What is a Backflow and How Does It Work
The most common backflow device is the Reduced Pressure Principle or RP. I will attempt to describe how it operates in easy-to-understand language. I think you will find it is less complicated than you think—certainly less complicated than the picture above with all the pipes going everywhere.
Components of the RP Device
The RP device has several key components arranged in the following order:
- Test Cock #1
- Shut Off Valve #1
- Test Cock #2
- Check Valve #1
- Pressure Relief Valve
- Test Cock #3
- Check Valve #2
- Test Cock #4
- Shut Off Valve #2
- Test Cocks: These are access points used by certified testers to check if the device is working correctly during annual tests.
- Shut-Off Valves: These are used by testers for maintenance or to stop water flow to the property.
- That leaves us with the main components: The two Check Valves and the Pressure Relief Valve.
How It Works
Here’s a breakdown of how water moves through the RP device and how each component functions to prevent backflow:
- Water Entry and Check Valve #1: Water enters through Check Valve #1, which acts like a one-way emergency Door at a school. It opens to let water flow in one direction but locks to prevent it from flowing backward, similar to an emergency door that only opens from one side.
- Pressure Relief Valve: After passing the first check valve, water flows next to the Pressure Relief Valve. This valve detects any reverse flow (water moving back toward the public line). If reverse flow is detected, this valve opens to divert the backward-flowing water outside of the device, preventing contamination of the clean water supply. Imagine a revolving door that dumps anything, trying to go back the way it came outside instead of letting it return.
- Check Valve #2: Finally, water passes through another one-way emergency door, Check Valve #2, ensuring that even if the first check valve fails, there is a second barrier to stop backflow.
By arranging these valves and mechanisms in this order, the RP device ensures that water can only flow in one intended direction, keeping the public water supply safe from any potential contamination.
Why Is Annual Testing Necessary for Secure RP Backflow Systems?
Much like the High School days when the kids in the school would prop open the emergency doors so the bad kids could get in, backflows have their own issues; particles can get lodged in the check valves that can keep them from closing tight, or the relief valve gets fouled, or the springs get weak, and it does not open in time. With an annual test, we can catch these problems before all three components fail. As long as one of the three components works, no backflow will occur.
Anyway I hope this explains the operation of a backflow device. If you have any questions, feel free to contact me at dan@piperh2o.com