Re-Welding Stainless Tanks?

[minaret]

High Performance - W9200 System Potable Water Coating

[Canibul]

I've been checking around. The local TIG/MIG stainless welding guys charge $100 per hour and I could see someone spending several hours per tank.

I can't really glass the outside of the tanks, they're already a tight fit. If I increase the outside dimensions, I'd never get them back in without also ripping up the flooring etc. I don't want to have to do that.

I'm interested in the idea of coating the inside of the tanks. They have large removable inspection hatches on the top. I can get to the insides. But I think the leak is around the large port that connects the tanks together. A 1.5" diameter stainless pipe welded to the end of the tank. These seem to be where they fail.

There are plastic 50 gallon tanks out there that will fit, for $ 216 each. Four of those would replace these four stainless tanks. That's certainly cheaper than hiring local welder.

[Aloha_float]

Welding engineering guy here...tig weld only
Suggest you get a shop to do it and pressure test the tanks
I know it's not the lowest cost solution up front...but the least aggravating
If you have no experience, you are likely going to cause more harm than good
Do not stick weld....that would just leave you with Swiss cheese joints


Sent from my iPad using Cruisers Sailing Forum

[Cheechako]

3 hours per tank seems a bit much... but hard to say I suppose. Depends on how much prep you are asking him to do.
So you have 4 tanks? are they all leaking? Maybe you should remove one and see what the real situation is? It's possible most of the welding is good but it was marginal in a few places. Those tanks must not be very big...? Your boat is only 36 right?
Remove one, assess the situation, repair it maybe with the tig welder and see what it costs. Maybe when the one is done, you can get him to bid the other three based on what he knows.

[model 10]

Originally Posted by Canibul

I've been checking around. The local TIG/MIG stainless welding guys charge $100 per hour and I could see someone spending several hours per tank.

I can't really glass the outside of the tanks, they're already a tight fit. If I increase the outside dimensions, I'd never get them back in without also ripping up the flooring etc. I don't want to have to do that.

I'm interested in the idea of coating the inside of the tanks. They have large removable inspection hatches on the top. I can get to the insides. But I think the leak is around the large port that connects the tanks together. A 1.5" diameter stainless pipe welded to the end of the tank. These seem to be where they fail.

There are plastic 50 gallon tanks out there that will fit, for $ 216 each. Four of those would replace these four stainless tanks. That's certainly cheaper than hiring local welder.

I have sloshed the insides of aluminum gas tanks several times. With the right stuff it works great for pin hole type leaks. With a big fitting flexing like you may have, I would not trust the stuff. I think you are pretty lucky to be able to fit plastic tanks.

[Canibul]

After looking at the options on fixing the stainless tank that's leaking and further inspection of the others, I'm leaning even harder toward pulling them all out and replacing them with plastic. I found two active leaks, both in th same hull. One was at the Shurflo pump fitting itself, and the other is somewhere on the aft end of the forward tank. I can't tell exactly, because the entire end of the tank is coated with what looks like straight epoxy. no mat or glass. Just yellowing, peeling, fading, semi-flexibly old expoxy. I am amost certain that the leak is in the weld around the pipe fitting.
For about a thousand bucks, I can have four brand new poly tanks with working level sensors installed, and fresh new hoses throughout. I'll be cleaning and painting bilges and going over everything I find during the process. This is a good thing on an old boat.

If I go the re-welding route, I'll always be waiting for the next weld to crack. Unless I get them all done and now we're talking more money than replacing them with plastic. And I'd always be dealing with 30 year old plumbing. Replacing them lock, stock and barrel means I'll know what I have, that the hose clamps are not rusty old perforated junk, etc.

My experiences with rehabbing a neglected old boat so far have been that once I get the old damaged stuff out, I find additional problems. I can already see that the welds that are not leaking are rusty stainless. I really don't want to have to deal with a hundred gallons of fresh water loose in the bilge. The plastic tanks are looking better. And I'm lucky to find a standard size that fits.

I could probably fit another fifty gallon tank in each hull, which would bring me to 300 gallons storage, but right now I'm thinking 200 is more than enough for two people.

[slowshoes]

Originally Posted by Canibul

After looking at the options on fixing the stainless tank that's leaking and further inspection of the others, I'm leaning even harder toward pulling them all out and replacing them with plastic. I found two active leaks, both in th same hull. One was at the Shurflo pump fitting itself, and the other is somewhere on the aft end of the forward tank. I can't tell exactly, because the entire end of the tank is coated with what looks like straight epoxy. no mat or glass. Just yellowing, peeling, fading, semi-flexibly old expoxy. I am amost certain that the leak is in the weld around the pipe fitting.
For about a thousand bucks, I can have four brand new poly tanks with working level sensors installed, and fresh new hoses throughout. I'll be cleaning and painting bilges and going over everything I find during the process. This is a good thing on an old boat.

If I go the re-welding route, I'll always be waiting for the next weld to crack. Unless I get them all done and now we're talking more money than replacing them with plastic. And I'd always be dealing with 30 year old plumbing. Replacing them lock, stock and barrel means I'll know what I have, that the hose clamps are not rusty old perforated junk, etc.

My experiences with rehabbing a neglected old boat so far have been that once I get the old damaged stuff out, I find additional problems. I can already see that the welds that are not leaking are rusty stainless. I really don't want to have to deal with a hundred gallons of fresh water loose in the bilge. The plastic tanks are looking better. And I'm lucky to find a standard size that fits.

I could probably fit another fifty gallon tank in each hull, which would bring me to 300 gallons storage, but right now I'm thinking 200 is more than enough for two people.

I know where your coming from regarding your comments on rehabing an older boat - mine is 29 years old. Your lucky you can pull your tanks with no major surgery needed to your boat to get them out.

I would have to do at least some minor surgery to my boat, and probably even partially cut up the tank, to get mine out. The new tank would also have to be smaller to enable me to get the new one back in, so I'd lose some capacity as well. All these factors are leading me to at least give the Microseal stuff a shot. I do have pretty good access to the inside of my tank.

[Terra Nova]

Replace with plastic tanks. Even if you pay a welder to try to repair your existing tanks, the same problem will likely occur, perhaps soon after re-installation.

Few welders will take the time to purge the inside of the tank with inert gas, while welding. This can cause "sugaring" and soon lead to failure.

[minaret]

Originally Posted by slowshoes

I know where your coming from regarding your comments on rehabing an older boat - mine is 29 years old. Your lucky you can pull your tanks with no major surgery needed to your boat to get them out.

I would have to do at least some minor surgery to my boat, and probably even partially cut up the tank, to get mine out. The new tank would also have to be smaller to enable me to get the new one back in, so I'd lose some capacity as well. All these factors are leading me to at least give the Microseal stuff a shot. I do have pretty good access to the inside of my tank.

How big is the tank? What is it for?

[slowshoes]

Originally Posted by minaret

How big is the tank? What is it for?

It's a 35 gallon freshwater tank. I have an identical tank to starboard and a third up forward. Only the port tank is leaking - minor leak, but I still want it fixed.

[minaret]

Originally Posted by slowshoes

It's a 35 gallon freshwater tank. I have an identical tank to starboard and a third up forward. Only the port tank is leaking - minor leak, but I still want it fixed.

For fresh water tanks that small, replacement with plastic tanks is probably the best option. But, if removal and replacement is truly a nightmare which will cost many hours of labor, I have fiberglassed and then coated the inside of a tank before. Basically you are using the existing tank as a mold to build a glass tank in place. This is a more long term solution than just coating, and it requires no removal. Just good access and a tank with not too strange a shape. Obviously for a water tank you must use a sealer approved for potable water over the glass. It's quite a bit more work than just sealer, but at least you know it won't fail in a couple of years.

[Cheechako]

My experiences with rehabbing a neglected old boat so far have been that once I get the old damaged stuff out, I find additional problems. I can already see that the welds that are not leaking are rusty stainless. I really don't want to have to deal with a hundred gallons of fresh water loose in the bilge. The plastic tanks are looking better. And I'm lucky to find a standard size that fits.
Yeah, I hear you, you are likely right, by the time they are out you will want new ones. I wouldn't over do the water storage/weight on a cat that small...

[slowshoes]

Originally Posted by minaret

For fresh water tanks that small, replacement with plastic tanks is probably the best option. But, if removal and replacement is truly a nightmare which will cost many hours of labor, I have fiberglassed and then coated the inside of a tank before. Basically you are using the existing tank as a mold to build a glass tank in place. This is a more long term solution than just coating, and it requires no removal. Just good access and a tank with not too strange a shape. Obviously for a water tank you must use a sealer approved for potable water over the glass. It's quite a bit more work than just sealer, but at least you know it won't fail in a couple of years.

Thanks for the reply minaret - the fiberglass solution hadn't occurred to me. It won't require major surgery to get the tank out, but I will for sure have to cut part of the tank up to get it out. I shouldn't have to do any cutting on any of the finish joinery if I cut the tank.

I'll probably at least try the Microseal - it's by far the most economical and easiest, although I'll say that I'm the type that likes to do things right, so cheapest and easiest isn't always the best solution for me. (my wife will tell you it never is!). Looks like I have some thinking to do. With two other functioning tanks, I at least don't feel like I need to rush to come up with a solution.

[Broken-Sailor]

Originally Posted by Canibul

After looking at the options on fixing the stainless tank that's leaking and further inspection of the others, I'm leaning even harder toward pulling them all out and replacing them with plastic. I found two active leaks, both in th same hull. One was at the Shurflo pump fitting itself, and the other is somewhere on the aft end of the forward tank. I can't tell exactly, because the entire end of the tank is coated with what looks like straight epoxy. no mat or glass. Just yellowing, peeling, fading, semi-flexibly old expoxy. I am amost certain that the leak is in the weld around the pipe fitting.
For about a thousand bucks, I can have four brand new poly tanks with working level sensors installed, and fresh new hoses throughout. I'll be cleaning and painting bilges and going over everything I find during the process. This is a good thing on an old boat.

If I go the re-welding route, I'll always be waiting for the next weld to crack. Unless I get them all done and now we're talking more money than replacing them with plastic. And I'd always be dealing with 30 year old plumbing. Replacing them lock, stock and barrel means I'll know what I have, that the hose clamps are not rusty old perforated junk, etc.

My experiences with rehabbing a neglected old boat so far have been that once I get the old damaged stuff out, I find additional problems. I can already see that the welds that are not leaking are rusty stainless. I really don't want to have to deal with a hundred gallons of fresh water loose in the bilge. The plastic tanks are looking better. And I'm lucky to find a standard size that fits.

I could probably fit another fifty gallon tank in each hull, which would bring me to 300 gallons storage, but right now I'm thinking 200 is more than enough for two people.

You might want to check if those plastic tanks are baffled or not too. I don't know about you but I would want something to slow the sloshing of all that water around. Having pulled non baffled 500 gallon water tanks around with a pickup, I know first hand what it will do to the vehicle hauling it around when you start, stop, or do any other fast movements. In rough water you don't want that water pushing your boat around too.

[Terra Nova]

The plastic tanks are not baffled.