Should also add that one has to account for the work & learning curve associated with different sealers. Beginners sometimes mess up mixing epoxy properly and wetting out fiberglass is really no fun at all.
The rubber type coatings can be pretty thick but no accurate mixing is required. But they take more coats and there is the glass or acrylic installation issues since silicone won't stick to it and it won't stick to silicone.
Sheet plastics would require accurate cutting but more importantly very careful attention would need to be paid to the corners which take a lot of stress in a tank. And silicone does not bond super well with many plastics.
Polyester and vinyl ester resins have horrible solvent odors and can gum up quickly if too much catalyst is added. But they are cheap and a good way to build a composite structure and get a good thick layer of protection.
Epoxy paint, like Sweetwater, are easy to apply and real world results suggest they waterproof well at thin dry mil thickness' which brings the cost down. But again they have a solvent odor issue and require haz-mat shipping.
So my point is that there is no perfect sealer.
I've built plywood tanks with epoxy resin, epoxy paint and fiberglass resin. Never used the rubber/bituminous compounds on plywood but have applied them to concrete walls. I've also applied drylok to walls and have used it to seal a plywood cage. I've built cages out of sheet plastic but never lined a water holding tank with them but have a good idea of how I'd do it. The upshot being is I think they all have their downfalls regardless of cost.
Short of paying somebody a lot of money to spray with polyurea, I don't know what I'd use if building a large plywood tank today.
The rubber type coatings can be pretty thick but no accurate mixing is required. But they take more coats and there is the glass or acrylic installation issues since silicone won't stick to it and it won't stick to silicone.
Sheet plastics would require accurate cutting but more importantly very careful attention would need to be paid to the corners which take a lot of stress in a tank. And silicone does not bond super well with many plastics.
Polyester and vinyl ester resins have horrible solvent odors and can gum up quickly if too much catalyst is added. But they are cheap and a good way to build a composite structure and get a good thick layer of protection.
Epoxy paint, like Sweetwater, are easy to apply and real world results suggest they waterproof well at thin dry mil thickness' which brings the cost down. But again they have a solvent odor issue and require haz-mat shipping.
So my point is that there is no perfect sealer.
I've built plywood tanks with epoxy resin, epoxy paint and fiberglass resin. Never used the rubber/bituminous compounds on plywood but have applied them to concrete walls. I've also applied drylok to walls and have used it to seal a plywood cage. I've built cages out of sheet plastic but never lined a water holding tank with them but have a good idea of how I'd do it. The upshot being is I think they all have their downfalls regardless of cost.
Short of paying somebody a lot of money to spray with polyurea, I don't know what I'd use if building a large plywood tank today.
