How long to run the pump, worked out rather than repeated

Where the eight-hour rule comes from

You will read “run it eight hours a day” everywhere, and it is not exactly wrong — it is just not about your pool. It is a rule of thumb aimed at inground pools of tens of thousands of gallons, where a single turnover genuinely takes the best part of a day. Applied to a 1,700-gallon above-ground pool it means running the pump for more than two complete turnovers, which is filtration you are paying for and not using.

The honest version is that run time should come out of your own turnover figure. Our pump sizing guide derives it: gallons divided by the published system flow rate. Once you have that number, run time is a decision rather than a guess.

When to run it, which matters more than people think

Two considerations decide the timing. The first is demand: chlorine is consumed fastest in heat and while people are in the water, so that is when circulation is most valuable. Running the pump overnight because electricity is cheaper is optimizing the wrong thing on a pool this size, where the total electricity bill is modest anyway.

The second is chemistry. Anything you add — tablets dissolving in a dispenser, shock, alkalinity increaser — only distributes if the water is moving. Adding chemicals to a still pool leaves them concentrated where they landed, which on a vinyl liner is how bleached patches happen. Our weekly schedule puts the chemical jobs and the pump schedule together.

What each hour actually costs

This is where a run-time decision becomes a money decision. From our pump electricity guide: at the EIA US residential average of 18.34 cents per kWh, every 100 W of pump run 8 hours a day for 120 days costs about $17.61. Reduce that to 6 hours and you have cut a quarter of it.

When to run it longer, deliberately

There are four occasions when the arithmetic above does not apply and you should simply run the pump continuously until the job is done.

Clearing cloudy water. A clarifier does nothing without filtration, and the whole treatment is dose-then-filter. Run it continuously until the water clears, then deal with the cartridge, which will have caught everything it had been missing — see our clarifier guide.

Recovering from algae. After shocking, filtration is what physically removes the dead bloom. Our algae guide covers the sequence.

After a heatwave or a busy weekend. Demand outran the routine; give the water extra circulation while the chlorine catches up.

Immediately after adding anything. A few hours minimum so it distributes rather than settling.

Fitting a timer without creating a hazard

A pool pump is an outdoor appliance near water, so the electrical requirements are not optional. Any timer has to be rated for the pump’s amperage and for outdoor use, and it must not defeat the GFCI protection the pump relies on. If your pump plugs into a GFCI-protected outlet, the timer belongs downstream of that protection, not in place of it.

If you are unsure about any part of that, this is the one job in this hub worth paying an electrician for. Everything else here is arithmetic; this part is not.

The reliable way to hold a schedule is not to remember it. Our pump timer roundup covers what to buy, what each hour a day is worth in electricity, and the three wiring requirements that are not optional.