To be honest that's what I was told at a build a pond day years ago, and have never had to test that theory. The one thing that you will have to do is cut your old liner to keep the hydostatic pressure from from building up between the two liners. I personally would pull the old liner out and look for places that need adjusting and use the old liner for a pondless somwhere else on the property. After ixing the hole of course.
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