Repairs to Holding Tanks ?

[Jolly Roger]

Does anyone have any experience of repairing aluminum holding tanks? I knew mine had some corroded holes, so I cut a large inspection hole over the weekend and it was bone dry, probably not been used for many years. It has a number of corroded holes, the biggest about 2” x 1”. It will be very very difficult to remove and replace, so I wondered if there was a way to seal it from the inside, maybe using glass fibre and resin. I could cut a large hole in the top to give access to the inside, which is about a 24” deep vee shape to the hull shape. I was wondering if it could be spayed or something.

[boatman61]

Save a lot of work and $'s, shove a plastic collapsing water tank of the V type in there and connect the hose's.....

[rebel heart]

Not to be unhelpful, but what I did: Trash the whole thing and installed a composting head.

[atoll]

cut the top off and use it as a mould for a glass tank, alloy very difficult to repair once corroded,or do as boat man says

[thinwater]

Aluminum is a terrible material for holding tanks. Too bad.

I would follow Atoll's line of reasoning. At least 3 layers of glass cloth, but more would be better. A lid could be made from plywood and FRP.

[Jolly Roger]

Thanks for these suggestions:
I don’t think it’s practical to fit a bag inside the tank because it has a central divider/strengthener which is not corroded, and I don’t want to change out my new toilets. I think it would be possible to get enough access to glassfibre the inside, especially if the resin could be sprayed in. I did have another thought. What about expandable foam injected into the holes? Is that stuff resilient to you know what? It wouldn’t matter what it looked like.

[atoll]

apart from welding up the holes nothing is going to seal against alloy,epoxy putty after a thorough clean will work temporarly.
though on a critical installation like a holding tank where you dont want any leaks at all,best to scrap it,or use it as the mould for the new tank,even glassing it has its risks, sealing pipe inlets/outlets.
also if you do it in situ would reccomend using epoxy resin glass mix rather than polyester resin.

[gettinthere]

If you cannot replace the tank completely, cut out the top & the central divider and use the sides to contain a bladder. aluminum is not a good material for holding tanks

[atoll]

would agrree with gettin there this would be the most simple,effective solution,and probably cost effective as well

[DeepFrz]

I have not used a bladder but have heard bad new stories about them. I personally wouldn't use them for a holding tank. Spray in foam will not work. It will absorb the crap and stink your boat up. Replace the tank, unless you like cleaning poop out of the bilge. Sewage is very corrosive stuff so I would suggest if you are going to build your own tank (not recommended) you use fiberglass and epoxy. No spraying and don't try patching the aluminum tank.

[Jolly Roger]

Oh! Hecky thump! Thanks for all your replies chaps. I suspected it was going to have to be a new polyethylene tank slotted in somewhere nearby, then the old tank cut out when I feel up to it. It's an old Down Easter, 1977 so I expect plastic tanks were'nt available then. So who supplies the best tanks with the most shapes?

[gettinthere]

ronco plastics

[zeehag]

mine is plastic. is good for loong time unless sunburned-- but sun will never see inside my bilges...uhoh i sed never.....oops

[hanschristian38]

Triple M Plastics in kenebunk, Maine just made me a new tank to replace my SS tank. They will make any shape you need at a very reasonable price. Great service.

I made a diagram of what I wanted and the new tank is perfect.

[sck5]

the guy in the slip next to me when I got to Tortola last month had a holding tank blow up on the passage from Chesapeake Bay. You REALLY REALLY dont want this to happen to you because you wanted to save a few bucks and fix an old holding tank instead of getting a proper new one. His boat was uninhabitable for almost a week while he almost completely took apart the insides so that he could clean every single inch of the bilges. He would have paid a lot of money - more than a new holding tank could possibly cost - not to have that problem.