How to Backwash a Swimming Pool Drain Into the Sewer

Turn off the pool heater, if applicable, as well as the pool filtration pump. Wait at least 15 to 20 minutes after turning off these accessories before proceeding with the backwash.

Check the water level in the pool; you want it to be completely full. Running a hose into the pool to supply additional water during the backwash is helpful.

Locate the sewer access suggested by your local authority. Typically, this is a sewer clean-out hole – a pipe covered with a threaded cap 3 or 4 inches in diameter. This may be in the ground near the edge of the property, closer to the house or even on an exterior wall of the home, near a plumbing fixture.

Uncap the clean-out. Run a backwash hose or, in a pinch, a pool vacuum hose attached securely with a hose clamp, between the backwash discharge port on the pool pump and the clean-out. Stick the free end deep enough in the clean-out to avoid it popping out during use.

Add any additional sand needed in a sand filtration system. Doing so before backwashing allows the sand to settle down before using the pool.

Turn or move the valve or lever on the filter from "filter" to "backwash." Occasionally terms may vary, but the meaning will be clear and the way to move the selector obvious.

Start the pool pump again and immediately check inside the house for signs of water backing up into the shower, sinks or toilet. Enlist a helper who can watch for this as you open the backwash for best results. If water backs up inside your house, you either have a block in your sewer clean-out line, which must be eliminated, or the water is flowing too fast for the line to handle. Local authorities generally recommend a flow rate of 10 to 12 gallons per minute or less.

Look through the clear sight glass, if your filtration system features one, to see the color of the water discharging through the media. It should turn from a dirty brown color to mostly clear in a minute or two. Stop the pump after about 2 minutes, or until the water is clear. Don't exceed more than 4 or 5 minutes to avoid wasting excessive water.

Turn the valve or lever to "rinse" and turn the pump back on. Let it run another minute or two; this settles the sand in the filter, if it's a sand filter, as well as preventing dirt residuals from returning to the pool.

Stop the pump again. Turn the setting back to the original position -- typically "filter" -- and add additional DE, if used, according to manufacturer's instructions.

Disconnect the backwash hose and close the clean-out opening. Turn off the water flowing into the pool, replacing water drained during the backwash, when it reaches the proper level.