Check valve - what is it and what is it needed for?

Check valves, also known as backflow preventers, ensure that water or even gases can only flow in one direction. They open automatically in the direction of flow and close automatically as soon as the direction of flow begins to reverse. Typical applications of non-return areas include mixer taps, gas pipes and radiators.

The valves consist of a disc and a spring. The disc presses against the spring in the direction of flow and thus opens the pipe cross-section. If there is no flow or the flow reverses, the pressure on the spring ceases, so that the pipe cross-section is immediately closed.

Check valves in mixer taps

Mixer tap
Non-return valves are also installed in normal fittings (mixers).

In mixer taps, non-return valves prevent the mixing of cold water and hot water. On the one hand, such mixing is not efficient in terms of energy. On the other hand, lukewarm water provides ideal living conditions for bacteria. In order to shorten the distance between the non-return valve and the tapping point, the valve is always installed just before the fitting. It is usually located in flexible Pex hoses.

Low maintenance intensity can lead to malfunctions

Legionella and other bacteria
Lukewarm, stagnant water provides an ideal breeding ground for bacteria

Today, the mixing of hot and cold water takes place predominantly before the closing mechanism. So there is no physical separation of the hot and cold water lines - even when the fitting is closed. Due to pressure differences between the two pipes, there is a mixing of cold and hot water. As a result, we get only slow-flowing or even stagnant running hot water. Check valves are supposed to prevent this. In practice, however, they are rarely or never maintained. This can lead to limescale residues and other impurities and subsequently to malfunctions.

Closing mechanism in front of the mixing chamber makes backflow valves superfluous.

France is now taking a technically new approach with the French standard NF 077 MM. The standard prescribes the closing mechanism in front of the mixing chamber. The arrangement of the closing mechanism in front of the mixing chamber, which makes backflow preventers superfluous, would indeed be a small step forward for the valve market. Revolution. Because the majority of the current range of electronic or thermostatic fittings does not yet meet this requirement.

Our partner Delabie has a Unique, patented system which ensures that the hot and cold water inlets of thermostatic fittings are closed directly at the connections. Vulnerable backflow preventers can thus be dispensed with completely, and the risk of cold water or hot water flowing back out of the fitting is completely eliminated. More information on how the new cartridges work can be found below.

Copyright: Delabie
Copyright: Delabie