WHY ?
Economics - saving is insignificant. pennies.
Efficiency - would probably be reduced more than 50% (filtration
exponentially reduced, sediment increased)

A filtration system replicates nature (river flow) which is 24/7.
If you must - why not just use a timer (on 6 hours, off 6 hours)? better
yet - 2 hours on/off sequence to avoid possibility of filter stagnation in
summer months heat?

Hope this helps - Len.

"Gary Lieberman" wrote in message
...
I would like to vary the speed of my pump. During the night I would like to
slow the output by 50%. The pump runs on 220 volts. Does anyone have
experience with an electronic speed control that could be used with a
timer. Thank you