Dynamic head, SWCG and 24/hr pump operation.

[mas985]

First, it may be tough to find a pump that will only turnover your pool once in 24 hours. That is just 18 GPM, that means at high speed it will be 36 GPM. Unless, your head loss is very high, you will likely exceed that. The smallest two speed I am aware of is 3/4 HP. The 3/4 HP Whisperflow will produce 70 GPM @ 50 ft of head on high speed and 35 GPM on low. Twice what you have specified. However, two turnovers in 24 hrs is probably better anyway.

Also, you will still need to keep a some residual CL in the pool even though you will be running 24/7. With two turnovers, you don't want to have to wait 12 hrs before a bug is killed. So, you will still need some CYA to hold the chlorine during the day. How much is debatable but I would have at least 20 ppm. Trial and error may dictate how little you could get away with.

[sailork]

Thanks for the reply mas985 and oops on my part. I meant to turn over the pool twice in 24 hours or once every twelve I guess I just didn't proof my post..

I'm thinking that a good way to size a new pump is to calculate the gpm necessary to turn my pool over twice in about 20 hrs, make the best estimate I can of the total head of my plumbing at that gpm and buy a two speed that will do it on low.

I figured that I could cut the CYA down because I'd be constantly chlorinating.

[mas985]

It is probably easier to do your calculation at high speed since that is the pump you have now. Use your current filter PSI to calculate your head and figure a 5 hr turnover for high speed and that should be 2 turnovers in 20 hrs at low speed. The Whisperflow 1 HP will do a 5 hr turnover on high speed (assumes 55 feet of head). So I would say either a 3/4 or 1 HP. I would probably go with the 3/4 just to save a bit more on energy use given you will be running it 24/7. BTW there is only a 5 GPM difference between the 3/4 and 1 HP on low speed.