Water tank removal/repair

[Caladh]

Our 245 litre S/S water tank is leaking - somewhere. It is 20 years old and has not been "used" in anger for at least 4 years. However as it is a good Scandanavian design, the tank has been epoxied and glassed in and effectively cannot be removed (well not without a great deal of work). I am thinking about cutting the top off it which would be accessible via the large stern locker and then fitting another tank inside the shell.

I am open to any other forumite suggestions !

 

[Norman_E]

Even if you get it out you will probably find that there are pinhole leaks at welds. If you weld them up it is only going to give you a bit more life before other pinholes develop. I had my removeable stainless tanks welded about two years ago. So far so good, but I will replace them with plastic ones when they leak again.

Your scheme looks good to me especially if you can get a decent plastic tank made to fit.

 

[Chris_Robb]

Even if you get it out you will probably find that there are pinhole leaks at welds. If you weld them up it is only going to give you a bit more life before other pinholes develop. I had my removeable stainless tanks welded about two years ago. So far so good, but I will replace them with plastic ones when they leak again.

Your scheme looks good to me especially if you can get a decent plastic tank made to fit.

I would agree that you may have hit on the best way. However if you can get at the the welded edges of the tank (especially where there is an acute angle on the outside) I repaired mine with epoxy and glass tape several years ago now with no re-occurring leaks. In my case the tanks came out easily. As others have said - its normally the crevice corrosion in the welds - bad welding?

 

[Caladh]

Even if you get it out you will probably find that there are pinhole leaks at welds. If you weld them up it is only going to give you a bit more life before other pinholes develop. I had my removeable stainless tanks welded about two years ago. So far so good, but I will replace them with plastic ones when they leak again.

Your scheme looks good to me especially if you can get a decent plastic tank made to fit.

Well one of the tanks has been removed and yes there are more pin holes in it than a dart board so I think we are going to have a new one made. In the meantime if Chris R responds can you tell me which tape and epoxy you used for your tank repair ? This for the tank which we cannot remove.

 

[Chris_Robb]

Well one of the tanks has been removed and yes there are more pin holes in it than a dart board so I think we are going to have a new one made. In the meantime if Chris R responds can you tell me which tape and epoxy you used for your tank repair ? This for the tank which we cannot remove.

The epoxy I used was the standard west system with glass tape plus filler to thicken the epoxy to a runny paste.

The tank I needed to do had a significant number of pinholes - the whole content of the tank leaked out on an 8 hour starboard 8 knot reech.

Process. Sand down the edges where you are going to tape with not to coarse a grit, which will help increase the mechanical bond. Do any other edges that are welded as it takes very little time. The worst were those weld at an acute angle (shaped to the hull under the saloon seats).

Then cut your lengths of tape - the tape is about 3 inches wide from memory - in advance otherwise you wont have enough tome to work if its hot!

Mix the epoxy in small quantities having regard for the temperature. Add in filler, microballons or what ever to make a runny paste.

Apply with small brush stippling to get full wetting (bet you know this already!) wet the seam to be doen with epoxy first they put on the tape and wet out. Allow to cure and apply further coat.

End of leaks - that was 3 years ago. Also a very cheap repair. Consider saving your old tank this way as it really works. I would NOT go for another stainless tank unless you know the capability of the welder as stainless is a bugger for pitting on the welds. Teck tanks however make a great product.

Other thoughts - think about the best way of fitting tanks gauges that actually work. I have heard that the air pressure type are very good.

Good luck.

Let us know where you are.

 

[rogerthebodger]

There is a produce local to me called Durapond. This is designed for the sealing of fish ponds and water tanks. It is a polyurethane based product.

http://www.duram.co.za/products/durapond-2/

The same company also supplies other polyurethane products that is very hard wearing and ic used to seal and protect the load box of pickup and trailers.

http://www.duram.co.za/products/durabak-2/

One of our local marinas used this product to seal the outside of expanded polystyrene floats for the floating jetties that we moor ove boats to and to provide walk on access to.

There is also a metal primer for stainless that can be used to provide a key to the metal

 

[Caladh]

Thanks Chris and Rogershaw for your inputs. Tek tanks are on the case.