Currently i'm using Pinnacle/Purex Triton 1 HP Pump for my 18 x 40 inground pool. This year the pump is really loud. I'm planing to replace this to "Pentair WhisperFlo 1 HP 2 speed pump (WFE-4)". Is this pump OK for me? Do I need more horsepower like 1.5 HP? Also I have a timer to turn on and off for my pump. If i replace to this 2 speed pump, is my timer OK? because i heard someone said this pump without the switch on the pump for high and low speed. If this is true. How i use this? I'm thinking to run at low speed and only use high speed for pool vacuums.