How to figure run time for 2-speed pump?

I have a new 18000 gal. IG pool/spa combo. I had a Sta-Rite 2 speed pump put in, it's 1 1/2 HP in high and 1/4 HP in low. I am trying to figure out the best run times to make use of the cost savings. The installer told me that normally for a regular pump and my size pool that 8 hours a day, split up over two four hour periods, was sufficient. What I decided on, for now until I know better, was two 6 hour periods, and each of those periods is split in half between high speed and low speed operation. Basically I traded 4 hours of high speed operation for 8 hours of low speed operation. I'm wondering if that really saves me a lot of money and if I am getting the same amount of filtration. Sound right? Any suggestions? The water looks great, btw. I was even tempted to decrease high speed times even further, but the pool cleaner does not work in low speed, so I'm not sure that's a good idea.

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.

If my 1.5HP pump has the same flow rate as yours in both speeds (this is just a guess til I find out) than I am changing the water over between 2 and 3 times per day. Currently the temperatures are in the low nineties and the pool holds between 80 and 86 degrees during the day. Does this rate of turnover sound like overkill?

Sort of overkill, but if it keeps you pool clear then it's ok. I would just run it in low for a longer time becasue it is cheaper and most filters work better at a lower flow rate then a higher one. Sounds like 12 hours on low should do the trick for you.

There are a lot of things to consider. Do you have any features that require the pump to be on high speed to operate properly? Automatic cleaner or In-floor cleaning? If not, can you get the circulation you want without running on high speed at all? Maybe you only need to run on high speed when you want to quickly skim some debris from the surface?

I have a 2 speed pump, and my pool builder sucessfully sold me on the benefits of 24 hour-a-day circulation. Public pools are required by law to have 24 hour circulation. I run on high speed a few hours in the AM when I am likely to be adding acid. A few hours in the middle of the day to increase the flow through my redneck solar in the peak of the day, and a few hours in the afternoon when we're most likely to be in the pool and might want to turn on the fountain or sheer descent. The rest the time I run in low speed. My water is continuously filtered and sanitized by the SWG which I run at a much lower percetage. I know my circulation is overkill, but it only costs me a few extra $$ a month and my pool always looks great