Quote Originally Posted by Service Guy
Dual speed pumps are more designed for spa use only and rarely serve any purpose on a pool/spa combination. About the only time a dual speed motor would be installed on a pool/spa combination is if your were going to continue using the spa after the pool is winterized. In that case, the filter NEEDS to run whenever temps get near freezing and continue to run until the temps rise above freezing. In this part of the country that could be weeks at a time. Then, a low speed pump would be more economical. Other than that, I'd stay with a single speed pump. In addition, it'll be less expensive to replace when it dies!

I have to disagree with this view point. Many 2 speed pumps are installed for a pool spa combo. In fact, many on this forum have that configuration. It is more cost effective to filter on a low speed when you do not need the HP for the spa jets. In a 2 speed pump, low speed is generally half the GPM but 1/3 the cost to run so net net, you are much better off for filtering on low speed.

Here is another thread on this same topic:
http://www.poolforum.com/pf2/showthread.php?t=806