Originally Posted by RAH
I was unable to seal the lens with my backhoe because the sand flowed back in as fast as I removed it and I was afraid the ground under me would collapse at some point. It is possible that the sand back flushed but I would expect it does not. I assume that the polymer sealers would also fail if the flow reversed?

Correct. That's why it's important to be able to keep the water level high when using a polymer sealant. Positive pressure in the pond pushing outward.

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