A Backflow preventer prevents polluted fluids or gases from entering a potable water supply system due to back siphoning or backpressure. In general, the suitable device to utilise is determined by the degree of danger created by the cross-connection.
Additional factors to consider are pipeline size, location, and the probable requirement to test the devices regularly to ensure effective functioning. Backflow preventers are legally mandated and must be installed in compliance with local plumbing and construction rules. The following are some of the most frequent kinds.
The Different Types of Backflow Preventers
An air gap, unlike other forms of backflow preventers, is mechanical. An air gap may be produced in sinks and bathtubs by raising the faucet high enough above the flood rim. In cases when this isn’t possible, an air gap device is utilised.
Water softeners and dishwashers both use air gap devices. Whether created by correct fixture placement or the use of a device, the air gap creates a physical barrier between the water supply and the non-potable water container.
Hose Bib Vacuum Breaker
A hose bib vacuum breaker, as the name implies, is a type of backflow preventer often used for outside faucets where a hose attaches. With its single spring-loaded check valve, this threaded device may be fitted into the faucet and prevents backflow.
The valve opens and shuts in response to water pressure, enabling water to flow only one way and preventing non-potable water (e.g. from a pool, puddle, or pail of soapy water) from back siphoning through the hose’s end.
Atmospheric Vacuum Breaker
The atmospheric vacuum breaker, also known as the AVB, is usually composed of brass and bent at a 90-degree angle. A poppet valve is located within an AVB and is held up and out of the way by normal water pressure. There is no way for air to get in at this point. When the pressure is lowered and backflow is imminent, the poppet valve closes, and the line is blocked. This process in the backflow preventer this accompanied by the introduction of air into the system to break up any back-siphonage.
These devices cannot be deployed in an area with air pollutants that should not enter the water since they act on atmospheric principles. Another drawback of this technology is that the protected potable water line must be located upstream from the non-potable water source. Irrigation systems are the most prevalent use for these valves.
Pressure Vacuum Breaker
The mechanism of pressure vacuum breakers (PVBs) is quite similar to that of AVBs. The PVBs, on the other hand, features a spring-loaded poppet valve. PVBs may be put in systems where the potable water line (the protected line) is downwards from the non-potable source because of this difference.
Test cocks with calibrated gauges are generally fitted to these backflow preventers to confirm they are operating correctly. PVBs are most often used to prevent backflow in sprinkler systems installed underground.
A double check valve, also known as a double check assembly (DCA), is a device with two spring-loaded check valves in sequence. Because these two valves work separately, one of the key benefits of having this backflow preventer is that the other may take over if one fails.
Furthermore, if both valves are operational, closing the first minimises the pressure difference across the other valve, resulting in a tighter and more reliable backflow seal. Backflow prevention in fire sprinkler systems is the most typical use for DCAs.
Reduced Pressure Zone device
A reduced pressure zone device (RZPD) is a gadget used to protect people from health risks. Two independently acting spring-loaded check valves are included with RZPDs. A pressure-monitored compartment known as the “zone” sits between these two valves.
A differential pressure relief valve keeps the pressure in this zone constant. In the event that both check valves fail, this third valve will open to the environment. In the same way that double-checks valves function, the two independent valves may take over for each other if one fails.
These devices are regarded as acceptable for the task in circumstances where backflow may cause severe injury – since they can efficiently and reliably prevent back pressure and back-siphonage. This backflow preventer is appropriate for safeguarding drinking water due to its redundantly secure construction.