What size pool pump do I need?
Pump size is set by pool volume, the turnover you want, and what the plumbing and filter can actually handle. An oversized pump costs more to run, pushes water through the filter too fast to clean it well, and strains the plumbing. Matching the pump to the system beats maximising horsepower.
What sizing depends on
- Pool volume in gallons and the turnover time you want
- Pipe diameter and run length, which cap safe flow
- Filter rating — pushing past it shortens media life and lets fines through
- Extra features: spa jets, waterfalls, solar panels, in-floor cleaning
Why oversizing backfires
Water forced through a filter too quickly does not get filtered well, and the higher flow drives up both power draw and wear. An oversized pump on undersized plumbing also makes noise and cavitation more likely.
The variable speed advantage
A variable speed pump largely sidesteps the sizing argument. You set a low speed for daily filtering and a higher one for vacuuming or spa jets, so one pump covers both jobs without running at full draw all day.
If a pump is failing, that is the moment to size correctly — replacing like for like just locks in whatever the last installer chose.