Fresh water pump won’t shut off

DanD2

Can you bypass the hot water tank?

Willhound

Check and make sure the pressure relief valve on water heater isn't stuck a tiny bit open.

rmrstlmo

How about putting the water heater in the winterized configuration.  This would completely remove the water heater from the pump system.  If the pump then works properly at least you would have isolated the problem.

Spyderweb

Eureka!!!  Breakthrough!  As if the whoosh from the water heater wasn’t confounding enough, when the shore water is hooked up to boat and turned on, there is the sound of water running, even though none of the faucets are open.  A bit alarming at 1st.  I’m searching all over but can find no water rushing into the boat.  Went down to talk to my dock mate again and walk through what’s happened.  He’s pretty stumped.  He comes over for a listen himself and can’t believe there’s not a flood somewhere.  Kinda a sound like your toilets running at home.

Then he stumbles on the fact this water heater has a heat exchanger and is plumbed Into an engine.  What if heat exchanger is shot (not winterized properly) and so pressurized water from shore is forcing water out of water heater through hose into  engine and then drains back to river through outdrive.  Whooh!

i feel the inlet hose to engine from heater and it’s very cold, as if fresh water is currently running through it, vs. a room temperature hose.  Just to confirm, he pulls hose off engine and sure enough, water is just streaming out of it.  

So to sum up, with pump on, pressure is bleeding off of water heater through faulty heat exchanger, so that pump can never build up enough pressure to shut off.  That was the leak.  So big, yet undetectable because lost water was leaving boat, not going into a bilge.

Solution is to bypass heat exchanger system by doubling back the heater hose on itself, and doubling back the engine hose on itself.  The way we use our boat, though we leave the dock all the time, the bays we go to are 15-20 minutes away, so the heat exchanger never did get me much hot water.  We always heat the water at dock for minimum of 45 minutes and lasts all day.  

Ian

Well done, what a b*&^h to work out.

Dream_Inn

Glad you found the problem!  I guess you are raw water cooled.  On my boat, that is antifreeze that comes thru the water heater (so it'd be a mess).

Spyderweb

Yes fresh water cooled, and last boat didn’t have the heat exchanger on the water heater, so never even considered that.

rmrstlmo

Glad you figured it out....  and a relatively cheap fix.

MarkB

If your water heater tank is full of air, it won't fill by pumping in water. The air is trapped in the top of the heater.  The only way to relieve the air is to open the pressure safety valve until water starts coming out (with your water pump running of course).

Spyderweb

@MarkB but isn’t the pressure relief valve at the bottom?  With air trapped at he top, won’t that still just force water out?

Willhound

Spyderweb said:

@MarkB but isn’t the pressure relief valve at the bottom?  With air trapped at he top, won’t that still just force water out?

That's the drain the pressure relief is up near the top.  Has a little lever on it that is spring loaded. If you lift the lever it lets air out. Every spring when I fire up the water system I leave that valve open until water comes out, then pop it shut. Can't compress water but you can compress air so any air in the tank and the pump won't shut off. 

Spyderweb

Just looked at a picture of my water heater and you're right, pressure relief is near top.  In my mind I had it lower.  I actually did spring it open during this debacle this spring to see if air would come out but it was just water.  I like your idea of leaving valve open during Spring fill till water comes out.  

randy56

Beware of over use, flipping those pressure relief valves open and closed to many time's as the will fail to shut off completely. They are not made for that type of use. Being spring loaded. I'm experienced in have to change them. Open the hot water at the faucet.

Spyderweb

@randy56 Good advice.  I'll continue then to just open the hot water at faucet.  Thanks.

Willhound

I have to respectfully disagree with Randy. The outlet for the tank is lower than the vent. The top half of the tank will still be air. You need to vent that at the tank it will not work it's way out at the faucet.

MarkB

randy56 said:

Beware of over use, flipping those pressure relief valves open and closed to many time's as the will fail to shut off completely. They are not made for that type of use. Being spring loaded. I'm experienced in have to change them. Open the hot water at the faucet.

Hot water at faucet will not fill the tank in my opinion ... the hot water supply is located near the bottom of the tank, and all the air at the top won't have any way of getting out. That's as far as I remember.  I don't think opening that flap once a year will cause any damage. PSV's are made to open and close multiple times.  What you don't want to do is change the spring tension setting.

Liberty44140

The dock water pressure (regulated at my hose input) fills my water tank just fine. Never had to release air at spring start up via the valve. Of course a large air gap comes out of the faucet. I bypass and drain the tank in the fall. Then in the spring after running all antifreeze out of lines reconnect the hot water tank and all good. Could just be my set up..... 

Ian

I am similar to @Liberty44140, just purge the air at lines and tank fill up.

randy56

Mine also was like @Liberty, Air was never a problem. I did forget that the hot water comes out of the bottom, not like at home. 
Age is showing, 

Willhound

The issue I've had the last 2 years running is that if I don't open the pressure relief to let the air out the hot water tank only fills half way at which point either the high temp reset button kicks out, or I only get lukewarm water because the cold is coming in the inlet and right back out the tank since the top half is all air. Someone on here (Sorry, can't remember who and too lazy to look it up) suggested the  method I now use and no problems ever since. If you ever drain your hot water tank at home to clean out sediment the procedure to refill it is the same. The air in the tank needs to be bled off because it will only compress so much and then is taking up space.