neoperl - flow, stop and go


Indicates a reversal of flow direction. Also describes a situation where non-potable water enters a drinking water network.


Refers to the pressure on the down-stream side of the check valve. Can be caused by piping restrictions, gravity or a separate pressure source such as a pump or pressurized tank. Also describes a condition in which the pressure in a non-potable water system is greater than in the potable water system.

Backpressure Stability

All NEOPERL® check valves are built to withstand backpressures commonly specified in national Standards. However, there are some special models designed for higher backpressures, for example in thermostatic mixers.

Back siphonage

Refers to a form of backflow due to a reduction in system pressure causing a temporary sub-atmospheric pressure in a part of the water system.

Clear Water

Refers to water, which may or may not be potable, that is filtered to remove large debris particles.

Cracking Pressure/Opening Pressure

Refers to the minimum pressure differential needed between the inlet and outlet of the valve to lift the plunger off its seat and generate a flow. NEOPERL® check valves usually have a cracking pressure according to the European National Standards. However, other cracking pressure points can be specified on demand.

Crossover Flow

A condition in a plumbing system (for instance a mixing valve) whereby cold water flows into the hot water system (or vice versa) due to a differential of pressure. Check valves installed on both the cold and hot water lines can eliminate the risk of cross-over flow.

Cross Connection

Any connection, permanent or temporary, between a potable water supply and any plumbing fixture or system through which it may be possible for non-potable water to enter the drinking water system.
Example: A washing machine connected to a rainwater cistern and the drinking water supply can create a temporary cross-connection.

Headloss/Pressure Loss/Pressure Differential

Refers to the pressure drop through the valve due to flow restrictions. Usually represented in a curve: Head-loss versus Flow Rate.