Help with bilge leaking into water tank

[Terra Nova]

Diesel tanks are often installed in hollow keels. Perhaps someone converted a fuel tank to water.

[roland stockham]

Originally Posted by Horus

Lock the tank completely except one entance (hose) and pump the tank with the pump of your dinghy. Don't do it with stormy weather, so you cant hear where the leakage is located!
Good luck.

Good suggestion and if you can flood the top of the keel with an inch or so of water you should see the bubbles.

[seahag]

Thanks again. I'll try to detail all of the latest stuff here in one response. The water tank is the original tank, inside the keel. No, I don't need another diesel tank as we already have 90 gallons capacity in the main tank and 12 in the tank for the heater. It won't bubble now above the tank cover because the plywood has been resealed since this originally happened. So--no more fluid is entering the water system and after we rinsed it twice, it is much less diesellish than when we received the boat, all leading me to believe that for now, at least, it is not getting further contamination although the bilge is still slowly filling with water and some amount of fuel, which we are trying to figure out.

Appreciate the response about the plywood, makes me feel better about the fact that it is there. I've done a fair amount of ply/epoxy work but don't tend to think of that as the best sort of hatch cover in constant contact with water and drying, etc. but if you think it's reasonable, it would be pretty simple for me to do the same thing with brand new material and get it sealed really well on there.

I'm surprised to not find out about any products that could battle the diesel, but if it's just not going to happen, I can deal with the idea of replacing everything. The boat has a complicated plumbing system because some of the lines are defunct, ranging from copper to hose; in some areas it is hard to tell what is all going on as there are extra valves, lines going in mysterious directions.

For the poster who asked about emergency type protocol, thinking maybe I couldn't handle this repair or an emergency because I hadn't torn up my floorboards just to inspect the other tank, well I don't see the relation. I have all kinds of emergency redundant options for getting fluid out of the boat and it has nothing whatever to do with thruhull access, etc. but since you asked I will mention that we accomodated every thru hull in the boat with its own hammer and stop plug, with flashlights located throughout the boat. We have two working bilge pumps and a hose setup that I can throw onto the engine to pump water while it is running. We have an emergency electric pump with decent length of hose that will pump a good amount of water out as long as our 12volt is good enough, and two manual pumps plus the last thing I'd anticipate needing, two dinghy pumps. Hopefully that will be enough to handle what we ever need. The boat was built with a forward watertight compartment in case of a direct collision, and has pretty substantial hull thickness in general. It was a well made boat to start with, though I would say has seen its share of cobbling by previous ownership.

In some ways, it would be a good project for me to replace all the plumbing as then it would be new, and all that extra stuff gone, plus I could run some other wiring that I need in the same area possibly.

Hope that covers most of it-thanks again for responses; a lot of information to work with.

[wooden head]

If you havent yet check your diesel fuel return line. It could be set up to fill the heater tank. This could be an alternate line that is not necessarily currently in use if the valve is closed.

[Lepke]

It's not uncommon to get small leaks in fuel lines where they pass thru bulkheads or even brackets that hold them in place. Usually close to the engine. One easy way is to block one end of each line and put together a fitting with a low pressure gauge and a fitting for a bicycle pump. Apply pressure and view the gauge over several hours looking for a pressure drop. 5-10 psi is plenty. Same way propane lines are checked.
I had fiberglass over plywood fuel and water tanks in several commercial fishing boats. One was 20 years old when I bought the boat. No issues.
One option would be to cut a large inspection hole and re-epoxy the inside after cleaning. Also epoxy the plywood edge. Use a piece of aluminum to close the hole and seal the bolt holes and plate with epoxy.
My experience is you'll never get the diesel taste and smell out with cleaning alone.