I bought this pump to replace a Hartell pump that was in the house when I moved in 6 years ago. The float switch on the Hartell had failed and was uneconomical to replace (much like the entire Little Giant pump). The mounting slots are exactly the same and lined up with the existing holes where the old pump was installed. The inlet where the drain enters the pump is slightly different. If I had a flexible drain hose this would not be a problem and the installation would be a complete bolt on procedure. But since my pump drain was rigid PVC, I had to drill new holes in the wall slightly to the left to install the new pump without bending the PVC drain. It only took a few extra minutes. A few people have reported problems with their check valves. I did not do it. Mine worked fine from the start. As the pump ran, I watched the water flow through the clear vinyl tube and after the pump shut off it continued pumping through the tube for a few seconds leaving only a few inches of water above the check valve. On the old Hartell pump I removed and modified the check valve (using a 1/4" x 3/8" NPT brass fitting and a short length of 1/2" ID vinyl tubing). I have this second check valve some Fitted inches above the factory valve Admittedly I didn't really need it at the time but with several people reporting failures I figured having a second valve as a backup would increase the overall reliability of the system.