Backflow
Indicates a reversal of flow direction. Also describes a situation where non-potable water enters a drinking water network.
Backpressure
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 mod-els 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 tempo-rary, 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 connec-ted to a rainwater cistern and the drinking water supply can create a tem-porary 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.