Pump Sizing

  • Last Post 15 May 2018
mgGS350 posted this 06 May 2018

Hello and thank you for providing this forum. I am trying to figure out if a variable speed pump is right for my pool. The pool is 6600 gal, it has a C900 Hayward filter, Pentair 340038 1hp pump with Pentair Solartouch for the solar heat. I have gauges on the pump showing TDH @ 57' while heating and 45' when not. Looking at the curve for my pump that is about 40gpm, it is showing about 8.7 amps. My question is as I look at the curve for a variable speed pump, to get 57' of head the pump speed is not that much different. I do live in Florida but my wif likes the water really warm so the solar gets used a lot. I mainly want the variable speed to quiet things down. Any advice will be appreciated.


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InyoRob posted this 07 May 2018

Hello MGGS350 - When looking at the pump curves for variable speed pumps, you have to take into account that the feet of head drops when you lower the speed. This has to do with the pump affinity law. The head changes proportionally to the speed squared.

Let's say you reduce the speed by 50%. This means that the head will be 25% of the full speed head. In your case, you can multiply 57' of head by .25. That gives you 14.25' of head when running the pump at half speed. 

We'll look at the pump curve for the Pureline Prime 1.65 variable speed pump. At 1800 rpm the pump will push approximately 33 gpm at 14.25' of head (splitting the difference between 42 & 24").

The noise of the variable speed pumps drop dramatically as you start to reduce the speeds.


mgGS350 posted this 15 May 2018


Just to be sure I am clear, the Pureline Prime 1.65 is the pump I can use. I plan on adding a chlorine generator at a later date, is there enough room in there (capacity wise) to add that? And since I am asking questions can this pump receive signals from my Pentair Solartouch?

Thanks again.



InyoRob posted this 15 May 2018

Yes, you could use the Pureline Prime 1.65. The Solartouch won't communicate with the Prime. You'd have to go with a Pentair Intelliflo if you want to communicate with the Solartouch.

I'm not sure I understand the question about the Prime and a saltwater system. The Prime doesn't have an Aux connection to connect the salt system. You'd have to wire both to the same timer.