AboutJonathan Cauble Expertise I can answer all questions relating to outdoor water gardens. Anything from fish & plant health, water chemistry, and pond construction to equipment recommendations.
Experience I worked in a water garden specialty store for three years as assistant manager. I am also founder and president of Aquatech, LLC Aquarium Services of Virginia. I have personally troubleshooted over 100 ponds and countless aquariums.
Question I have purchased and dug out a 90 Gallon prefab pond. Tried to measure exact and back fill with sand. Problem 1 first rain pond rose out of ground 8 inches. Drained water from around pond dug out loose soil and backfilled again with more sand, layed 3 cinderblock inside pond while doing so. Rained again and raised cinder blocks 80 gallons of water and pond out 6 inches. What in the world am i doing wrong, the rain was minimal...
Answer I don't believe you are doing anything wrong, necessarily. It could be a result of your pond being in a low spot in your yard or even in an area of high-traffic runoff.
Typically, if a pond is located below the water level of your yard, you may get water under your liner. The solution could be as easy as raising your pond slightly and piling some dirt and rocks around the perimeter.
I would assume, by your problem, that your yard is sloping and/or has relatively loose soil. If these assumptions are true, then you may need to consider planting vegetation around your pond and talk to a professional landscaper. In fact, you may be better off hiring a landscaper to assess your yard and solve the problem in person. It's often times hard to completely analyze a problem without every little detail. Getting somebody on the site will save you a lot of time and words.
If it is determined that your yard is "doomed" from the start, there are a couple of siphon-related devices that may help you alleviate the problem. Also, consider a french drain.
