How to figure run time for 2-speed pump?

[gwrace1]

You need to completely cycle your water at least once per day. To do this You need to know the Gallons per Minute ratings of your pump(s) in both speeds.

As an example I have a two speed 1.5 HP pump that turns over 80 GPM in high and 40 GPM in low. I wanted to run the pump in low speed as it only pulls 3.8 amps. In low the pump will turn over 2400 gallons per hour. For my 26000 gallon pool that requires about a 11 hour run time. I actually run the pump about 12 hours each night. I've only noticed about a $30 per month increase in my electrical bill since firing up the pool in early March and some of that could be attributed to the 90 degree temps we've been seeing in central Texas.