what is a backflow preventer

Backflow preventers shut out the entry of contaminants from a non-potable source to the potable public drinking supply; either through back siphonage or back pressure. From firefighting applications to irrigation systems, these devices find great use in the most challenging fields.

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What is Backflow Condition?

Backflow is a situation where the fluid flow reverses unexpectedly. So when the pressure in a pipe changes, the fluid direction is susceptible to change; thereby leading to a high chance of the fluid flowing upstream (user end).

explanation of back siphonage and back pressure

What are Backflow Preventers?

Backflow prevention devices consist of various check valves. These valves allow water to flow in only one way. Additionally, they include pressure-reducing valves to control the water pressure, along with test cocks for maintenance and testing purposes. Furthermore, these devices feature an atmospheric vent to prevent excessive pressure buildup within the system.

In the case of Apollo backflow preventers, they also come integrated with spring-loaded TriForce dual check valves. These valves are accompanied by a pressure differential relief valve positioned between them. Additionally, the assembly includes two shut-off valves with resilient seats, as well as four test cocks for comprehensive maintenance and testing.

Apollo RPLF4A Series Reduced Pressure Principle Backflow Preventers

How Does Backflow Preventers Work?

backflow preventer working mechanism
  1. When water flows in the intended direction, the pressure of the flowing water forces the check valves to open.
  2. The check valve’s design allows water to pass through them easily.
  3. If there is a sudden drop in the supply line pressure, the downstream pressure rises above the upstream pressure.
  4. In such cases, the check valves close automatically.
  5. This closure effectively blocks the backward flow of water and prevents contaminants from entering the potable water supply.

How to Install Backflow Preventers?

Before installing, keep these things in mind:

  • This pressure relief valve should be at least twelve inches above the floor. Also, do not go higher than four feet.
  • Choose a location with adequate drainage for relief valve discharge.
  • Do not install in submerged condition.
schematic diagram

After deciding on the location, follow these steps:

1. First, flush all upstream piping thoroughly. This will remove the foreign matter before installation.

2. Then, mount the reduced pressure backflow preventer in a horizontal position. 

3. Use O-rings to seal the unit.

After installation, pressurise the device while keeping the #2 shut-off valve closed. Bleed the air through test cock #4. Then, open the #2 shut-off valve.

reduced pressure backflow preventer troubleshooting

When Should I Use Backflow Preventer Valves?

Immediately! If you haven’t already installed a backflow pressure-reducing valve, install them now. Each and every workspace should have lavatories equipped with backflow prevention devices. They not only prevent backflow but also protect the users from consuming contaminated water.

The choice of a backflow preventer depends on the level of risk, the application type (residential, commercial or industrial) and local plumbing codes. As a result, Raptor Supplies Limited offers a diverse range of backflow prevention devices from renowned brands such as Watts, Dixon and Apollo.
We serve B2B customers in the UK & Ireland, Europe, GCC / Middle East, Africa as well as Asia who need unscheduled maintenance, repair, and operations (MRO) products. You can also contact us via phone, WhatsApp or email at any time with our 24×7 chat support.

Harshul Gotra

Harshul is a civil engineer and has on-site experience working with MRO tools. He has a knack for storytelling and the ability to explain complex tools.