I am in the process of building a Disappearing Water Fountain in my front yard flower bed. I decided to use a preformed 50 gallon plastic pond insert from Lowes. I dug the hole and set the insert into it and then back filled with dirt and gravel. I then laid a pond liner sheet over the insert, then cut a hole around the inside perimeter leaving about a four or five inch overhang. I then cut off the outside perimeter, about a foot or more all around it. Next thing was to build a cement border that would hold a plastic drum grate on which to set the rock fountain. After it was all set up with the water in the pond and the pump hooked up to the rocks (three of them) I tested it out. Everything ran well. I then added small pebbles and rocks around the base of the larger fountain rocks and let it run all night.
When I awoke in the morning, I found that the pond had run dry enough that the pump was sucking air. Upon deeper investigation, I found that the water had seeped around and underneath the pond insert, causing the pond insert to buckle up in the middle and on the sides.
I removed the concrete border, plastic pond insert and basically excavated the whole area. My new plan is to put in an actual disappearing fountain basin that is 44" X 44". It will be slightly elevated from the rest of the flower bed (maybe 4 or 5 inches). My biggest concern is that if not set up properly, I will end up with the same situation of water getting underneath the basin. I have considered laying pond liner sheeting around the perimeter of the basin (either on top or underneath) then sealing it with black foam insulation designed for rock wall sealing. Any suggestions or recommendations would be very helpful. The whole project has been put on hold due to the almost daily inundation of rain filling up the hole. The attached pics show what it looked like before I started, then laying in the insert, then the rocks (hypertufa rocks) and the grate without the rocks. I do have a short video of what the initial startup looked like.
