David W

I would try to get around 6-8 times turn over through the sump, that makes it about 350 gph after headloss. A mag 5 would probably be fine for your situation. The larger mag pumps have a decent hum to them but the smaller ones are pretty quiet. The pump has a half inch line but it would be better to stick to the one inch line and put a reducer at the pump to reduce friction head loss.

A Mag 5 minimum. If the drain pipe is truly 1.5", you can go to a Mag 9.5 without concern of too much flow.

To reduce vibration, use spaflex on the return line (and a union!). You can apply silicone feet to the base of the pump the day before you use it, applying a dab to all four corners. Let it set up for 45 minutes, then place the pump on some wax paper. Let it cure overnight and you've just made some very inexpensive dampeners.

Thanks for the help!

Yes the drain will definately handle more flow than a mag 5, probably even a mag 12, but my point is why flow more. A larger pump will add more heat, make more noise and consume more wattage. The only reason i can see running a larger pump is if you regularly use a filter sock. Then your filter would benefit from a larger flow through. Otherwise i'd try to stick to 6-8 times turn over through the sump.

i agree that anything more than a mag 7, would be just more costly unless there are alot of restrictions in the plumbing system. but if you stuck to the 1 1/2 pipe size and used bushings at the pump that should provide more than enough flow. thanks marc i like the idea about the isolation feet, i've got a mag 12 thats very noisey.