I bought the 1 HP as a replacement for a broken spa pump. The original was no longer being manufactured, and direct replacements were $250-300, so I figured I'd try this one instead, expecting some extra work with the plumbing. However, all the plumbing parts fit - all I had to do was bolt a piece of wood underneath, since the mounts were lower than the original. This pump is extremely quiet - at least compared to the original - I have to be standing right next to the spa to hear anything at all. So far I am very happy with this purchase.