Pool pumps, variable speed and how long to run one

A pool pump pushes the water through the filter to keep it clear and clean. It can be a home's second-largest energy user, costing as much as $310 a year. How fast it runs and for how long decide most of that.

Why speed matters

Filtering the water takes only half the flow that running a pool cleaner does. A single-speed pump is set for the cleaner's higher speed, so it runs faster than needed during filtering and wastes energy.

Variable-speed and multi-speed pumps can run slower for filtering and faster when the cleaner runs. The savings are large because energy use falls much faster than speed. At half speed, a pump uses about one-eighth as much energy.

Slower circulation also filters the water better, and puts less strain on the filter, plumbing and other parts, lowering the chance of leaks and repairs.

How long to run it

A timer cuts the filtering time. Running the filter 6 hours a day instead of 24 cuts its energy use by 75 percent. If debris is a problem, several short cycles through the day keep the pool cleaner than one 6-hour run. One long run leaves 18 hours for debris to collect.

Keeping water flowing

• Strainer baskets. Empty the baskets in the pump and skimmer often, so nothing blocks the flow.
• The filter. Backwash or clean it as the manufacturer recommends. Some filters backwash more often than they need to, and some designs don't need it at all. The manual gives the right routine.
• A cover. Covering the pool when it's not in use can cut heating costs by 50 to 70 percent. It can also cut chemical use by 35 to 60 percent and water loss by 30 to 50 percent. It also keeps out dirt and debris.

A spa

Keep the cover on until you get in, and put it back when you're done. Run the jets only while someone's in the water, since the air cools it quickly. For a spa used weekly, lowering the temperature 3 degrees between uses saves about 5 to 10 percent of the heating cost.

An annotated example

What to do next

Note how many hours a day the pump runs and at what speed. Set the timer for the filtering the pool needs, and empty the strainer baskets so water moves freely.