Help with bilge leaking into water tank

[seahag]

We purchased our boat last April, and during the delivery, our captain said that he found the water tanks were compromised by diesel fuel from the bilge entering the inspection access caps on the tank. There are two of these, made from plywood of all things, and the tank is 100 gallons capacity located in the top of the keel, so basically the lowest part of the boat's bilge area is above the tops of the tank. After discovering the problem, he emptied, rinsed and refilled the tanks twice, and did a temporary resealing of the one hatch that was accessible--the other hatch is under settee floorboards so was not attempted at the time.

We used the boat all season and tried to flush out the tanks twice, but the diesel is still quite prevalent. Our surveyor said we should file an insurance claim. we mainly just want to solve the problem to the extent of being able to wash dishes safely and take showers without smelling diesel. We don't plan to use it for drinking at any rate.

What I am wondering is if there is a suitable cleaning agent to flush out the lines and the tanks to make it tolerable? After that, is there a membrane that we could paint a new liner on the inside of the tank to make it more pure? I know we have to make new hatch covers first and get that sealed before anything else so no need to advise on that. I have looked into getting a bladder but have not found any that are close to 100 gallons, so would it be feasible to use 2 or 3 of these and somehow connect them if that is the route to go?

Lastly, is the whole system permanently compromised to the point where we would need new lines, faucets, etc. or can that be flushed?

Thanks ahead for the advice.

[boatman61]

Forget flushing.. get the appropriate shape/size bladders and fit them inside.

[Cheechako]

Hmmm... not sure. But if the tanks are good I would try pressure washing them out with detergent. The detergent will cut the oil. Then I would replace the water lines. You could even fill them with water and detergent and use the boat for a month. All the sloshing around might help.

[boatman61]

Originally Posted by boatman61

Forget flushing.. get the appropriate shape/size bladders and fit them inside.

And obviously replace the pipes..

[Island Time O25]

How did the diesel escape from its tank? And did you resolve the issue of the leaking diesel first?

[seahag]

Originally Posted by Island Time O25

How did the diesel escape from its tank? And did you resolve the issue of the leaking diesel first?

Very good question. We don't know. We do know there was some diesel in the bilge both before and after the delivery, and some seems to end up there with regular use. I am not sure what's going on with that as we have not found a leak, and the engine starts really easily so i don't think it's a fuel leak ahead of the injector pump but we are experimenting right now with shutting the lines off as close to the tank as possible to see what affect that may have. We live a pretty long distance from the boat and it being winter can't do as much right now but want to make a plan for next time to solve some of these issues.

[bsurvey]

cut out the swash plates if any and put in a bladder bag you will never get the taste out of the rubber lines and painting the inside is a waste of time

[Island Time O25]

Seahag, I just noticed that you're in Alaska. So most likely you have a heater on board. Is it a diesel heater? If so if it draws from the main diesel tank it may be producing that leak somewhere along the way. Also there could be an overflow line breakage but which leaks only at a certain angle of heel. Don't ask me how I know. Or poorly fitted/closed tank access hatch.

Doesn't seem right to spend time, effort and $$ flushing out the water tank before resolving the diesel leak issue.

[Xthewater]

Question: How old is the boat and what material is the fuel tank made of? If aluminum it may be suffering from poltace corrosion and have a pinhole leak which would require replacing.
2nd issue is bilge leakage which would be next priority because whatever is done re the water tank is a bandaid.
3rd either bladder or some kind of impermeable (paintable or sprayable) liner though I lean more towards bladder solution to keep out any further contamination.
Sounds like you have a domino effect situation which needs resolving at the beginning i.e. Fuel.
Best of luck.

[rwidman]

Originally Posted by seahag

................... Our surveyor said we should file an insurance claim. .............

How could you file an insurance claim, especially on a boat you bought with an apparent defect?

The surveyor should have warned you about the problem and you could have taken the cost of repairs off what you offered.

The right way to fix this is to replace the tank and the plumbing if needed.

[seahag]

Thanks for all the suggestions, it sure helps to form a plan. I was really hoping not to replace the lines, as they are going to be really tough to do running under parquet floors, and other inaccessible areas.

The boat is a fiberglass 1983 Canadian built rig, and yes it does have a diesel heater. That is fed from its own tank. I don't think the leak is coming from that but there are areas where I can't see the line for that either, which makes it a possible culprit. Probably the best way to find out is I can fill the tank to a mark when we leave next time, and inspect on following trip to see if it loses any level?

The water tank is fiberglass. I have no idea what the history of the plywood covers for the tank access is all about. It seems like a terrible idea to me. The PO in many parts of the boat had used a really unsatisfactory sealant, some white crumbly crud, and it caused other leaks as well.

Everyone, thanks again for your help--I do appreciate the time.

[seahag]

Originally Posted by rwidman

How could you file an insurance claim, especially on a boat you bought with an apparent defect?

The surveyor should have warned you about the problem and you could have taken the cost of repairs off what you offered.

The right way to fix this is to replace the tank and the plumbing if needed.

Another good question. I didn't think it was an insurance issue. The company, however, is taking it seriously, and if we do file a claim, they are willing to go to the expense of flying a surveyor to our port, and pay for his analysis..., so it must have some merit.

Basically, our surveyor said that since it was no fault of our own that the water was contaminated, it could be a claim. I don't want to risk having our insurance pricing go up though I would like water to do dishes with.

[Glacier Crews]

To answer your last question first: Yes. All the lines and the tank are permanently compromised. You will always smell the diesel. That means you will always be putting fuel on your ... self, dishes, etc. You will never be able to drink from that water tank and you will not be able to sell your boat without disclosing.

I have been researching this issue, with a couple of other people (one in Canada who lives aboard and ran a petrochemical research station in Canada) and another liveaboard in PNW. We have yet to talk to any firm, scientist, expert, etc who was willing to say anything other than "you are never going to get the tank back to rights." The Canadian couple have tried products only available to petrochemical plants to no avail. The few products that will remove, permeate the tank and are a toxin.

Finding and using a bladder works, but you will still have to change out the lines.

You must find the diesel leak.

Whoever surveyed your boat, might be willing to come identify the leak, if you present the problem as one "we" need to solve when you ask about his professional liability insurance (information your own carrier will also want to know.)

One common fix, if you have room, is to convert the tank to carry diesel and replace with new tank and lines.

Good luck.

[roland stockham]

My inclination would be to go with the 'switch it diesel suggestion as easier if there is an alternative location for water tanks. Where are your current diesel tanks? could they be swapped for water?
Wanted to make a couple of points, Plywood coated with epoxy is a perfectly good option for water tanks and a great way to make custom ones. Mine have done 50yrs with no issues and are as good as the day they where built! So plywood inspection covers are not necessarily a problem unless done badly.
The second point is implies in every thing you say. If re-plumbing is such an issue due to access how are you doing to fix n emergency at sea. Do you have access to the hull sea-cocks etc as well as fuel and water systems that would enable you to quickly deal wit an emergency that could threaten the boat or crew (by loosing all you fuel and water!). While fixing this problem may be worth looking at the whole layout so you finish up with an all round better boat.

[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.