Internal Fresh Water Leak

[RM2015A]

I have a 2009 Benneteau Oceanis 46' currently in MARMARIS on the hard.
This past season I have had a frustrating fresh water leak coming from the cross member sub-frame which is located at your feet when sitting at the nav station.
I ran a die test from the water tank">fresh water tank and this was the source of the coloured water entering the bilge. The problem then is to track back to where the water is leaking from without ripping the whole boat apart.
We ran new hot and cold lines to the starboard head as I was sure this was the problem. Unfortunately this did not fix the problem. I have checked all other lines and around the hot water tank and the fresh water pump which are all OK.
Any ideas out there as to how to trace this very frustrating leak would be appreciated.

[nigel1]

I dont know the FW tank layout on a 2009 Bene 46. If it's similar to a 473, the two aft water tanks are integral with the hull, and all the hose connections are at the top of the tank.
Is the water running down from the boats side at the nav station, the only hose's that could be are the fill and vent lines.
Are you able to post any pictures of the area where you suspect the leak is.

[carstenb]

check the bathing platform hose, I had a leak there that drove me nuts for months before finding it

[a64pilot]

Listen for the pump to be cycling on and off, if it's not cycling, then your leak is not on a pressurized line, but some un-pressurized part of the system.

[SkipMark]

Hairline crack in the water tank itself, due to constant flexing in heavy seas, is a known possibility.

[savoir]

Have you given the pressure pump a rebuild lately? Those things typically give around 5 years use before you have to replace all the gaskets and diaphragm or whatever pushes the water.

[onestepcsy37]

I had a very slow leak on an internal water tank, built in as part of the hull. Weeks of searching went nowhere. Fortunately the tank was very accessible. I opened the large inspection port, drained and cleaned the tank, and then painted the whole interior with epoxy. Dried it with heat lamps. End of leak.

Was probably a hairline crack from hull flexing.

[cragowt]

Years ago I had an Endeavor 33. When ever I would return after being gone for a week or so, I would have water in the bilge. I looked everywhere and could not find it. Then one time whiile I was there I heard a noise and it was the relief valve on the hot water tank tripping and that water (warm) was ending up in the bilge. Replaced the relief and Voila! No more leak. Sometimes things can be so simple

[Cheechako]

Originally Posted by a64pilot

Listen for the pump to be cycling on and off, if it's not cycling, then your leak is not on a pressurized line, but some un-pressurized part of the system.

If the pump isn't cycling likely your tank I would think. Unless the out let is not on the top of the tank.

[chrismeikle]

I had a 473 with a fresh water leak. Thought water was getting in thru a hatch.We had freshwater in the Port head - couldn't figure where it was coming from. It took me a long time to find it.
The fresh water tank had been overfilled under pressure by someone - not me!. I always filled the tank by holding the hose over the supply inlet. Beneteau advised that if the fresh water hose is jammed into the inlet pipe the water pressure build up will rupture the tank. Usually on the top surface of the tank somewhere. I had noticed a little fresh water on top of the tank on inspection.
So water was spilling out the rupture in the tank when the boat was on a tack - and gravitating to the port side when on a port tack.
Check your starboard tank by filling it and then going for a decent sail . Check if the tank is leaking when healing.

[RM2015A]

Thanks for the replys.On the 46' the water tank is in the front cabin under the bed. The leak is not coming from the front of the boat. When i did the die test the water is coming from a drain pipe in the cross member beam,how the water is getting into that is the question.Yes the pump is cycling about every 20 mins. I have checked all the lines to the shower on rear transom,thats all OK. fffffffRUSTRATING.

[carstenb]

Originally Posted by RainmanUSA

Thanks for the replys.On the 46' the water tank is in the front cabin under the bed. The leak is not coming from the front of the boat. When i did the die test the water is coming from a drain pipe in the cross member beam,how the water is getting into that is the question.Yes the pump is cycling about every 20 mins. I have checked all the lines to the shower on rear transom,thats all OK. fffffffRUSTRATING.

Well the good news is that now you know it is a pressure leak since the pump cycles every 20 minutes or so. ONly one way. Start disconnecting the pressure hoses one by one and blocking off the valve. Eventually you'll which one is the culprit.

If the pump is only cycling every 20 minutes - it is a very small leak.

The Hot water relief valve frequently gets calcified - that why they leak.