Quote Originally Posted by pauster
Hi Mark,

now what happens in 1 1/2 inch pipe where it supposedly gets ugly beyond the 42 gpm ? If I had over 60 gpm going through that pipe today the velocity of the water could be detrimental to the piping ?

Theoretically, it could slowly wear out the interior of the pipe but I have never heard of a case.

Just looking at the smallest pumps availabe - I was aiming for about 40 gpm at 40 ft of head. Most pumps go beyond that.

Of course if I am getting more than 40 gpm today (say 60 gpm) then my new head at 40 gpm would be lower: 40 / (60/40)^2 - right ? So head at 40 gpm is around 17.8 ft ?

Right so most single speed pumps will be well beyond that. But as the calculations showed earlier, multi-speed pumps at lower speeds should be in that range. Target a 3/4 HP 2-speed or multi-speed pump and you should be OK. The Whisper flow 3/4 HP I did the calcs for earlier should be about 33 GPM at low speed.

Also, sometimes it is good to have a high speed to mix up and distribute chemicals before a quick swim.

Patrick

See above for answers