Repair of stainless steel water tank

[brianlara 3]

Epoxy resin bonds to abraded 316/304 beautifully.
But in any case, being a simple job I'd be giving it a go and given you track record of success with such endeavours I reckon you'd pull it off too.
The alternative is an horrendous job. Got to be worth trying imho.

[captmikecoin]

Thank you everyone for your advice. It looks like I am going to have to take some of the woodwork apart to get a look at the lower edge of the tank. At that point I think I shall only be able to see one side of the tank and perhaps a little of the bottom face which slopes to follow the side of the boat. I hope then I will be able to see where it's leaking.

Brian, are you suggesting resin and glass on the inside or the outside of the tank? I'm not sure without being at the boat which would have easier access.

Cheers to all,

Mike

[brianlara 3]

Originally Posted by captmikecoin

Thank you everyone for your advice. It looks like I am going to have to take some of the woodwork apart to get a look at the lower edge of the tank. At that point I think I shall only be able to see one side of the tank and perhaps a little of the bottom face which slopes to follow the side of the boat. I hope then I will be able to see where it's leaking.

Brian, are you suggesting resin and glass on the inside or the outside of the tank? I'm not sure without being at the boat which would have easier access.

Cheers to all,

Mike

Thanks for asking Mike.
Presumably there is no access to the interior of the tank so only the outside can be laid up.
Cleanliness of the surfaces is paramount so a supply of (the highly flammable) acetone is required because the area will require a few cleanings.
Because the tank material is so hard the surface needs to be abraded/ roughened with (ideally) a 4 or 5 inch grinder fitted with a multi faceted flat flapper disc .
Every part of the metal which is to be glassed must be roughened. If not accessable with a grinder then sand the metal by hand but the rougher the better because adequate keying is important.
But prior to glassing I would but a two part epoxy putty, comes in a 1" app clear plastic tube about 6 or 7 inches long. Loctite is probably a brand available to you.
After cleaning and drying, even though the seam may be weeping, the required amount of putty is cut off and kneaded into a uniform colour.
The the thumb is used to force the miged putty into anything the could be an oriface. This stuff often kicks within 5 or 10 minutes so have everything ready.
After forcing the putty ensure that none is left in the surface of the metal...no superflous lumps, scraping the surplus of before it hardens.
But before you use the putty do the sanding first otherwise the vibration of the grinder may unseal the putty. After sanding wipe very clean with acetone.
Give the putty at least a few hours to fully harden prior to glassing.
Not having seen the tank I'm flying blind but I think that a glass width of 4 inches at least either side of the fracture sounds about right. Don't try to save money on materials.
The ideal glass would be woven rovings and given the importance of the procedure probably two or three layers of epoxy/matt sounds about right.
It shouldn't be necessary for the various layers of resin to have gelled/kicked prior to applying the subsequent layers of glass.
Both the epoxy putty and epoxy resin are non toxic once cured.
The epoxy putty I am takling about is oftern successfully used on hot, oily transmission cases because the tough putty is forced into the crack and despite hot transmission oil bieng present leaks are always halted.
Your water leak should be a walk in the park.
Good luck, take your time and always ask because there is plenty at stake.
Note above the job Jim successfully completed which still today is probably perfect.
Cheers Brian.

[capngeo]

Originally Posted by brianlara 3

Jim, because tig operates are much highet temps than mig, tig is the only thing which has the melting penetration required for thicker metals, say, 1/8 plate or thicker and forged or cast metals.
But for , say 20 or 18 gauge SS mig with the appropriate Argo-shield is best.
An analogy....if you tried to replace motor vehicle rusted area using tig it would be impossible...the parent metal would be blasted to smitherines.
But with mig which uses very low voltage, the finest work is possible not at all unlike stitching a piece of fabric. In fact with mig, "stitching" is proper terminology. 24 gauge welding of simple mild steel or stainless is a snack with mig but impossible with tig (well, impossible for me).
Done thousands of metres, literally.
This post intended purely as educational for those interested.
Cheers Jim

A good TIG welder can get down to <3 amps.... I have personally seen beer cans welded together, and have been told of guys welding foil with a TIG. Granted aluminum is AC welding where stainless is DC, but even I can weld 20Ga stainless with a TIG with almost no special effort.

To the OP: if a large access cover can be found or made, I would epoxy the inside of the tank instead of trying to remove and repair the entire tank.

[Seadoc777]

Originally Posted by zeehag

my 40 yr old stainless watertanks developed a leak or 30 +.. had them re welded, but the welder tig welded instead of mig welding and it again leaks. they only require rewelding to work again
you may wish to consult the welder face to face for this issue--
i wish one of the previous owners of this boat had left the original tank inside and used bladders so i could salvage that..hahahaha. i will be converting one water tank to fuel, after reconditioning tanks here in mazatlan. the only manufacturing of tanks i am needing is my fuel tank from hell.
the cost difference--
newly built 450 liter tank (fuel) mazatlan--450 usd. custom tankage.(14000 pesos)
rewelding old tanks--in colimilla, colima, mx-- 200 pesos at 16 pesos to 1 usd.

The man said it was just about impossible to remove the tank for repair and wanted any possible way to accomplish an inplace repair. I have a similar problem caused by excessive sloshing fore and aft. The slosh was cured by the introduction of baffle balls however the tank leak required removal of the tank and once located the leak was remedied with apoxy. The multiple discussions of welding were less than useless to the plea for help in the original message!

[Cheechako]

Originally Posted by brianlara 3

Jim, because tig operates are much highet temps than mig, tig is the only thing which has the melting penetration required for thicker metals, say, 1/8 plate or thicker and forged or cast metals.
But for , say 20 or 18 gauge SS mig with the appropriate Argo-shield is best.
An analogy....if you tried to replace motor vehicle rusted area using tig it would be impossible...the parent metal would be blasted to smitherines.
But with mig which uses very low voltage, the finest work is possible not at all unlike stitching a piece of fabric. In fact with mig, "stitching" is proper terminology. 24 gauge welding of simple mild steel or stainless is a snack with mig but impossible with tig (well, impossible for me).
Done thousands of metres, literally.
This post intended purely as educational for those interested.
Cheers Jim

Tig is preferred by far in the thinner stuff. I'm a former Aerospace engineer/welding engineer as well as previously a certified welder. It's all about the operator not the process. MIG may be ok with tanks on the thicker side.

[rosatte]

you guys might wanna reread his post looking for something to put in water to plug tank ...like pepper or the whites of a boiled egg....

[Cheechako]

Originally Posted by rosatte

you guys might wanna reread his post looking for something to put in water to plug tank ...like pepper or the whites of a boiled egg....

Yeah. Hey OP: Could you cut the top off the tank and put a plastic tank or two inside it?

[msrcal36]

I stopped pinhole leaks in my 40 year old Cal ss water tank. Luckily the inspection cover gave me access to the area inside. I roughed up the ss using 60 grit sand paper inside and outside. Then applied cloth and West Systems epoxy to both inside and outside. I used cloth that covered the area and extended about 3 inches past the effected area. It has worked great for 10 years.
Cheers
Mike

[Dody]

Friends of mine were facing the same problem. They decided to cut their whole interior out and re-build afterwards. Once they were able to move the tank up enough for access for welding, they discovered tiny holes in several places. For some reason they couldn't be convinced that it would be cheaper and faster to build a new tank instead of repairing the old one.
Welding done (TIG) they filled the tank with compressed air to check for leaks overnight. More leaks were found. Same procedure. It went on and on. After the 3rd set the guy doing the welding just left his gear on the boat ready for the next set of holes. After 3 1/2 weeks with a welding-session every day including sundays, living without a cabin-floor, crawling around the tank to get in or out of the boat, the tank held the air for 48 hours - only to develop or show another leak. This happened 2 more times and then the tank actually held the pressure for a week. Decision was made to stop here, get the tank in place and re-build the interior.

Well, the good thing is that the new interior is removable now without destroying the boat again should the tank be leaking next time. And next time, they decided, they will replace the whole tank, no matter how small the leak is.

Fair winds
Dody

[bongo]

I would make sure it is really the tank that is leaking. On our boat we thought we had a leaking tank because every time we would add water to the tank the floor adjacent to the aft inboard corner would get wet. So, I kept that tank MT for months, and the floor stayed dry for months. I needed to work in the bilge well and put the bilge pump in manual to pump out the well as low as it could go. Well, the floor got wet in the same place again. Turns out the PO had spliced the bilge pump overboard hose together with a piece of smaller diameter hose, hose clamps, and some press-seal, (not exactly a proper hose barb). This "repair" was hidden just under the aft end of the tank. I replaced the hose, and filled the tank with water. Turns out the tank was fine!

[captmikecoin]

Again, thanks to those who have posted ideas for the repair. Further investigation will be necessary when I get back to the boat in April so for now I am amassing ideas, tools etc to attack the job.

First of all I am planning to remove the bulkhead within the bilge, behind which the tank lurks. (The bilge below the saloon floor is about a metre deep and maybe slightly less wide). Then examine what I can see of the tank, maybe with the aid of one of those endoscopic tv cameras, with the intention of finding the source of the leak. At the same time I'll check that it really is the tank that's leaking but I think there is little doubt about that as it only happens after I've refilled the tank.

Depending on what I find I may effect the repair from the inside if I can get the baffles out easily or from the outside if accessible, most probably by the epoxy and glass mat method described earlier by Brian. But anyway we'll see when I start dismantling. As I said in my original post, I really don't want to be removing the tank. If that becomes necessary I'll leave it well alone and live with the leak which only amounts to about 100 litres out of a total of nearly 600 before it stops. The other similar tank seems OK just now.

Cheers,
Mike

[Oceanride007]

Having just had a similar experience with a 200lt SS tk. Thought I would this to the mix. In my case, with a steel hull, I had no choice but to take it out of a very difficult location to repair possible hull damage. Mine was Beam to Beam under refrig compressors one end and sea berth the other and under a very well built timber sole with poor access.
Well, I cut it out from the inside using long arms a combination of saber and angle grinder, strips had to be cut. Timber sole back in place now, I'm sailing without the tankage for time being. This is worse case scenario, but possible.
You won't see the leak with a scope, but if you reckon you cut a access hole over the area, patch with above mentioned products, from inside is the way to go, and make good your access hole.

[zeehag]

btw j-b weld does beautifully when you have the leak source identified.

[billgewater]

For what it's worth, my own tub was built starting 1972 and launched 1977. I had no money and still don't. So I had to be very careful with money. As a consequence I had three water tanks with a total capacity of about 2000 L (about 530 US gallons) all made by a local plumber who made farm tanks in galvanized sheet metal. The tanks all have baffles and outlets on all four bottom sides and same on top. Metal securing tabs were also soldered onto the bottom edges and vertical edges. This was to allow for any furniture/mounting arrangements. The builder folded all the edges and soldered them. The outside surfaces have been painted with epoxy coal tar to prevent external corrosion. 38 years later and all is still OK. No leaks. Yet ..... Being a born worrier I have made the furniture around these tanks removable ..... just in case. It's like it never rains if you carry an umbrella.

I have seen heaps of tank failures made in SS and aluminium (we spell it proper like). With these metals, alloying, tempering, fatigue cracking, surface properties, special welding techniques etc. are all areas where problems may arise. Just as well they look good, because they are invariably very expensive.