Aft tank leak

[SV Pretty Lady]

I filled up the aft fresh water tank for the first time Sunday. Today, I noticed water all over the floor under my mattress. My mattress is a custom foam that rests on vented tiles to allow air flow. The bolts that hold the wall are saturated and continue to leak, especially the last few bolts closest to port side.
What causes a leak like this? I looked at it the best I could but didn't see any visible leaking. I dried off the seam where the water is coming in, but it keeps leaking. Any ideas?

[Jon W]

I'm not sure after reading your post. Have you removed the wood from the aft bulkhead and looked at the tank?

The first possibilities that come to mind are

1) The fill hose or the vent hose connecting to the tank leaks allowing water to run into the aft cabin.
2) The discharge hose at the forward end on the bottom of the tank is leaking.
3) One of the screws holding the wood to the bulkhead or a screw holding the plastic cover to the wood, pierced the plastic water tank and is leaking.

[scgunner]

      I had the same problem last summer. What caused my leak was a fracture in a corner at the top of the tank. The tank would leak down and fill up the pan the tank sits in which is tilted slightly aft, when the boat heels the water runs to the low side and pours out through the wood bulkhead into the aft cabin. Sound about right?

       You'll have to remove the bulkhead, pull the tank, find and fix the leak. I just used a hot screwdriver and melted the crack closed. Also, I drilled a couple of holes in the low end of tank pan so should it develop another leak the water can drain through the pan and run down to the bilge instead of into the aft cabin.

[Ron Hill]

Guys : There has been many a note in the Mainsheet tech note to be careful when replacing the aft panel and the "dog house" on the overhead coving the steering!!  There are short screws and long screws

If you take a long screw to secure that dog house to the aft panel it WILL puncture the aft water tank.
To preclude that I glued a couple of nickels (5 cent pieces)on to the aft water tank as a "just in case" I used the wrong LONG screw!! 

A few thoughts

[Jon W]

For the "dog house" I got rid of the wood screws and replaced them with T-nuts in the wood panel and used SST machine screws with tef-gel. No more tear outs or risk of puncturing the water tank.

[SV Pretty Lady]

Well, I think I found it. One of the PO's along the way replaced the second to last screw (where my water is seeping in to the crack between the wall and frame) with a much longer screw than the rest. I sailed the boat before I put water in the tank (for the first time since I bought the boat), so it couldn't leak yet. I didn't notice the leak until a few days after and there was black mold already growing on the vinyl cover of mattress where the sheet soaked the water.

I didn't take the port wall off so I wasn't able to completely take off the aft wall, but I looked around and did notice on top of the tank, where the gauge unit is, some water around the seal. However, I doubt it is enough to have filled my cabin with a pond, and continue to try to fill it. I am pretty sure it is the long screw that did it.

Gluing nickels is a brilliant idea. I am going to do that when I take the wall off today.

I am sort of regretting putting in a 7" heavy foam/memory foam mattress as I am preparing to do this job today. It's like wrestling a whale and it will be interesting to see how I will remove both walls. Will probably have to do the job in steps....roll mattress up one way, then roll up the other way.... As a major inconvenience as this is, since I live on my boat, tonight I will enjoy the comfort of my mattress and this job will be a distant bad memory. lol.

[Noah]

I am a confused by your statement about there being water "where the gauge unit is on top of the tank." Do you have gauge on your water tank? The long screws that could cause a puncture in the plastic water tank are located on the "doghouse" which is the gelcoated fiberglas cover that hides the steering cable access. It is located centerline and screws into the cockpit floor from below and into the center of the aft wood bulkhead.
If the screw punctured the water tank the hole would be near the forward top center of the tank.

[pablosgirl]

We had a leak in are aft tank from th PO putting long screws in the "dog hous" .  The screws were just long enough to touch the tank. A few years of scratching back and forth made two holes you could slide a popcicle into.  Blamed the leak on the ports till one day I had the cushions out to adjust the stuffing box and just happened to fill the aft tank to overflowing the deck fitting.  A little while later I went to replace the cushions and found water leaking from behind the aft bulkhead.  I took the bulkhead out and found the two holes within an inch from the top of the tank.  Only leaked when the tank was mostly full.

I did some research and found that the only way to properly repair the tank was to plastic weld it.  I found this out by calling the manufacturer of the tank.  They quoted me $40 to repair the tank by "spin welding " it.  I just had to bring the tank in.  They are in CA and I am in TX.  The shipping to and fro was going to be about half the cost of a new tank.  They then recommend using a heat gun and some scrap tank material which they set me for $20, to weld the tank.  I watched a few YouTube videos to get the technique down .  It took about 15 minutes to make the repair.  I did not have to remove the tank.  That was over a year ago and the tank is leak free.  The hardest part was living with the aft cabin in disarray while we waited for the tank scraps to arrive.

[Ron Hill]

Guys : Paul is correct about the right way to fix a hole in one of the water tanks. 

If it's a small hole some butyl rubber on a flat head machine screw will also work!!

A thought

[scgunner]

    Whatever kind of leak you have and however you choose to fix it I would recommend drilling the drain holes in the rear water tank pan. My leak was caused by a fracture in a corner of the tank(not screw holes)and while I fixed it and it doesn't leak that doesn't mean the tank can't develop a new fracture. If it does the drain holes will prevent the leaking water from getting into the aft cabin until the new leak can be remedied.

[Mas Tequila]

We had a foot long crack in our forward water tank and we were simply going to replace it however the $200.00 shipping cost for a new tank seemed a bit crazy so I bought a Hobie - Kc Welder Pro and polyethylene rod and welded it up. It worked great and after a year not a drop has leaked.