I have recently installed a tanked water heater. I have installed the safety valve that was inside the package, at the cold water inlet.

Something strange happened yesterday. The city cut the water supply for some time, and I noticed my water meter running backward, at very high speed. So it seemed like water was flowing OUT of my house. I also noticed at a different time that the inox pipe leading to the cold water inlet was actually hot.

So I wonder if I have a problem with my safety valve on my water heater. Here's how it looks:

My safety device

When I look on the internet, safety group actually look bigger:

enter image description here

Is the device I installed a proper safety group? Is there a chance that this device does not prevent the water from flowing back from the tank to the cold water circuit?

  • 1
    What you need is a vacuum breaker, which prevents siphoning the water heater tank. What you show is unclear - the "stock picture" looks like a tempering/thermostatic valve, perhaps, but unlike the ones I've seen in having that valved port, and the thing you installed looks more like a temperature/pressure relief that should typically be installed directly on the tank. Perhaps it's pressure relief only, if instructions were to install on the cold inlet.
    – Ecnerwal
    Mar 31, 2021 at 11:35
  • 1
    What make and model is said water heater? Mar 31, 2021 at 11:40
  • If it is an electric water heater and the tank water level dropped, then the heating elements might be burned up and need replacing.
    – crip659
    Mar 31, 2021 at 12:51
  • 1
    What country are you in? It makes a difference. I'm guessing, but what you have installed looks like a drain valve. Also TPR (Temp/pressure relief) valve are installed on top of the WH, at least in the USA. If you are worried about this happening again, a simple check valve on your cold inlet would prevent backflow. Mar 31, 2021 at 15:01
  • Where I live in Pennsylvania, all incoming service water lines must have a "back flow preventer" installed so that what you describe will never happen. Also most outdoor faucets must also be so equipped to prevent a back flow that could contaminate the water supply when a hose is attached. That device you showed in the picture is not a safety valve.
    – d.george
    Apr 1, 2021 at 10:19


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