I wish I'd found this site long ago....
A few years back I replaced a dead motor with a 2-speed whisperflo (1.65 SFHP). I find that at low speed, even running 24 hr/day, I don't get good filtration. At high speed for 10 hrs/day I can. (One difficulty is that in summer my pool can get > 90 degrees.) I know the ancient 1.5" plumbing limits things, but I would expect it is better at slow speeds. Is there a maximum head or minimum pump rpm threshold causing me troubles?
I tried this with both my DE and sand filters. I have both in parallel, as I found my sand didn't filter algae well enough. Now I just run my low speed pump constantly through the sand and a std. motor on a DE filter for some hrs in summer and to vacuum.
Sand filter: Hayward 3.1 ft^2
DE: Hayward EC75
-Thanks for advice!