Potable water problems on a 510 Sundancer

Innominata

Member
Mar 3, 2021
41
Boat Info
510 Sundancer 2014
Engines
Cummins QSC 550 w/Zeus pods
I'm having a few problems with my potable water system, and I think I'm in the midst of trouble shooting them. It's a 2014 510 Sundancer.

We spent a day out on the boat recently and emptied a full fresh water tank in a matter of hours despite not using much water, so I started doing some looking around and a found a couple of issues:

1: A very small crack with water misting out at the dock water regulator just inside the transom. I have replaced this with a new regulator and there is no longer a leak there.

2: Water leaking down the flexible hose of the pull-out faucet in the main galley sink. At the time I decided this was being caused by a leak in the flexible hose, which I have removed and ordered a replacement part for, which has not yet arrived. So, I have the shut off valves to the galley sink turned off in the bilge under the galley floor.

A couple of days ago I filled the fresh water tank and left it alone with the fresh water pump off to see if there was any evidence of the tank/plumbing system losing water. It remained full. Today, I replaced the dock water regulator and connected it back to the plumbing system. Then, I turned on the fresh water pump, with the galley lines still closed, to make sure there was no leak at the new connection. That was good, thankfully. But, I noticed that the pump was not cycling off. I let it run for a bit and watched the tank draining down to about 3/4 full in a matter of half an hour or so. I checked all the fixtures around the boat and could find no evidence of anything leaking. Then, I decided to look at the vent for the water fill on the deck, and did not find any water there, but did see water coming out from what I assume is some other vent through the side of the hull just below the galley windows. There are actually two through-hull fittings under the galley sink, and it seemed to be coming from the higher of the two. When I turn the fresh water pump off the water stops coming out from that vent. It seems the fresh water pump is working since it seems to be moving water out of this fitting, whatever it is. Is it possible I just have an air lock in the lines since the line in from the dock regulator was disconnected and I just didn't do a good enough job bleeding the lines? I'm home from the boat now, and didn't think to try this until I got home. Other thoughts?

Also, I should mention that I have had the cabin bilge alarm go off when I get up on plane, that stops after a few minutes. There is a small amount of water in the compartment under the galley floor where all of the shut-off valves. I tightened a couple of fittings and see no more signs of leak there. There is some water in the outer-most compartment under the galley that I think was due to the galley sink leak. I do not see any evidence of water leaking from the through-hull fittings under the galley sink when the fresh water pump is running and water is being discharged over the side.
 
Turn all your valves off on the water manifold. Turn your pump on. It should cycle off fairly quickly. Turn on valves one at a time until you find the one where the pump does not cycle off. Bingo….

Bennett
 
I'm replacing one of my two fresh water pumps as the pump head is leaking. My tell was the forward bilge was kicking on every other day while we were on board for the last 2 weeks.
 
Turn all your valves off on the water manifold. Turn your pump on. It should cycle off fairly quickly. Turn on valves one at a time until you find the one where the pump does not cycle off. Bingo….

Bennett

I neglected to mention that I did try running the pump with all of the shut-off valves at the manifold under the galley floor turned off, and the pump continued to run. I thought this might mean that there is a problem with the pump itself, but it seems to be moving water somewhere since water is coming out of the fitting on the side of the hull.

A friend suggested that it might be coming from the anchor locker, and I don't recall seeing a shut-off for the anchor locker on the manifold. I don't remember where the drain for anchor locker is, or if there even is one, but if it runs down to the side of the boat that might be answer. Hoepfully I'll have time to get back down to it tomorrow to try some more trouble shooting.
 
A common leak area is the water heater relief valve. It's discharge is plumbed overboard. Have you cycled it to verify it seats/reseats?
 
A common leak area is the water heater relief valve. It's discharge is plumbed overboard. Have you cycled it to verify it seats/reseats?

I have not done that because I don't know how to, but this sounds like a promising lead to me. How do I do that? If this is the problem, can I just replace the valve?
 
I have not done that because I don't know how to, but this sounds like a promising lead to me. How do I do that? If this is the problem, can I just replace the valve?
It is the T&P valve just like on your home's water heater. Any RV web store or outlet will have them to fit.
It is a bronze valve with a lever on it. The lever is to test the valve and should be cycled at least annually. On boats they get corroded and eventually will fail and leak. This is what they look like -
kuu11811-2.jpg
 
It is the T&P valve just like on your home's water heater. Any RV web store or outlet will have them to fit.
It is a bronze valve with a lever on it. The lever is to test the valve and should be cycled at least annually. On boats they get corroded and eventually will fail and leak. This is what they look like -
TPValve-5aea6a0aa9d4f90037c28ee4.JPG

Thanks. Hopefully I'll get a chance to try this out this afternoon.
 
I would also add that there is an engine room/bilge fresh water "spigot" that is often overlooked just like the anchor locker one and the transom locker one (at least on my 44DA). Having said that and considering you see water draining out the side of the boat from the galley thru hull fittings, I would certainly get on my hands and knees and go below the galley sink and find out what line that is and trace it back??
 
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It was the T&P valve. I cycled the valve a few times, then turned the fresh water pump on and it held pressure. That's the good news. The bad news is that it only seems to hold pressure when the valve "switch" is turned up, but it still leaks when it's down, so I've ordered a replacement to have on hand. At least I can have the pump on without sending all of my fresh water overboard. Thanks to everyone for the responses.
 
It was the T&P valve. I cycled the valve a few times, then turned the fresh water pump on and it held pressure. That's the good news. The bad news is that it only seems to hold pressure when the valve "switch" is turned up, but it still leaks when it's down, so I've ordered a replacement to have on hand. At least I can have the pump on without sending all of my fresh water overboard. Thanks to everyone for the responses.
Are you talking about the T&P valve on the back of the hot water heater? If so, why was fresh water running out of the thru hull up in your galley area? Your galley has to be 20 feet from the HWH in your bilge?
 
The water heater is under the floor of the lower salon, pretty much even with the galley sink, and the water tank sits just forward of that. The water heater discharge is right under the sink, just like the diagram above. I'm wondering how long the current T&P valve is going to hold out before it fails completely.
 
T&P valves are not reliable once they have any problems.

I would replace as soon as possible.
 

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