Fresh Water Leak in bilge

[alvasurg]

2004 460 Voyager owner. I'm stumped. I constantly see 1 or 2 inches of water in my bilge. When I turn on the "pressure water pump" and leave it on, It'll empty out the fresh water tank in one day. Likely into the bilge. The Aft bilge pump then pumps it out. However, when I connect to dockside water and turn the pump off, the bilge has much less water in it. I have a Siren Marine system that tells me when the pump goes off, so I know when it cycles.

Any ideas as to how I go about finding the leak source? I'm aware that many times it's the water heater, but why doesn't it leak when connected to dockside water?

[bud37]

There really is no quick answer to this. It will require some time consuming inspection.

This is how I would tackle it........First empty your onboard tank, while emptying check the fresh water pump and surrounding fittings, then dry the bilge completely dry, shop vac if you have to.....then connect only the dock water, pressurize, get a bright light and check all your fittings with the water on but no taps open, put your fingers around each fitting if possible, put dry paper towels in all the sinks. If you suddenly see water in the bilge, try to isolate the direction it comes from to help find the leak....same goes if you find wet paper towels in the sinks, shower drain ( that should be obvious ).....give it some time.

If at this point if the bilge is still dry then turn off the dock side water, refill your onboard tank and do exactly the same thing with the onboard system on.....you see there may be a difference in operating pressure here, perhaps causing a leak that was not present with the dock water if it was a much lower pressure. You will also check the tank, the pump and the fittings between the tank and pump, especially the screen filter.

Good luck and take your time.

[km1125]

What Bud says is a good direction to start.

It could well be that you have one leak and the difference is caused by the pressure difference between your shore water and the potable pump pressure. You could also have two leaks, one between the potable pump and where the shore water ties into the system and then a smaller one after the shore water ties into the system. I had a pinhole in a fitting once that was so small I couldn't actually see the stream of water coming out, but could feel it on my hand. You could see where it was getting the bulkhead wet about a foot away.

[Viper]

Ya it's a matter of getting your head in there and eyes on all your plumbing hardware. There will be some not so easy places to access but typically the culprits are fittings, fixtures, hot water heaters, ice makers, washers, tank, etc. Sometimes the hardest ones to find are shower faucets where the leaks are behind the shower wall and difficult to see.

You haven't mentioned whether your pump cycles periodically with the faucets turned off. If it does, that's a dead giveaway that there is a leak on the pressure side not withstanding the ice maker calling for water, so turn the ice maker off if applicable. If there is a leak there, it'll still leak on the supply side with the icemaker off. A cycling pump could also mean a bad check valve and system pressure leaking back to the tank but given your symptom, I don't suspect that's the case.

If the leak is big enough to empty your tank in one day it should be a pretty obvious leak. The only section of the system that's separate from the dockside supply would be your tank and the plumbing between it and your pump providing no modifications have been made in the past so you can start your search in that area if you're convinced the problem isn't present when the pump is off and you're running off dockside pressure.