jenevers Posted June 8, 2019 Report Share Posted June 8, 2019 Had a leak, applied epoxy putty, put tank under air pressure, applied soapy water where leak had been, no bubbles ?. Put some water in and ....damp patch next morning?. I assumed that air is thinner than water so how come water gets through where air doesn't? Link to comment Share on other sites More sharing options...
cuthound Posted June 8, 2019 Report Share Posted June 8, 2019 8 minutes ago, jenevers said: Had a leak, applied epoxy putty, put tank under air pressure, applied soapy water where leak had been, no bubbles ?. Put some water in and ....damp patch next morning?. I assumed that air is thinner than water so how come water gets through where air doesn't? Could there have been two leaks in close proximity, only one of which was repaired? Link to comment Share on other sites More sharing options...
jenevers Posted June 8, 2019 Author Report Share Posted June 8, 2019 25 minutes ago, cuthound said: Could there have been two leaks in close proximity, only one of which was repaired? No the leak is where I patched and although there were no air bubbles under pressure there was a damp patch next morning. Weird. Link to comment Share on other sites More sharing options...
Bee Posted June 8, 2019 Report Share Posted June 8, 2019 Water has slowly worked its way through, repair has only worked for a short time. Link to comment Share on other sites More sharing options...
Neil2 Posted June 8, 2019 Report Share Posted June 8, 2019 I'm curious as to how you pressurised the tank? How big is it and what is it made out of? Link to comment Share on other sites More sharing options...
Murflynn Posted June 8, 2019 Report Share Posted June 8, 2019 I assume you have repaired the leak from the inside. I would remove the putty, clean the location really well, then apply some neat epoxy resin to act as a primer, and when it is touch dry apply some epoxy thickened with microfibres filler to 'peanut butter' viscosity, apply gentle heat until the filler is rock hard ........... job's a good'un. Link to comment Share on other sites More sharing options...
jenevers Posted June 8, 2019 Author Report Share Posted June 8, 2019 1 hour ago, Neil2 said: I'm curious as to how you pressurised the tank? How big is it and what is it made out of? Sealed the inlet and breather, disconnected the pipe after the on/off tap and blew it up. 700 litres, stainless steel. 1 hour ago, Murflynn said: I assume you have repaired the leak from the inside. I would remove the putty, clean the location really well, then apply some neat epoxy resin to act as a primer, and when it is touch dry apply some epoxy thickened with microfibres filler to 'peanut butter' viscosity, apply gentle heat until the filler is rock hard ........... job's a good'un. No, from the outside. Tank doesn’t have an access door. Link to comment Share on other sites More sharing options...
Murflynn Posted June 9, 2019 Report Share Posted June 9, 2019 (edited) Strange that a steel water tank doesn't have an access hatch. So you can never inspect it or scrub it clean. I wouldn't expect any external epoxy repair to be able to withstand water pressure. Needs welding IMHO. Edited June 9, 2019 by Murflynn Link to comment Share on other sites More sharing options...
Bee Posted June 9, 2019 Report Share Posted June 9, 2019 We have a plastic tank, its a window cleaners tank with a big access lid and after more than 10 years there is just a tiny bit of sand in it, never needed cleaning. We had a steel tank on a previous boat and after 4 years it had horrible sludge and crud in it. I would bin the steel tank especially as it is corroded anyway. Link to comment Share on other sites More sharing options...
Murflynn Posted June 9, 2019 Report Share Posted June 9, 2019 35 minutes ago, Bee said: We have a plastic tank, its a window cleaners tank with a big access lid and after more than 10 years there is just a tiny bit of sand in it, never needed cleaning. We had a steel tank on a previous boat and after 4 years it had horrible sludge and crud in it. I would bin the steel tank especially as it is corroded anyway. OP says it's stainless so more likely a weld seam defect. Link to comment Share on other sites More sharing options...
jenevers Posted June 9, 2019 Author Report Share Posted June 9, 2019 4 hours ago, Bee said: We have a plastic tank, its a window cleaners tank with a big access lid and after more than 10 years there is just a tiny bit of sand in it, never needed cleaning. We had a steel tank on a previous boat and after 4 years it had horrible sludge and crud in it. I would bin the steel tank especially as it is corroded anyway. Interesting. How big is it? Link to comment Share on other sites More sharing options...
Alan de Enfield Posted June 9, 2019 Report Share Posted June 9, 2019 (edited) 16 hours ago, jenevers said: Sealed the inlet and breather, disconnected the pipe after the on/off tap and blew it up That might explain why its no longer watertight !! Edited June 9, 2019 by Alan de Enfield 1 Link to comment Share on other sites More sharing options...
Guest Posted June 9, 2019 Report Share Posted June 9, 2019 5 hours ago, Murflynn said: OP says it's stainless so more likely a weld seam defect. Many years ago a fabricator told me that stainless steel needs to be pickled and passivated following welding. I have no idea if this is true or what it means. He did claim that welded stainless seams could give problems if not treated thus. Link to comment Share on other sites More sharing options...
jenevers Posted June 11, 2019 Author Report Share Posted June 11, 2019 (edited) I was surprised at the colour of the water that I drained from the tank when I totally emptied it. It was like tomato soup. Tank is about 15 years old. Looks like it's rusting which I've just confirmed on YouTube does happen even to stainless steel, if not passivated / pickled. Edited June 11, 2019 by jenevers Link to comment Share on other sites More sharing options...
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