Water tank issues

Ok I have two water tanks that are built in and original to the boat and both are seeping at the fitting at the bottom of the tank . I have two aluminum fuel tanks that I’m not currently using that are basically the same size as each water tank . I can either repair my built in water tanks or maybe replumb the two fuel tanks for water supply. We only use the water for shower and washing dishes .if I use these two fuel tanks for water I will still have 300 gallons of fuel capacity. Can I flush these two fuel tanks to where they are at good enough for my water needs?
Or would you repair the original water tanks?
I could probably cut the tops out and repair or install a couple of poly tanks in their place. Suggestions please.

Is the fitting that leaks at the bottom accessible? If yes I would try to repair the leak. Is the leak at the tank due to a crack at the fitting?

L

Lou_tribal said:

Is the fitting that leaks at the bottom accessible? If yes I would try to repair the leak. Is the leak at the tank due to a crack at the fitting?

L

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The leak is at the fitting and accessible from the
outside but I’m not sure how the fitting is mounted to the tank, it’s right in the corner . I’m gonna look at it better this weekend.

What material are the water tanks made out of?

I won't say never, but it's difficult to get all the diesel out of the tanks. In Vietnam we had water tanks made out of 55 gallon drums that had contained diesel. They were steam cleaned, used for a short time, re-steam cleaned, soaked with detergent, baking soda, and probably other things I don't want to know about. We didn't drink the water, (we caught rain water) but a couple months later still could taste the diesel in the water. Initially we could feel the diesel on our skin or anything we washed. We paid locals to do laundry. When out in the boats, if we came across a clear stream, we'd wash there.

If you ever sell the boat, it will be easier if you fix it.

Lepke said:

I won't say never, but it's difficult to get all the diesel out of the tanks. In Vietnam we had water tanks made out of 55 gallon drums that had contained diesel. They were steam cleaned, used for a short time, re-steam cleaned, soaked with detergent, baking soda, and probably other things I don't want to know about. We didn't drink the water, (we caught rain water) but a couple months later still could taste the diesel in the water. Initially we could feel the diesel on our skin or anything we washed. We paid locals to do laundry. When out in the boats, if we came across a clear stream, we'd wash there.

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What’s the matter? Diesel smell and taste good lol

L

I would attempt the repair in place.

No matter what you find epoxy and some thinking should work.

Greetings,
Mr. PM. I agree with the "repair it" posters. What's the worst that could happen? A water leak again? On the other hand, re-purposing the diesel contaminated tanks could present a whole batch of other problems as noted by Mr. L. I'm thinking here of absorbing residual hydrocarbons through the skin and/or leaving traces of same on dishes.

Fix it. Heck what else do you have to do with all your spare time?

You say the water tanks are built in, to me that implies fiberglass. Cut what ever access holes you need to replace the leaky fitting then patch the holes or install an access plate.

I don’t like aluminum water tanks and I would never put water In a tank that once held fuel even if I wasn’t going to drink it.

Indeed. Oil can affect rubber seals in heads etc.

Before making any decisions you need to find out what the tanks are made of and how the fittings are attached. Maybe they only need to be resealed.

If fiberglass then there is no reason the area cannot be repaired. I would use epoxy on a fiberglass tank. If the tank is frp and the attachment is poor or the area mount is thin it may simply need a patch built up to produce some real thickness and strength.

But first find out what they are made of and how the fittings attach.

Ok I finally dug into one of my tanks . They both have mushroom type thru hull plastic fittings. I’m positive this where they’re leaking. When I turned the flange nut it didn’t take much to break what little of a seal that was on the mushroom side inside the tank and crack fitting. I can’t reach the fitting through my inspection port so I’m going to use a coat hanger to fish out the fitting. I want to go back with something better. The tanks are fiberglass made to the boat and what I can see they look pretty good on the inside. The bottom of the tank is the hull. I left the starboard side in so you can see what I’m working with. If I can repair from outside it would be great . I’m looking for suggestions. Thanks

Marty, those look like cheap un-reinforced plastic fittings. They get brittle over time, but should last many years in that application.

I would replace them with reinforced plastic fittings like Tru Design sold in the US by Raritan.
http://raritaneng.com/product-category/trudesign/thru-hulls/

Banjo bulkhead fittings and hose barbs might be another way to go.

Bulkhead Fittings/Tank Accessories

Banjo Hose Barb Fittings

HopCar said:

Marty, those look like cheap un-reinforced plastic fittings. They get brittle over time, but should last many years in that application.

I would replace them with reinforced plastic fittings like Tru Design sold in the US by Raritan.
http://raritaneng.com/product-category/trudesign/thru-hulls/

Banjo bulkhead fittings and hose barbs might be another way to go.

Bulkhead Fittings/Tank Accessories

Banjo Hose Barb Fittings

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Thanks Parks. I like the looks of those sst bulkhead type fittings . Do they have a gasket on each side? With it being sst I could tighten pretty good. I guess I could run a wire up thru the hole wth the fitting on it and pull it up against the inside of the tank and tight the outside flange nut .

Marty I think they just come with one gasket that would be on the inside of the tank.

Banjo makes a lot of useful stuff. I used their hose connectors to set up an emergency bilge pump system.
Banjo Blk PP

HopCar said:

Marty I think they just come with one gasket that would be on the inside of the tank.

Banjo makes a lot of useful stuff. I used their hose connectors to set up an emergency bilge pump system.
Banjo Blk PP

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I think they will work if I have enough room for the diameter of the nut to sit flush against the tank. The hole is pretty close to the bottom of tank next to the hull.

If it won’t fit, you could patch the existing hole and drill a new one that would clear the hull. Or just grind a hole in the hull to get clearance...

I picked this bulkhead fitting up locally today just to see if I have enough room between the exit hole and hull for flange nut . The flange nut is left hand threads and there is a 1/2” female pipe in center and gasket for inside the tank .

Pack Mule said:

I picked this bulkhead fitting up locally today just to see if I have enough room between the exit hole and hull for flange nut . The flange nut is left hand threads and there is a 1/2” female pipe in center and gasket for inside the tank .

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Looks perfect. I suspect if you had a mushroom head thru-hull there previously, this ahould fit.

You could of course simply plug the hole and make a top opening to pull the water out.

I would not be too enthused about replacing the bulkhead fitting with another, the 1st go-round should be enough to dissuade you from that approach. I like the top access approach. Perhaps glass a companion flange into the top of the tank to create a top fitting that could be serviceable, but probably a bit of work. I'd be more inclined to create a threaded fitting or a composite nipple that could be glassed or epoxied into the tank.
I made a threaded flange by wrapping wetted glass tape around a dowel to build up enough wall thickness adequate for tapping with a standard NPT pipe tap. You could create such a fitting and epoxy it into the tank, then you'd have a tapped opening that you could eliminate any sort of gasket or mechanical joint inside the tank. I'd propose that no matter how robust the mushroom or bulkhead fitting, if it has a gasket, it's a source of future maintenance. Add to that the angle at the bottom of the tank, a solution that's epoxied into the tank would be a more durable option. A downside might be the potential for damage from over-cranking a male fitting into the fabricated flange. Not much water pressure on that joint, it wouldn't need to be drawn into next week, so unless you're really ham-fisted with it, shouldn't be an issue.

I have never quite understood why they put fittings on the side of any tank. Even as close to the bottom as you can get it. it still leaves a quantity of liquid in the tank.
Plus a hole under the level of liquid...

I guess for reasons of space or cheaper...

"I have never quite understood why they put fittings on the side of any tank. Even as close to the bottom as you can get it. it still leaves a quantity of liquid in the tank. ."

Some town water is rotten when taken aboard , tastes and smells like a swimming pool.

A drain in the tank bottom , just pull the hose, allows rapid removal .

Many folks will look at and taste the water before allowing any on board except for exterior washing.

Some town water is rotten when taken aboard , tastes and smells like a swimming pool.

We always bring 3 gallons of 'home' water with us to the boat for drinking !!


Do you drain to the bilge and then pump out or just pump the tank.... I'd rather have all the openings on top with a long pick up tube to the bottom. Until I can build a boat I'll just have to use what's already there.....

I removed the old fitting from the tank today. The caulking was still wet and almost felt like plumbers putty. It wasn’t stuck to fitting very well and not stuck very good to inside of the tank. The tank is fiberglass on both sides with 1/2 plywood in the center.

The plywood was gone about 3/8” around hole so there is a void. I dug out a blob of caulk that was in the void and cleaned it out with acetone. There is nothing that I like about this hole at all.I have canned my idea about a bulkhead fitting and now thinking about plugging this hole and drawing from the top with a tube as others have suggested.

What is the best way to plug this hole? It will have to be done from the outside. I also want to get the void filled. Should I just stuff thickened epoxy in the void then plug the hole somehow?

Are you able to fit an inspection port to the top of the tank? That will improve your access.

D.Duck44 said:

Are you able to fit an inspection port to the top of the tank? That will improve your access.

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There is an inspection port there now.im installing a new 6” port. I still can’t reach the hole in the bottom of the tank though . I’m not sure what material I should use for the draw tube , copper ?

Pack Mule said:

There is an inspection port there now.im installing a new 6” port. I still can’t reach the hole in the bottom of the tank though . I’m not sure what material I should use for the draw tube , copper ?

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PEX for the pickup.


RE the hole, try to get clean glass to start with. Ideally you'd want to do the patch from the inside to insure a leak proof job, but if that's not possible, you should be able to maybe overcut the outside so you have access to the back side of the inner wall/repair. Grind it to good glass, then wet it (with resin) and apply some wetted mat so there's a leakproof bond at least 3/4" beyond the margin of the inside hole. I'd use epoxy, it should give you better chance of it being waterproof. If you get glass tape the right width, it'll make it easier to work since it won't unravel as you work it onto the surface.

Maybe create a hard patch by wetting out some mat on a piece of wax paper and letting it cure, trim it to suit, then place it over the hole with thickened epoxy. If wall strength is an issue, you may want to add a piece of coring then replace or re-glass the outside skin.

Opening the outside may seem like more work, but in the end it'll probably take you less time if you open it up so you can work and make sure you get a good repair vs. doing it over. Patience!

Maerin said:

PEX for the pickup.


RE the hole, try to get clean glass to start with. Ideally you'd want to do the patch from the inside to insure a leak proof job, but if that's not possible, you should be able to maybe overcut the outside so you have access to the back side of the inner wall/repair. Grind it to good glass, then wet it (with resin) and apply some wetted mat so there's a leakproof bond at least 3/4" beyond the margin of the inside hole. I'd use epoxy, it should give you better chance of it being waterproof. If you get glass tape the right width, it'll make it easier to work since it won't unravel as you work it onto the surface.

Maybe create a hard patch by wetting out some mat on a piece of wax paper and letting it cure, trim it to suit, then place it over the hole with thickened epoxy. If wall strength is an issue, you may want to add a piece of coring then replace or re-glass the outside skin.

Opening the outside may seem like more work, but in the end it'll probably take you less time if you open it up so you can work and make sure you get a good repair vs. doing it over. Patience!

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Thanks, sounds like a good plan but how I can I grind the the inside of the tank for the patch?