Leaking Beneteau Water Tank

[kloudie1]

My buddy’s 2000 Beneteau 42, center cockpit, fixed dodger, cruiser has a leak in the starboard forward water tank. We’ve eliminated all hoses and stuff since they all come out of the top of the tank and are easily seen. The tank slowly leaks to the bilge and we’ve eliminated other water sources by dying the water and having the dyed water show up.. This happens with the water pressure turned off or on. The water shows up in the forward limber hole in the liner structure. We are pretty sure that the leak is in the tank itself, which is molded into the liner and has a lid glued onto the ledge in the top of the molded tank. The lid is not leaking. Beneteau confirms that the top of the tank can be removed if carefully pried off and can be reused after cleaning. They cannot tell us what is holding it down..
Has anyone had the same problem and how did you deal with it? Is the lid held on with elastomer or resin? How did you take the top off? Our plan is to get in the sealant groove and remove what we can see. Then attack the sides with a pry tool and possibly a heat gun to get the sticky to release.. ??
The picture is the top of the tank, looking forward on the starboard side, bunk support board removed. The boat is in Oriental NC (many hours away) , and we are trying to get a grip on how to get the top off before we get there.

 

[Mike B]

Just a thought for what it's worth. If you can't get the top off you might check into the availability of adding an inspection port. So rather than damaging the lid, cut a new hole that can be resealed with an removable inspection port. Good luck.

 

[Tim R.]

Good idea on the port Mike. That is what I would do. In fact having 2 of them makes it even better. Now you can look in one while having your hand in the other.

 

[sailaway78]

I would first

I would first fill the tank, and let it leak down till it stops leaking. This will give you the exact elevation of the leak. If it's in the bottom, it will leak all the way to dry. If it leaks down to half you know the leak is at the half point. Will make it much easier to find, than emptying the tank first, and having to inspect the entire tank for the leak, which may be hard to spot.

 

[larryw]

My Bene 400 had a problem with water tanks apparently leaking when being filled. It wouldn't come out the vent, but leak into the bilge. I finally just started to monitor it, and when the gauge indicated almost full, stopped adding water. I think it was in the hose attachment points though, cause they did all tighten up. My next step was the inspection port and the appliation of a bead of Marine-Tex on all the interior seams, but it didn't come to that.

 

[kloudie1]

Thanks, Guys.. We do know that it stops leaking when the level drops to about ¼ full. We’ve not seen any water leaking around any of the hoses .. The only hoses connected to it are top entering and are shown in the picture. One of the things we don’t know is if the water is contained within a depression in the liner or if the liner is bonded to the inside of the hull there, and the inside of the hull skin forms the bottom of the tank.. When we get a chance to put the mirror inside, we’ll be able to figure that out. My guess is that before the liner was put in the hull, a screw hole was drilled in the wrong place.. Should be easy to fix when we get the top off. We had not considered adding a big port but that may be easier than trying to pry the top off. That sounds like a “plan B” if we can’t get the top off fairly quickly. I think we have plenty flat surface to do that..

 

[Mike B]

FYI I think you'll find it's a seperate tank sitting on top of the hull liner or some sort of support system. Beneteau doesn't glass tanks into the hull.

 

[Barnacle Bill]

What's the tank made out of? Aluminum? Plastic?
The trouble with a number of manufacturers is they seem to build the boat around a component and never consider that some day the thing has to be replaced and hence removed. So, when buying a boat, don't just look at the pretty interior, wonder if you can also get to the stuff hidden by the glitz. Not enough info for me to comment, but will if I had some photos or a better explanation.

 

[windsmaker]

Had a problem with my b38 with fresh water leak.
1) when the starboard tank was over filled.. top of tank leaked.. don't over fill. I have a 6 inch inspection port in my tanks,
2) also had a leak when the pressure water was on ?? After long time inspecting the hot and cold water lines that drove me crazy, it turned out to be a leaking hot water relief value in the hot water heater.. Only leaked at certain times..
Not sure this helps.

 

[agaliha]

Pressure Valve leak, too.

Windsmaker,
I had the same problem on my B361. After searching the entire boat for a presure leak that caused the pump to cycle every 10 seconds, I discovered that the pressure relief valve on the hot water heater was trickling into the bilge (through its overflow hose). Finding a replacement relief valve was impossible. Marine valves open at a lower pressure than household valves and this one was 1/2" NPT where all the new ones I found (Defender) were 3/4" NPT. I finally just bought bushings to adapt the larger valve to the tank. Fortunately, Beneteau left plenty of room around the tank to allow room for this.
Agaliha

 

[kloudie1]

BENETEAU 42 Clipper TANK LEAK Finalized

BENETEAU 42 Clipper Forward water tank Leak
Talked to the Beneteau expert in Charlotte and he said we would not be able to get the lid off of the tank. We cut a hole in the tank and found the tank was made into the hull and liner. The bead of 5200-like material was about an inch and a half wide so there was no chance of levering the lid off. The lid is 1” balsa core with 1/8” fiberglass top and bottom. The tank was formed, I think, by putting a sheet of random glass matting over the hull and using that to seal to the liner, after the liner was in place. The hole we found was a result of poor workmanship by the builder. There was cracking and porosity in the glass matted joint between the liner and the hull. The worst was at the aft of the tank where the mat was glassed over a long, hull strengthening stringer. We got concerned about not being able to get food grade epoxy and so used food grade RTV silicone. The holes were ground out and the cavity filled with silicone. The tabbing elsewhere in the tank looked to be good enough for strength so we did only leak repair. A three hour full tank test after the repair showed no leaks..
Pictures are of the tank with the water and dye in it for leak testing. Other is of the inside, looking aft. The matting over the hull and tabbing onto the liner can be seen at the bottom. The leak was where the dye is oozing out at the corner of the aft tank wall and the corner of the stringer.

 

[Mike B]

Re: BENETEAU 42 Clipper TANK LEAK Finalized

Glad to see you found the source of the leak. How are you going to close the tank back up? BTW I was surprised to see Beneteau glassed the tank in, as I didn't think they did that. After reading your posts I've found other Benny's where they've done the same thing. Learned something new today

 

[kloudie1]

Yeah, apparently they did this on only two models and have discontinued that practice. This boat is a 2001 model. The top is still off because it was cold enough in Oriental NC that we didn't want to deal with the condensation. First time I've looked out of a port and seen snow ! Anyway, we cut the top at a 30 degree angle so it will sit in the hole. The plan is to put 2 aluminum angle braces across the cap extending about 3-4 inches onto the lid. These will rest flush with the top and hold the plug up. The raw cut edge will get a BIG bead of 5200 before the plug is put back into the hole.. The trick is going to be to seal it well enough to keep the balsa core from seeing water. Probably going to trowel on a thin layer of 5200 on both faces of the cut, let that set a day and then glue the thing back in place. The angle will remain screwed across the plug and tank top. Pictures are of the hole opened up and the silicone goo plug in the hole.

 

[Mike B]

Sounds like a plan. Have you given any thought to using silicone rather than 5200 to reseal it? That way if necessary you could remove it again.

 

[kloudie1]

Yeah, we thought about that a lot but the top is big and flat and we want a lot of strength in the bond. Didn't want it to pop loose from the 500+ pounds of water in there sloshing around. The initial hole that was drilled to get the jigsaw blade in, will be plugged with silicone and since the joint will be visible, we figured it would be pretty easy to cut on the same line through the 5200, if necessary.

 

[Mike B]

Hopefully you'll never have to go back in. Good luck with it.

 

[mac1840]

Flexible insert?

Yeah, we thought about that a lot but the top is big and flat and we want a lot of strength in the bond. Didn't want it to pop loose from the 500+ pounds of water in there sloshing around. The initial hole that was drilled to get the jigsaw blade in, will be plugged with silicone and since the joint will be visible, we figured it would be pretty easy to cut on the same line through the 5200, if necessary.

Have you considered just putting a bladder in the old tank and leaving the panel as an access point? It would elminate your concern over sealing the balsa core.

Mac

 

[sailingdog]

I would refrain from using 5200 or any sealant that is not approved for use with potable water systems on a water tank. Many of the commercial sealants have fairly toxic components, including cyanates in many cases. Using such chemicals on a potable water tank is both foolish and dangerous.

From the 5200 MSDS sheet:

Contains a chemical or chemicals which can cause cancer. TOLUENE DIISOCYANATE (26471-62-5): Persons
previously sensitized to TDI or other isocyanate may react to subsequent exposures of concentrations well below the TLV. These
symptoms which can include chest tightness, wheezing, cough, shortness of breath, or asthma attack, could be immediate or delayed
for several hours.

That basically means the sealant contains a CYANIDE based compound.... Do you really want that in contact with the inside of the potable water tank????

Yeah, apparently they did this on only two models and have discontinued that practice. This boat is a 2001 model. The top is still off because it was cold enough in Oriental NC that we didn't want to deal with the condensation. First time I've looked out of a port and seen snow ! Anyway, we cut the top at a 30 degree angle so it will sit in the hole. The plan is to put 2 aluminum angle braces across the cap extending about 3-4 inches onto the lid. These will rest flush with the top and hold the plug up. The raw cut edge will get a BIG bead of 5200 before the plug is put back into the hole.. The trick is going to be to seal it well enough to keep the balsa core from seeing water. Probably going to trowel on a thin layer of 5200 on both faces of the cut, let that set a day and then glue the thing back in place. The angle will remain screwed across the plug and tank top. Pictures are of the hole opened up and the silicone goo plug in the hole.

 

[Steve Dion]

Have you just considered glassing the piece back in place. This would be the best method to reseal it to a "factory" like repair and be sure that it will be there in the future. You can put in an inspection port that can be removed for cleaning and access. If you decide to get an inspection port, be sure that it is a high quality water proof one with an o-ring.

 

[Stu Jackson]

Good idea, but try it the other way first (for the "next time")

I would first fill the tank, and let it leak down till it stops leaking. This will give you the exact elevation of the leak. If it's in the bottom, it will leak all the way to dry. If it leaks down to half you know the leak is at the half point. Will make it much easier to find, than emptying the tank first, and having to inspect the entire tank for the leak, which may be hard to spot.

Start with an empty tank and slowly start to fill it. Just in case. Glad you found it, good detective work!



Repeat rant: the ONLY place 5200 should be used on a boat is the hull to deck joint (and maybe to fix a "Catalina Smile," but then it'd be a pain to drop the keel if you ever have to).