Non toxic sealant / paint

[andrew lyner]

I have recently completed a pond with butyl liner with large pebbles round the edge. The stones are set in mortar. It looks nice apart from the change in colour from butyl to mortar to pebbles. Because it's elevated and made of pebbles, the edge of the mortar layer is not even. I need to bring the water level up to the pebbles if possible but when I fill it up, the level soon sinks to a lower level. Is there a black paint that I can use to seal the mortar and not make the water toxic?

 

[Meyer Jordan]

Any marine sealer or epoxy coating is safe.

 

[andrew lyner]

OK thanks. And will it bond onto the butyl? (Assuming I clean it up)

 

[Meyer Jordan]

You inquired about a sealer or coating for mortar. I know of no sealant/coating that will bind to EPDM and mortar.Two entirely different bonding requirements.

 

[andrew lyner]

A misunderstanding: in the post I asked for something to seal the top of the pond which has butyl with pebbles held in mortar, so the water can come up over the mortar without leaking out. If I use an epoxy to colour and seal the mortar then that will do the main part of the job. There will only be a thin gap between the turned over butyl and the mortar laying on top of it. I would imagine that would not be a source of major leak, compared with the whole area of the mortar which can take in water. I guess I'll have to try a smear of black silicone sealant over the gap. I don[t have any expensive fish in the pond and the plants should be able to handle most things chemical, initially.
I'm surprised this isn't a more common problem when people cap the edges of a pond with irregular stones. I'll have to experiment with a spare bit of butyl.
You are right about the bonding requirements. I would use bitumen, which would stick ok but I wonder about the nasty solvent.

 

[Meyer Jordan]

You do not want Bitumen or similar petroleum substances anywhere near an aquatic habitat of any type.

Methods "b" and "d" in the below image are most often used as edging treatments.
You apparently used similar to method "a".

 

[andrew lyner]

I was joking about the bitumen. Thanks for those diagrams.
Unfortunately I didn't think very hard about the capping of the pond. I should have looked it up first. The surrounding wall is fairly narrow and I couldn't think of a way to take the liner any higher than it is. Having made my bed I have to lie in it. The epoxy will probably do the job and there is only a few cm max of hydrostatic head. Worst comes to the worst, I may resort to Captain Tolley's Creeping Crack Cure (yes there is a real product called that. An owner of an old boat would never be without a bottle of it.