Repairing a water tank: why wouldn't this work?

[Puggy]

Hello all,

I am wrestling with one of my two 350 litre stainless steel water tanks that is leaking. The tanks are under the floor on top of the keel under the cabins, and it would be hugely traumatic to extract them, and bloody expensive for the replacement custom Tec-tank - the quote is looking around £5000 for parts and labour for one tank...

So - the alternative would be to repair it. I have been looking on the YBW forums, and this topic does come up and there are some who claimed to have fixed tanks with some success. but I wanted to run an idea past everyone.

My thinking is broadly this:
- Cut a large access hole in the top of the tank, ideally the length of the tank.
- clean the tank, probably chemically, to provide a key surface. Dry thoroughly. This will be fiddly as the tank is baffled. Might need some form of abrasion to make the expoxy adhere which could be tricky...
- spray the inside of the tank with Altex Altra-shield 2000 epoxy which is certified for potable water (http://www.altexcoatings.co.nz/vdb/document/247). This will probably require some cleverness with a X100 thinned version of the epoxy applied via a pressurised paint spray compressor with a long lance on the end to get into the hard to reach spaces.
- fit a hatch to the top of the tank: get a hatch and flange arrangement made up in S/S and tap and screw it down with a suitable sealant. This cannot be impossible as tank manufacturers fit hatches all the time.

The issues I can see.
- the baffles could be so obstructive that it is impossible to reach all the areas.
- the epoxy won't stick without some form of physical abrasion to provide a key
- the structural integrity of the tank is so compromised by cutting the lid open that the tank becomes unstable or impossible to properly seal.

I am sure these are all solveable.

What is the worst that can happen? It leaks! And the best? Well, it doesn't, the boat isn't pulled apart, and costs much less money.

What do people think about the viability of this?

Thanks. Puggy

 

[Buck Turgidson]

Why not remove the baffles and use the space to hold 3 interconnected flexi bag tanks?

 

[lw395]

Do you know where or why it is leaking?
If it is at a fitting, I would suspect the epoxy would crack at the same point after time.
If it is whatever the tank is sat on, wearing through, likewise.

If it is a corroded weld then the epoxy might be in with a chance.
No reason why a hatch cannot be made to work. May need to reinforce around the inside of the aperture to keep it flat, and fit a suitable gasket?

 

[Talulah]

We replaced our water tank just before Christmas. Cost was significantly less than your figure of £5k.
Similar sized tank to yours located under the floor above the keel.
Custom TecTank was about £1600. Labour was DIY. Additional costs were pretty nominal.
Thread on the subject here: http://www.ybw.com/forums/showthread.php?379023-Replacing-Water-Tank&highlight=

 

[ean_p]

errrrr just have it welded up!

 

[KellysEye]

Assuming the tank has an access point then get it professionally cleaned they pump out the diesel through filters then they normally steam pressure wash the tank, then dry it. Then find the leak and get it welded, not all welders can weld SS so find one who can. Then put the clean diesel back.

 

[Tranona]

Assuming the tank has an access point then get it professionally cleaned they pump out the diesel through filters then they normally steam pressure wash the tank, then dry it. Then find the leak and get it welded, not all welders can weld SS so find one who can. Then put the clean diesel back.

Not sure what good that will do when the OP is having problems with his WATER tank. Might do more harm than good.

 

[Vara]

Do you have total access to the top of the tank?

If yes, chop off top of tank and remove baffles replace with tek tank inside, will give reduced capacity but should be watertight.

 

[RobbieW]

My experience of this, with a similar sounding installation, was that once the tanks were out I could see that they had suffered crevice corrosion all over the base and up about an inch. I strongly suspect that this was a result of standing in a little bilge water almost permanently. They werent easy to extract but could have been much harder if the joinery under the cabin sole hadnt had joints in all the right places to unscrew and lift out sections of woodwork (ok, a hammer was involved but the only repair needed was after I trod on a vulnerable piece I shouldnt have). Once the wood was out of the way the tanks lifted out cleanly and easily, about 5 days work all told.

1983 Rival 41, tanks smaller at about 200l each. Replaced with 2 TekTanks for c. £1500 including all fittings and a couple of new gauges/senders.

 

[Tranona]

Some observations based on having the same problem. Cutting out the top and then turning it into an inspection hatch unlikely to work with the tank in place. You need to weld on a flange all round the opening and the hatch. The leak is almost certainly a corroded weld and will be difficult to trace and repair in situ, and not convinced an epoxy coating would be effective in sealing the leak.

My approach was to bite the bullet and remove the tank - took me nearly a week of sporadic work because it had been bonded in with expanding foam and I had to cut away part of the woodwork. However, once out I could assess whether it was possible to repair. The fabricator welded a reinforcing plate over the leaking seam, attached some mounting lugs and made a 150mm diameter inspection hatch at a total cost of £150. I glassed in a new platform for the tank to sit on and bolted it to a bulkhead and a glassed in floor plus a wooden beam across the top. It is now secure and perhaps more important is easy to remove should there be any leaks in the future.

If the tank had not been repairable a new one from Tek Tanks was £800. So taking it out gave me the option which to my mind is better than trying a cure that might not work and then having to take the tank out anyway.

 

[ytd]

Getting the epoxy to adhere to the stainless will be difficult and if it doesn't adhere the unsupported epoxy will easily crack. You could reinforce the epoxy with glass mat but by the time you have done this some of the other options look preferable.

 

[PCUK]

Get a thin walled GRP tank made to fit inside the old tank. It does't need to be particularly strong as the old tank will support to. Probably cost less in materials than the Epoxy coating and no worries about adherence to the stainless.

 

[Graham_Wright]

Get a thin walled GRP tank made to fit inside the old tank. It does't need to be particularly strong as the old tank will support to. Probably cost less in materials than the Epoxy coating and no worries about adherence to the stainless.

I believe there are crack finding sealants. Do a search.

 

[KellysEye]

>Not sure what good that will do when the OP is having problems with his WATER tank. Might do more harm than good.

Oops, sorry.

 

[coopec]

We amateurs should not use epoxy coatings in potable water tanks. The Gougeon(?) Brothers (West System) do not recommend it.
http://www.westsystem.com/ss/wood-epoxy-composite-tank-guidelines/

Why not give the the internal walls of the tank several coats of water based bitumen? Having used it on my water tanks I think it would stick to anything! AND it is approved for potable water.(Just google "water based bitumen potable water"

 

[coopec]

Can this be true? " The major long-term concern with any plastic water tank is extractives leaching out in the water"
Am I reading it out of context?
http://www.westsystem.com/ss/wood-ep...nk-guidelines/

 

[coopec]

Rainwater Harvesting - Made SIMPLE


It is well known that plastic has caused health problems in the past.

Below is a list of possible health problems that can result from human over-exposure to the chemicals used in various types of plastics.

asthma
birth defects
cancer
chronic bronchitis Use caution when choosing your rainwater harvesting tank
deafness
diabetes
genetic changes
hyperactivity
indigestion
infertility
liver dysfunction
obesity
skin diseases
skin rashes
ulcers
vision failure

http://oasis-rainharvesting.co.uk/fibreglass_versus_plastic_tanks

 

[coopec]

Liquid Rubber Product Demonstration

Liquid Rubber is a non-toxic, environmentally friendly anti corrosive waterproofing product. It is certified for potable water, and virtually odourless. It is water based asphalt emulsion, blended with elastometric polymers that are easy to apply, rapid curing and provide excellent adhesion to a wide range of building materials. Liquid Rubber products have excellent resistance against UV, ageing and cracking due to thermal cycling and chemical attacks. It can be applied by spraying, rolling, brushing or troweling.

Liquid Rubber can be used in conjunction with Supaseal heat reflective and trafficable topcoats and will provide and wide range of colours and years or maintenance free performance.






http://www.youtube.com/watch?feature=player_detailpage&v=xn9xmKsPsW4

 

[nigelmercier]

Liquid Rubber Product Demonstration...

That's pretty impressive.

 

[alahol2]

That's pretty impressive, never seen it in the UK though.

Would it work on a keel?