Water tank leak

[BugOutBoat]

Leaking water tank or hose

We have a leak in either our water tank that sits under our 2001 Hunter 460, Nav station or in a connecting hose. Would anyone have experience on where to either look for a leak in the hose or, if necessary, remove the tank, hopefully without having to tear apart our nav station and bathroom. We are liveaboards.

 

[Terry Cox]

Leaking water tank or hose

Had a water leak experience a few years ago. Wrote an article about it here: https://hunter.sailboatowners.com/mods.php?task=article&mid=45&aid=8246&mn=42

First consideration would be a leaking fitting, that is if you have ruled out rain water. Big leak, small leak, what are the symptoms? Fresh water building up in the bilge, pump cycling? Aluminum/plastic water tank? Can you tell where the water source is coming from?

 

[JamesG161]

It would be very rare to have a water leak from the tank.

Do you have an Accumulator in the water system?
If yes, that is the most likely spot for a fresh water leak.
Jim...

 

[BugOutBoat]

We don’t have an accumulator water system. We’re seeing water dribble out from under the tank.

 

[BugOutBoat]

The pump cycles but even with pump off it still leaks. Plastic tank. It’s a small stream. Bilge pump cycles when we first fill the tank.

 

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[Terry Cox]

We’re seeing water dribble out from under the tank.

Does the tank have a removable inspection port? If so you might consider a repair rather than a replacement. A PO used a non-toxic sealant to coat the inside of his tank (aluminum in this case) rather than replace it. Seems to have worked. His project detailed here: https://hunter.sailboatowners.com/mods.php?task=article&mid=45&aid=100061&mn=42

 

[Mikem]

If it is coming out from under the aft tank it could very well be the fill pipe to that tank. You can remove the deck plate under the nav table. The teak and holly deck plate is supported by another plate that is also removable. My fill pipe (hose) never mated with the side of the tank from the factory. I blanked that off and cut a hole in the top of the tank and put the pipe in that way. NO more leaks. Now for the first time since 2003 I have a dry bilge. FYI this only happened when filling the tank or with a full tank on port tack. I'll try to find some pictures for you.

 

[SG]

The pump cycling should have nothing material to do with a (smallish) leak "upstream" to the tank. The pump will generally cycle if there is a leak "down stream" that causes the pressure between the pump and supplied fixtures to drop.

The first likely sources, as MikeM points out is often the fill. That's easily enough ruled out by dropping the water level to below the top of the tank, drying things out and see what happens. If it's the fill, then there are different approaches to solving the problem.

You want to rule out other sources of "fresh water" (ports, etc.), that too should be easy if you'll dry-out, then make sure you don't send water from some source (other than the discrete flow from the tank to the water filter.

Then, I think you should start searching BACK up steam. toward the tank. It's possible to have a seam failure in a tank (If that's the case, the tank has to come-out). But don't look there first.

There are fiber optic dvices that allow you inspect inside walls. With a small mobile phone with a camera on it, you can sometimes position things to take pictures; or, you can sometimes use mirrors (some on extensions like dental tools) that will allow you to view into otherwise difficult spots.

There is no "magic bullet". It's just an organized search that is likely to reveal the culprit(s).

 

[BugOutBoat]

I thought the same thing. I pulled up the deck plates under the nav station and the fill and vent were dry. I also ran my fingers and hands along the outboard cable way where the hot and cold lines were ran and it was dry also. There is very little space under the head that sits over the tank. I’m hoping I can pull the toilet and the flat plastic plate it sits on is removable so I can hopefully can see better.

 

[BugOutBoat]

Does the tank have a removable inspection port? If so you might consider a repair rather than a replacement. A PO used a non-toxic sealant to coat the inside of his tank (aluminum in this case) rather than replace it. Seems to have worked. His project detailed here: https://hunter.sailboatowners.com/mods.php?task=article&mid=45&aid=100061&mn=42

Unfortunately it doesn’t have an inspection port. The top of the tank has channels in it that prevent installing an inspection port.

 

[BugOutBoat]

The interesting thing is that the tank the water is dribbling underneath is not the tank that is emptying. It’s the forward tank that drains to completely empty. The tank the water is dribbling from stays full. I removed the sending unit from the forward tank and looked inside with water in it and there didn’t appear to be any bubbling like what you might see with a leak. Kinda stumped. I wonder if one tank is siphoning the other?

 

[BugOutBoat]

I removed the nav center decking and sub decking to see if the vent and fill were leaking. Seemed dry and never leaked. I wonder if the vent is clogged.

 

[BugOutBoat]

When we over fill the tank there does not appear to be any vent overboard. It just floods out the deck fitting.

 

[SG]

Sometimes the vent is up high inside the boat or forward in the head or sail locker or...

 

[JamesG161]

When we over fill the tank there does not appear to be any vent overboard

My vent is the vertical Stainless steel grab bar that runs from deck to ceiling. The vent exits under the fiberglass deck cover for the cockpit running rigging lines from the mast.
____
Wait a minute...
We had a leak from our water plastic water tank top edge and from rain water drips down the outside of that tank vent.

We saw that a tank overfill put water in the bilge.

A plastic tank will "ballon" when you overfill it. Repeated overalls cracked the "welded" top seam.
Jim...

PS: The crack was there when we bought our boat. We don't overfill our tank now.