FIBERGLASS water tanks: Flow coat or bladder

[gary789]

We have a 2003 Perry 43 cat. Recently discovered both our 450l fiberglass water tanks have the flow coat lining peeling off. They are an integral part of the hull
There is very small access into the tanks with out cutting out the floors and the top of the tanks.
Wondering whether putting in a bladder or recoat with flow coat or any other options?

[Chotu]

Bladder would be my vote. the tank is ok. You just need back liner. A coating needs prep work to apply. A bladder is just stuffed in there and ready to go..

[BenBowSirocco]

I might suggest sand blasting. I also found an oscillator with carbide tip on a stick very useful. We dealt with the same situation on our boat a few years back and the oscillator worked a treat. An old antenna base with adjustable locking position was very useful. We had decent tank access though.
We then followed the West System guidelines and did 7 coats of epoxy very precisely mixed on a gram scale and heat cured with a hair dryer.

Whatever you do, do not use any sort of chemical based remover, it will attack the resin system of the glass hull.

[mikedefieslife]

On Prouts I'd say more people repaint usually with a 'food safe' epoxy if there really is such a thing. The problem with bladders is the lack of baffles. I don't know about your cat, but I think some of the baffles in the Prouts are also structural.

[philiosophy]

Sure glad to see somebody bring this up. I will be hauling out in the next few months. I have the same problem with the aft tank on my Southern Cross 39. I don't know if I could get a bladder in there. If you could I wonder if there are any problems associated with a bladder like say loss of capacity, or mildew, what have you.

[mikedefieslife]

Loss of capacity for sure. It's not in a tank but I have bladder I use for filling up in the dinghy. It's 100l. You could not get more than 80l in it without pressurising it. Then it's like a huge ballon.

If you go with a bladder, they are robust, but it also pays to add some nice smooth anti-chaff material to the walls.

I can't see mildew being any more of a problem than it would be with other vessels.

[Kiwi.]

Often, in fact most often, when a flow coat starts flaking it is because there were some delays in application which resulted in effectively two thin coats of flow coat being applied instead of one thick coat. This is not uncommon in production boats when the applier goes to lunch or to "smoko". A flow coat cannot be applied over a flow coat without significant surface preparation (mainly sanding). If you can get an endoscope camera in there and if you can see a clean (no fiber ends) surface where it's flaked, then the two coat problem is certainly likely. If so, and if there is no taste change in the water, install a filter to catch the flaking top coat and forget about it. We did this on our production yacht and the filter caught bits of flow coat for a couple of years then it all settled down again.

[Kiwi.]

Just to add to my above post regarding the "twin coat" problem, the other reason I've seen flaking flow coat is because the builder did not sand the fiberglass before applying the flow coat. Ironically this may be good news if you have flaking flow coat in a water tank. If it wasn't sanded before the flow coat was applied then there is a good chance there are no, or minimal, fiber ends exposed when the flow coat flakes off. So the water will not be getting into the fibers. In which case the "do nothing" solution works great. Once again put in a filter and wait; there is probably no problem. Remember the main reason that builders use flow coat inside your tanks is that otherwise your water tastes like fibreglass for a year or two. My first yacht (a new 6.2 meter Beachcomber) had no flow coat in the water tank and the taste was awful but there was no structural or safety issues. If your taste is OK and you can't see cut fiber ends, don't worry about it.

[mvweebles]

My hunch is a bladder is one of those things that works better on paper than in practice. Getting the fittings in place might be a challenge and you'll likely greatly reduce your capacity.

Any chance you can get enough access to steam clean interior to remove as much coating as possible, then spray a new coat using a wand of some sort?

Good luck with this one.

Peter

[onestepcsy37]

i had a leaking water tank on my csy 37. the tanks are port and stbd in the main salon and are acually the entire bench seat. capacity 60 plus gallons each. the stbd side tank had a slow but noticeable leak. i was pretty sure it was low down in the tank because it eventually almost drained itself out.

fortunately tank access was great and i simply cleaned out the tank, lightly sanded it and vacuumed that out and then gave it two coats of epoxy,.
end of leak.