Beneteau 36.7, 2005, we got it last summer so still gaining systems experience. Only rarely use the water systems; mostly run empty for racing and occasionally put some in for guest comfort and deliveries. Hot water tank pressure relief valve was dumping every time the fresh water pump is turned on, including when just using cold water with engine off so no heat effect. Removed pressure relief valve, went to the local plumbing store, got the exact same Watts make and model rated for release at 150 psi and 210F, noting that the Atwood Model EHM6-SM hot water tank has a sticker saying a 150psi pressure relief valve must be installed.
Accidentally left the fresh water pump breaker on after finishing the replacement and the next day it was running dry as it had pushed all of the water out the pressure relief valve (good news is the bilge got a nice rinse cycle and the bilge pump works).
1) Brand new pressure relief valve is faulty - the guy at the store says in 25 years he can only remember that happening a couple of times.
2) The system is somehow building up over 150psi and the valve is doing its job so the pressure cutoff switch on the water ump need replacing - holy smoke that would be impressive and blowing apart faucets etc. wouldn't it?
3) There is some other plumbing mystery going on that someone here can point me to.
I have picked up a 0-200 psi pressure gage and intend to test the pressure at the outlet where the pressure relief valve is installed, and other points as appropriate. If the hot water tank fitting is showing a normal 35-ish psi, then it's a faulty new pressure relief valve...unless I am not thinking this through correctly?
Any advice before I dive back in on the project? Thanks.