Leaking S/S water tanks

[Chris_Robb]

Boat: Westerly Oceanlord.

My port water tank is leaking, only when the boat is healed on starboard tack. I have not yet worked out where it is coming from, but assume that it is the top outboard seam, which is welded at a fairly acute angle. A large amount of water went into the bilge on a rare (for the med) hours sail.

The tanks look (relatively) easy to come out.

2 methods of repair might be suitable:
a) reweld seams on tank. (is this possible, as crevice corrosion in the welds may well be the culprit? Also in Greek boatyard.......)

b) Seal with epoxy paste (use glass tape and west system? or is there a form of epoxy tape somewhat like butyl tape for sealing portlights?)

To find the major leak may well be easy, but it would be useful to pressure test the tank in some way - I could use the electric dinghy pump pressurising through the inlet/ outlet pipe and spray with soapy water to see the bubbles from small holes)

Any ideas gratefully received.

 

[Tranona]

Had similar leak in the forward tank of my boat which only became apparent when it was full and motoring into head seas. Took it out (with great difficulty as it was foamed in!) and the source of the leak was obvious from staining around the weld but not really visible to the naked eye. The welder added a plate over the whole area so effectively doubling the seam. Did not cost much - the whole job including welding some new brackets on and adding an inspection hatch cost £150. Incidentally the tank was made in Greece as a replacement for the original Bavaria plastic tank and all the rest of the welding was sound.

 

[Chris_Robb]

Had similar leak in the forward tank of my boat which only became apparent when it was full and motoring into head seas. Took it out (with great difficulty as it was foamed in!) and the source of the leak was obvious from staining around the weld but not really visible to the naked eye. The welder added a plate over the whole area so effectively doubling the seam. Did not cost much - the whole job including welding some new brackets on and adding an inspection hatch cost £150. Incidentally the tank was made in Greece as a replacement for the original Bavaria plastic tank and all the rest of the welding was sound.

Thanks. I was hoping that someone had used an epoxy and I could be independant of the yard for repairs. Might as well have both tanks out whilst I am about it as there is a small weep in the stb tank too - but may just be filler pipe which I cannot get to - needing tightening up.

I am planning to go back in early December to do a weeks works - as I find it impossible to do maintenance when you have guests on board -= certainly not of this type!!!

 

[vyv_cox]

Chris, we discussed it when we met. I would have no concerns about using epoxy with woven tape. I have never used the technique for exactly this purpose but I have used it many times, including repairing a steel petrol tank and attaching the thrust plate for my Aquadrive. Adhesion should be fine if you abrade the tank thoroughly. The great thing about epoxy is that it does not shrink on cure, so joints will normally remain exactly as you laid them up. The beauty is that if for some reason it doesn't work you have lost nothing and could have it welded later.

 

[Chris_Robb]

Chris, we discussed it when we met. I would have no concerns about using epoxy with woven tape. I have never used the technique for exactly this purpose but I have used it many times, including repairing a steel petrol tank and attaching the thrust plate for my Aquadrive. Adhesion should be fine if you abrade the tank thoroughly. The great thing about epoxy is that it does not shrink on cure, so joints will normally remain exactly as you laid them up. The beauty is that if for some reason it doesn't work you have lost nothing and could have it welded later.

Hi Vyv - Your solution seems to be very workable - Not having much experience of West Epoxy - my only was when re gluing my cockpit gratings - when I mixed up too large a quantity and the whole pot went up in smoke in very short order!!! I did get it right on the second time - small quantities only....

I was also thinking that tape plus 1 coat of very runny stuff might not infact provide a perfect finish, with pinpricks allowing seepage. So 2 coats on the tape would be sensible?

 

[usernamenotvalid]

Perhaps no good in this case as the leak sounds quite substantial however a few small pinholes can fixed without a welder. A BLUNT centrepunch placed about three mm or so away from the leak (use a magnifying glass to identify exact location) Give it a good smack and it will throw up a small crater the edge of which should close the adjacent pinholes. Direct the punch towards the hole, not on it. I've used this on oil tanks when I couldn't be arsed dragging a welder over and setting it up. Will cost you nothing and it might work if a tank is weeping rather than leaking.

 

[Chris_Robb]

Perhaps no good in this case as the leak sounds quite substantial however a few small pinholes can fixed without a welder. A BLUNT centrepunch placed about three mm or so away from the leak (use a magnifying glass to identify exact location) Give it a good smack and it will throw up a small crater the edge of which should close the adjacent pinholes. Direct the punch towards the hole, not on it. I've used this on oil tanks when I couldn't be arsed dragging a welder over and setting it up. Will cost you nothing and it might work if a tank is weeping rather than leaking.

Sounds an interesting method. I would imagine that I have one major leak and probably several weeps where this might be suitable - but I don't want to have to do it again - so probably use the epoxy and cover all the welded seams.

Will be a messy job!

 

[ean_p]

Look at a product called 'Stop it' Its a purpose made epoxy tape mix that is used for pipe and vessel repairs. Will work even when the surface is wet and is quite impressive in operation! They make small size packs too!

https://www.youtube.com/watch?v=DmTrGl8lEZE

 

[Chris_Robb]

Look at a product called 'Stop it' Its a purpose made epoxy tape mix that is used for pipe and vessel repairs. Will work even when the surface is wet and is quite impressive in operation! They make small size packs too!

https://www.youtube.com/watch?v=DmTrGl8lEZE

A polyurethane glue which uses water in it chemical reaction - great stuff, but I am not sure how it would be used on a flat surface.

Having used it in its glue gun form, It does produce one hell of a lot of expanding foam. I have a small pipe repair to do at home, so I might try some on a flat surface as a trial.