Ask how long to run the pump and the answer used to be a flat eight hours. That came from single-speed pumps and a rule of thumb about turning the water over once a day. Variable-speed pumps changed the math, and the real answer now is longer, slower and adjusted by season. Here is how to think about it.
Turnover is the starting point
Turnover is the time it takes the pump to move the pool's entire volume through the filter. One turnover a day is the traditional minimum, and it does not mean every gallon has been filtered; some water goes through several times and some barely moves. More turnover means cleaner water, up to a point. The pool's volume and the pump's flow rate at a given speed give the turnover time. Plumbing and hydraulics explains why the pipe size and the filter change that flow rate.
Single-speed pumps
A single-speed pump runs at one speed and one power draw. The only variable is hours. Eight to twelve hours in summer and fewer in winter is typical, and every hour costs the same. This is the pump that made pools expensive to run, and it is the reason variable-speed pumps have taken over.
Variable-speed pumps
Power draw drops dramatically as speed drops, far faster than flow does. Halving the speed cuts flow in half but cuts power to a small fraction. So a variable-speed pump running slowly for many hours moves as much water as a fast pump running a few, at a much lower cost, and the filter works better at lower flow. Variable-speed pumps and energy costs goes through the numbers.
A typical summer schedule looks like: a low speed for most of the day for filtration and circulation, a higher speed for an hour or two to run the skimmers hard and the cleaner if it is suction or pressure side, and whatever speed the heater or salt cell needs during their windows. The pump may run twelve to twenty hours a day and still use less power than a single-speed pump running eight.
What else sets the minimum
- Salt chlorine generator. The cell makes chlorine only while water flows. The generator's output setting and the hours of flow together determine the day's chlorine. Not enough hours and the pool runs short, no matter how the cell is set.
- Heater. Needs a minimum flow to fire. During heating, the pump has to run at least that fast.
- Suction and pressure cleaners. Need flow to work. Schedule their window at a higher speed.
- Water features. A waterfall or deck jets usually need a higher speed or their own pump.
- Skimming. Skimmers need decent flow to pull debris off the surface. A low-speed schedule that never gets above a trickle leaves leaves floating.
Summer
Hot water, strong sun, heavy use. Chlorine demand is high and algae is looking for a still corner. Run long: most of the daylight hours at low speed, with a high-speed skim window. On the hottest weeks, or after a party, extend the hours. Circulation during the day is what matters; the pool does not need much at 3 a.m.
Shoulder seasons
Spring and fall in the Piedmont are the pollen and leaf seasons. Skimming matters more than filtration for a few weeks. Keep the daytime hours and give the high-speed skim window more time. Surviving pollen season covers the spring problem specifically.
Winter
A pool that stays open through winter in North Carolina needs little sanitation and a lot of freeze protection. Run a few hours a day for circulation and chemistry, and make sure the freeze-protect function is set so the pump comes on automatically when the air temperature drops near freezing. Moving water does not freeze in the pipes; still water does. Freeze protection is the post to read before the first cold night.
Setting the schedule
Start with a conservative schedule, watch the water for a week, and shorten or lengthen. Clear water and steady chlorine mean the hours are enough. A dull look, a chlorine level that will not hold, or debris on the surface all mean more hours or a higher skim speed. Automation makes the seasonal changes a few taps instead of a trip to the pad.
We spec pumps and set schedules on every pool we build across the Triad, including Greensboro and Trinity. Reach out for a free consultation if you are building or upgrading equipment.