levitating water heater

[Tim Mills]

This is a first for me.

On our new-to-me H41DS I was working in the settee compartment installing an air conditioning relay next to the water heater and inverter. I noticed that the water heater was crooked and one corner was lifted up 1-1/2" and a screw securing the water heater base pan was ripped out. First I thought that the water heater pan (which is recessed into the floor a few inches) had broken loose during a recent brisk sail.

It turns out that when I completely fill my fresh water tank located on the port side directly under the water heater, the top of the fresh water tank expands and rises up and pushes against the bottom of the water heater pan with enough force pushing the entire water heater assembly up and pulling out the screws securing the pan. I ran some water out of the kitchen tap and the water heater settled back down flat and I re-secured it.

What a crazy thing. Is this a thing for others?

 

[kloudie1]

Fresh water vent open and not plugged with spider/mud dauber debris?

 

[Tim Mills]

Its open and vents fine. The tank was full all the way up to the deck fitting. This probably creates about another 2 psi in the tank or almost 300 psf.

 

[JamesG161]

My 100 gallon plastic water tank balloons upward, if over filled.

I now meter in the water and have a good level transmitter to avoid over fill.

And yes an over fill can pressurize by ≈ 1 psi but spread over the top surface of the tank is not much up force on a single point.
Jim...

PS: Check your forces by pumping out some fresh water.