A plumber, who advised that I could do the job myself, said that I needed to replace an existing exterior sump pump and basin for drainage of stormwater from our lawn. There has always been a lot of ponding due to underlying clay. The exterior pump system discharges through 1 1/2" PVC piping to a sump pump system in our crawl space that then discharges to a stormwater drain on the other side of our yard. My prior Flotec and similar Home Depot-bought pumps kept dying after one season. I was advised to enlarge the pit diameter to reduce the frequency of the on/ off cycle. I dug a 30" deep hole and installed Jackel (resin?) 18" dia. x 24" deep basin and a Storm Pro 1/2 HP Cast Iron/Stainless Steel pump with vertical magnetic float and built-in release hole to avoid air buildup. I lined the bottom of the dirt pit with about 6" of gravel. I drilled about 60 - 1/8" holes around all sides of the basin in 3 rows in about an 8" band that started about 1" from the bottom. I then covered the outside of the basin with landscaping weedblock fabric. After inserting the basin in the ground, I poured a 5" diameter layer of gravel all around the sides of the basin from bottom to top, so that I had the gravel as an outer filter and the fabric as an inner filter. The Storm-Pro had a 2" discharge hole so I used a 2" to 1 1/2" adapter to connect to existing plumbing, which had a check valve. All clamps were tightened properly and the check valve was in the proper position. I rested the pump on four bricks in the bottom of the basin to give it a little elevation from sediments. I tested the pump by pouring water in the pit and it appeared to be working. I then closed the lid and put two more bricks on top to keep the basin lid shut without having to mess with unscrewing for service.I went out to check it after some heavy rain and found that the entire pit had pushed out of the ground and was bobbing on the surface of a full pit of water! I heard the pump running, so I unplugged it. After everything dried out, I went back and looked. The filter fabric did not seem to be clogged, but about 10 to 15 of the 60 inlet holes appeared to have sediment or tiny gravel particles. (Filter fabric may not have been glued sufficiently?) That would still leave about 45-50 inlet holes. If the pit was filling up with water, that should ADD weight along with the 6 bricks. I can only think that somehow the pressure under the pit must have been greater than the pressure inside the pit. I would think that would only occur if all the holes and/or the fabric had been clogged. I am scratching my head about this. Any good suggestions? Thanks much.