the subject

To ensure that the installation process of shut-off and safety fittings runs smoothly, without mistakes or misunderstandings, before installing the valve and other devices, read the experience of experienced boiler owners.

About design and operation again:

A few things to take note of:

As with any fitting for piping, the safety valve is an essential device for proper operation of the water heater. It should not be confused with a non-return valve and should only be installed according to instructions.

If you have difficulty selecting or installing, contact an experienced professional who will have your boiler up and running within half an hour.

Want to understand the purpose of the safety valve and the finer points of installation? Maybe you still have questions after reading our article? Don't hesitate to ask our experts for advice in the comments block.

If you are an expert in boiler installation, maintenance and repair, and you have noticed an inaccuracy in our material or would like to add practical recommendations to what we have said, please write your opinion under this article.

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