Repair of stainless steel water tank

[captmikecoin]

I have a leak in one of the stainless water tanks on my Liberty 49 which is some 27 years old. Although I know that the proper solution is to re-weld what I suspect is a leaking seam or perhaps to replace the tank, removal of the tank is well nigh impossible as it's under the saloon floor (remove saloon seating and floor under the seating, remove fixed part of the teak floor, generator and its platform, cut out a bulkhead, and possibly remove the keel stepped mast)! Then would come the problem of sourcing a good quality custom made tank in Greece.

So, is there any kind of "leak stopper" I can put in the tank? I have in mind some kind of liquid to add to the water. Or any other ideas? I have access to about 1/4 of the top of the tank where the inspection cover is located.

Otherwise I'm just going to have to live with it which is not an impossibility as it stops leaking once the level is down to about 2/3 full. However it will probably only get worse.

Mike
S.Y. Carpathia

[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.

[SailRedemption]

I fixed the leaks in two of our three tanks with JB Weld Waterweld epoxy. The third tank was epoxied twice on the corner plate welds but still failed. We cut it out and will replace. The other two are holding.. For now.

If it's just a small leak, try it but if the welds are crappy like ours were it may or may not work. Also, after you do it, baby your tanks and don't fill them up to 100 percent.

[charliehows]

just pulled my stbd water tank out - been putting it off for 5-6 years (thought it was going to be a much harder job than it turned out to be). Turns out what i thought was a probable weld failure was actually just perished hosing. Like your tank, mine is in the 25-30 year old range, but having had a chance to thoroughly inspect it, it's in absolutely perfect condition inside and out. It's now back in place with a couple of modifications to the surrounding joinery to allow easy access to the hosing, and functioning well. My experience may be of no use to you at all - you seem quite sure that a; the tank has a breach, b; it's extremely hard to remove, and c; its still usable within limits.

[leftbrainstuff]

Originally Posted by captmikecoin

I have a leak in one of the stainless water tanks on my Liberty 49 which is some 27 years old. Although I know that the proper solution is to re-weld what I suspect is a leaking seam or perhaps to replace the tank, removal of the tank is well nigh impossible as it's under the saloon floor (remove saloon seating and floor under the seating, remove fixed part of the teak floor, generator and its platform, cut out a bulkhead, and possibly remove the keel stepped mast)! Then would come the problem of sourcing a good quality custom made tank in Greece.

So, is there any kind of "leak stopper" I can put in the tank? I have in mind some kind of liquid to add to the water. Or any other ideas? I have access to about 1/4 of the top of the tank where the inspection cover is located.

Otherwise I'm just going to have to live with it which is not an impossibility as it stops leaking once the level is down to about 2/3 full. However it will probably only get worse.

Mike
S.Y. Carpathia

The choice is either remove and replace all with plastic or repair.

Step one is to remove any sludge and let the remaing stainless reform the oxide. Then you can repair with epoxy. Either by building an epoxy liner or spot repairing.

If you spot repair, you'll need to get the stainless bright under the repair. Otherwise it will likely suffer crevice corrosion. Not such an issue in fresh water.

If its only a few repairs spot repairs work well. Otherwise plan to epoxy line the whole tank. This process is common for corrosive environments. There are lots of specialists epoxies and vinyl esters.

The challenge is access, removing the baffles and getting a uniform finish.

You could even try a self tapper coated with potable water sealant screwed into the leak. It's crude but will often seal a pin hole. You'll likely break the fastener off into a weld.

We have a Liberty 458. I've cleaned all our tanks and inspected the interiors. Crap mig welds. Not tig welded so I'm surprised they've lasted 33 years. There was only a light film of sludge from the po so they're in good condition.

We did have a leak in one. Found the pipe thread bung was sitting in an oversized female thread welded in the base of the tank. I turned up an oversize tapered thread bung and refitted it with potable water thread sealant. No leaks for 2 years.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[Jim Cate]

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

....

Zee, I'm wondering why you say this about the welding? I'm not a pro welder, but have done a fair amount of s/s fabrication, and TIG is the method of choice IMO.

Jim

[Sailmonkey]

Originally Posted by Jim Cate

Zee, I'm wondering why you say this about the welding? I'm not a pro welder, but have done a fair amount of s/s fabrication, and TIG is the method of choice IMO.



Jim

+100

Mig does not a pretty stainless weld make

[brianlara 3]

Originally Posted by Jim Cate

Zee, I'm wondering why you say this about the welding? I'm not a pro welder, but have done a fair amount of s/s fabrication, and TIG is the method of choice IMO.

Jim

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

[Sailmonkey]

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

For my own benefit, when one is stitching a tank weld, how does one ensure no pinholes between stitches? I've seen really good tig welders weld some really thin stuff.....they all had water cooled torches and foot pedal voltage controls though.

[brianlara 3]

Originally Posted by Sailmonkey

For my own benefit, when one is stitching a tank weld, how does one ensure no pinholes between stitches? I've seen really good tig welders weld some really thin stuff.....they all had water cooled torches and foot pedal voltage controls though.

Good post SM.
I haven't used water cooled tig because I've never needed to, never even seen it.

About holes. There are no holes because in "'stitching' each blob of fusion metal overlaps the previous blob by usually 50% or better. Effectively it is a continuous run just as if it were gas welding, which is also often done as a stitch. Especially when welding 20# aluminium wheel arches for buses which are huge having 20 inch duals on the rear.
Never even seen a watercooled tig. In tourist coach construction only normal tig (not by me) , mig, oxy and stick were used by me.
Mig produces absolutely beautiful welds in light applications. That's why panel beaters use mig to (e.g.) fit new rear quarter panels to roofs. Almost no heat and so no distortion, sparks, flames and almost no grinding away of proud weld metal.
The above not withstanding I suspect (!!) thar the stainless fabrication seen on rec boats is tig'd.

[Jim Cate]

Brian, I see what you are saying about very light gage sheet metal. I'm not sure what Zee's tanks are made of, but at least one Taiwan boat I'm familiar with had tankage made up of 1/8 inch s/s, and I've TIGed such with good success. If the tanks in question are as thin as your example, I'd not bother repairing/welding... they are likely just going to continue to cause trouble post repair.

Jim

[a64pilot]

No, I used to be a Pro welder and work now building aircraft who's fuselages are 4130 steel tube.
TIG is superior in every respect to MIG, MIG is good for building cheap stuff fast, like bush hogs and other farm equipment.
But if quality is first and foremost above speed, TIG is the way to go, a good TIG welder can weld a beer can back together.
TIG is not for real thick stuff, can't get enough heat for that, if your building an oil rig, you use plain ole fashioned stick welding

[brianlara 3]

Originally Posted by Jim Cate

Brian, I see what you are saying about very light gage sheet metal. I'm not sure what Zee's tanks are made of, but at least one Taiwan boat I'm familiar with had tankage made up of 1/8 inch s/s, and I've TIGed such with good success. If the tanks in question are as thin as your example, I'd not bother repairing/welding... they are likely just going to continue to cause trouble post repair.

Jim

You've done more tig than me Jim. My only tig was at technical college.
Yep, only very small tanks, say 50 litres, could be mig'd.
It'possible that the leaks are merely welds which have opened up because of less than adaquate baffling.
Not having seen the tank in question, is it possible that some epoxy ribbon (non toxic once set) could be squeezed into the crack and then the seam glassed over with multiple layers of glass woven tape....eg lavers of 4" tape over lapping AFTER the entire erea is sanded (mechanically) perfectly and then wiped perfectly clean with acetone?
If it were my tank I'd be fixing it that way, because the alternative is a rebuild of the boat.
Assuming of course, the seams are accessable.

[brianlara 3]

Addendum....ONLY epoxy resin.
Polyester resin not a good thing at all.

[Jim Cate]

Dunno if it would work on s/s, and dunno if the leak is even accessible...

On our previous boat, I had a ~45 gallon aluminium diesel tank made up by a pro tank shop in California. Looked great, and actually fit into t he designated space in the boat. But, a couple of years down the track a weld, along a 90 degree corner of the tank, developed a small leak. No aluminium welders in the tuomotos, so I used some Marine-Tex epoxy bog and a neat patch cut from an aluminium beer can formed over the bog. It never leaked again, and that mickey mouse repair was still standing proud when we sold the boat 15 years later. For all I know,it is still working!

Jim