Check valve in the central heating system

Check Valve - What Is It and What Is It For?

It is a very small device, usually installed in heating systems where water flows - such as in home heating installations. Its task is to influence the circulation or, simply put, the flow of water in the installation in such a way that it always flows in one desired direction and does not reverse. Theoretically, circulation pumps for heating systems provide such flow direction, but in some cases, it is worth additionally securing this issue by installing a check valve. Reversing water can be dangerous for our installation. By having a check valve in the right place in the installation, we are sure that the water will not reverse.

How Does It Work? How Does a Check Valve Function?

As shown in the attached diagram - thanks to the design of the valve, it is able to open under the pressure of the liquid to initiate flow in the expected direction, but at the same time block the opening of the valve in the opposite direction. The diagram is very simplified, as there are check valves of different designs and constructions. However, the principle of operation is generally the same and is based on the use of simple laws of physics, pressure mechanisms.

Does It Have Any Function Besides Blocking Water Flow in the Reverse Direction? Is That the Only Function of a Check Valve in a Heating Installation?

This is the most important function, but the function of the valve does not end there. In reality, in many installations without a check valve, circulation pumps are exposed to faster wear and tear - so such a valve should be considered a device that has a positive impact on other elements of the installation and their longevity. It is not said that a heating pump should not work without a check valve, but it is presumed that in an installation with a check valve, it should have a longer lifespan, as it is less prone to failure (because it does not have to work against the back pressure of the reversing medium). We all can imagine what a failure of the circulation pump in winter means.

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Does a Check Valve Require Maintenance or Servicing, Inspection, etc.?

Naturally, it is a maintenance-free device, which we forget about after installation. We can imagine a situation where many of its user-laymen, who have it in their installation, are unaware of this, as they entrusted the installation from A to Z to a professional contractor. If we have no problems with the installation - we don't really need to be interested in the check valve.

Where Is a Check Valve Installed?

Our information in this regard is of an orientational and general nature, we discuss frequently occurring cases. It is worth remembering that the placement of the check valve in the installation should be a decision of a specialist who has seen and knows the given installation.

An important issue may be the protection of devices that are components of the heating installation. For example, it is recommended to install it near pressure tanks if we have water from our own well. In this case, a valve mounted between the pressure tank and the circulation pump will protect the pressure tank from any backlash, which can be very beneficial for its technical efficiency. Additionally, a check valve in such a location can play a positive role in moments of pump failure (or lack of power to the pump, if we do not have backup batteries to support its operation). A warm system is able to largely work gravitationally, but in this case, the check valve will significantly support this work. So we can count on the fact that in the event of a failure - the heating will largely continue to work gravitationally, maintaining the temperature in the house.

The check valve is also often present as a component of pump groups, very often on the cold side. Its task is to assist in the circulation of water before returning to the boiler, to avoid water stagnation in the boiler and overheating of the system. In the following photos, although not visible, it is located under the blue thermometer, just before the manually operated shut-off valve.