Oh, I should have been more clear...every time the farm leaks you have to drain the whole vat that's leaking...there is no such thing as patching up "the leaky part" because you would never find it. So, as we just had a vat leak...we have one new painted one.

The others were done about five years ago. If you know where to look on the sides of the vat the dates they were last done are written on each.

The last time we did them we put in concrete...which has worked a lot better than wood!
I see, you aren't talking about the 2 part paint...you mean the one part fiberglass stuff, right? While it is cheaper than what we use, I know we had a big five gallon of that hung around so long I threw it away. (Like 8 years!) I didn't know why it wasn't what we needed, so I just looked it up because you made me curious, lol. I thought it just wasn't strong enough...but then I found this...
The Lowdown On Bottom Paint - BoatUS Magazine
Eeek...polishing effect...no good! Copper leaching? Ugh, no good either. Both at the same time? Worse! :/ Is this the stuff you meant, or were you talking about something else?
I was intrigued by the pond liner warranty...and looked it up, thinking hmm, bet they won't give me one...and sure enough, it says you have to use a special underlayment for the warranty to be valid....and if it was "punctured by a sharp object" (bound to happen) it also would void the warranty. :/
Always love ideas and suggestions, though, never know, might find something better! I sure wish the one part hull paint would work for us...sure would be cheaper than the 2 part!