Immersion heater filling bilge with water

[jwilson]

I'm not so sure about that? How would the valve seat have got any dirt into it unless it was opening. And if it was opening, why would it be doing that unless the tank is being overpressurised for some reason?

Richard

It does open occasionally, to do it's job, release excess pressure. http://www.jabscoshop.com/images/WATER SYSTEM.jpg shows a good system, but most yachtbuilders omit the expansion tank, hence occasional overpressures.

The makers instructions for the PRV say clearly to click it round to operate it "at least once a month".