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Absolute pressure |
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Definition
The addition of gauge pressure and atmospheric pressure. Usually indicated as psia.
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Term |
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Atmospheric pressure |
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Definition
Pressure exerted by the weight of the atmosphere. Decreases as the elevation above sea level increases (14.7 psi / 407” water column at sea level).
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Term |
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Backflow |
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Definition
Indicates a reversal of flow direction. Also describes a situation where non-potable water enters a drinking water network.
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Term |
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Backpressure |
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Definition
Refers to the pressure on the downstream 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.
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Term |
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Backsiphonage |
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Definition
Refers to a form of backflow due to a reduction in system pressure causing a temporary sub atmospheric pressure (“vacuum”) in a part of the water system.
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Term |
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Check valve |
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Definition
A check valve allows flow in one direction but stops flow in the opposite direction. It is also referred to as “non-return valve”.
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Term |
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Containment |
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Definition
An option for backflow prevention consisting in confining potential contamination within the facility where the cross-connection arises by installing a protection at the point of service. Ex: check valves in a residential water meter provide containment.
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Term |
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Cracking pressure |
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Definition
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. Also referred to as “opening pressure” and usually measured in inches of water column. To reduce noise and wear a check valve should preferably be selected so that it operates in a fully open position in normal dynamic flow conditions.
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Term |
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Cross connection |
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Definition
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 hose connected vegetable spray can create a temporary cross-connection.
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Term |
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Cross-over flow |
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Definition
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.
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Term |
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Cv factor |
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Definition
The Cv constant is the number of US gallons per minute that will pass through a valve with a pressure drop of 1 psi. The Cv factor is most meaningful when applied to valves that are either fully open or fully closed without the aid of the fluid flow. Although it does not ideally apply to spring loaded check valves the Cv constant is still frequently used with check valves to compare flow capacity between different models and sizes.
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Term |
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Delta P |
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Definition
A term commonly used to refer to the pressure drop (or headloss) through a piping component such as a valve.
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Term |
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Dynamic Pressure |
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Definition
Refers to the pressure level (psi) when there is an actual flow.
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Term |
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Effective opening |
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Definition
In faucets, fittings or valves refers to the smallest orifice in the fitting body or in the supply piping to the fitting. In general, the greater the effective opening, the lower the headloss.
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Term |
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Flood level rim |
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Definition
Top edge of a kitchen sink, lavatory bowl or tub over which water would overflow.
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Term |
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Foot valve |
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Definition
A type of check valve combined with a strainer used to pump water from a tank or reservoir.
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Term |
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Gauge pressure |
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Definition
Pressure read on a pressure gauge. Measures only the amount of pressure above (or below) the atmospheric pressure. Pressure values given in this website are gauge pressures (psig).
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Term |
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Gravity backflow |
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Definition
Refers to a form of backflow due to a backpressure caused by gravity (difference in elevation).
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Term |
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Headloss |
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Definition
Refers to the pressure drop through a valve due to flow restrictions. Usually represented in a curve headloss (psi) versus flow rate (gpm).
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Term |
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Hydraulic shock |
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Definition
Refers to the sudden elevation in line pressure caused by a shock wave created by the sudden change in velocity of a non-compressible liquid such as water. Systems with a fluid velocity over 10 fps are at risk of damaging vibrations due to hydraulic shock.
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Term |
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Hysteresis |
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Definition
Refers to the changes in a performance curve, for instance the headloss curve (psid) of a spring loaded check valve, when plotted against increasing or decreasing flow (gpm).
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Term |
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Isolation |
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Definition
An option for backflow prevention consisting of installing a protection device at each potential cross-connection. NEOPERL check valves are used primarily for isolation purposes. Example: a check valve in a hose connected kitchen spray or handshower provides isolation.
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Term |
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Lip seal |
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Definition
NEOPERL’s molded lip seals are placed inside the check valve body instead of on the plunger as usual with flat seals and o-rings. Combined with profiled plungers in NV/OV check valves lip seals provide optimal sealing performance even in very low backpressure conditions and more effective opening for reduced headloss.
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Term |
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Medium |
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Definition
Refers to the fluid used in the application. NEOPERL flow regulators and check valves are designed for clear water applications (check valves are also functional in air applications).
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Term |
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Opening pressure |
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Definition
See “Cracking pressure”.
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Term |
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Pressure differential |
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Definition
Refers to the difference of pressure between the inlet and outlet of a valve or system.
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Term |
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Static pressure |
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Definition
Refers to the pressure level (psi) when there is no flow.
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Term |
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Tightness in backflow conditions |
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Definition
Usual check valve applications require the valve to shut tight when the flow direction reverses. Standard NEOPERL check valves are 100% tested for water tightness in backflow conditions.
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Term |
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Tightness in the direction of flow |
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Definition
Selected applications require that check valves be tight in the normal direction of flow up to a certain pressure level. The test is usually performed using a vertical sight glass tube to verify that the check valve “holds a water column”, 29” for instance (equivalent to 1 psi).
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Term |
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Vacuum |
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Definition
Refers to any pressure less than that exerted by the atmosphere
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Vacuum breaker |
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Definition
A type of backflow protection device effective at preventing backsiphonage backflow by admitting atmospheric pressure into the system.
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Term |
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Velocity |
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Definition
Refers to the traveling speed (usually measured in feet per second) of the fluid inside the valve. Plumbing Codes recommend a maximum velocity of 8 fps (5 fps in hot water lines) to reduce noise and wear. NEOPERL check valves are safe for use up to 12 fps.
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Term |
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Water hammer |
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Definition
Water hammer is the sound resulting from hydraulic shock (can occur when a column of moving water comes to a sudden stop). Spring loaded check valves are preferable to traditional swing check valves to reduce water hammer.
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Term |
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Water Hardness |
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Definition
Water hardness is usually expressed in parts per million (ppm) of dissolved calcium carbonate. Hard water usually also contains another dissolved mineral, magnesium carbonate. Limestone deposits from hard water (calcium and magnesium carbonates) can affect stream quality in faucet aerators and also cause early valve failure.
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Working conditions |
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Definition
Refers to the usual parameters of the application such as medium, pressure range and temperature range.
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