What’s Inside a Boiler? - Part 2: Pressure Relief Valve If your boiler pressure keeps dropping, you keep topping it up, or you have water dripping outside from a copper pipe, the PRV is one of the key things to check properly. It is a safety device designed to protect your boiler and heating system from dangerous pressure levels, but once it has opened, it can sometimes fail to seal again. In this guide I’ll explain what the PRV does, why it activates, why it can start leaki