Low flow high heat or high flow lower heat?


New member
Dec 23, 2017
New South Wales

First of all a big thank you to all the contributors. I found this site three years ago and follow the chemistry recommendations to the letter. No algae. For three years. Ever...... and it's easy! Oh.. and cheaper. Less chemicals and no pool guy.

Perhaps I could have some opinions on this conundrum. I have a heat pump that works at night. 10pm to 7am. Cheap rate electricity. Pretty warm at night in the summer in Australia. If I have the pump on a high flow the temperature differential between in and out is about 1.5-2.0 degrees C. If I have the pump on a lower flow through then the differential can be 2.5-3.0 degrees C. But then the turnover is lower and the reach into the corners is lower. Also, if the skimmer basket gets a bit blocked then the flow can drop below the threshold and the pump turns off.

What would you recommend. High flow or low flow. I would appreciate reasons as well. Helps me understand.

Merry Xmas to all



Well-known member
Jan 23, 2018
Canberra ACT
The ultimate answer will be what heat rise in the pool water do you get over the entire nine hour window vs the energy expended including pool pump and heat pump power usage.....
Theory says you gain some efficiency at higher flow rates but if that comes at the cost of increased power usage exceeding the efficiency gain then slow speed may be better.

You need a couple of similar nights. same overnight lows, same starting point on pool temp, measure the total power consumed from 10 to 7 and divide by the degrees rise in pool tmep.
Run one night on Low and one on High ... repeat a few times, average the results.

Then chose the low speed as it's quieter overnight :)
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