How to Properly Discharge and Dechlorinate Swimming Pool Water

Drain your pool wisely.

District of Columbia law prohibits the discharge of swimming pool water onto public or park space. The penalty for a first offense is up to $1,000, and doubles for each subsequent offense. The municipal separate storm sewer system, or MS4, was designed to handle runoff from rain and snow only. The MS4 pipes water directly into receiving rivers and streams. If this water contains chlorine, it can kill aquatic life.

Swimming pool water must be discharged into a sanitary sewer system that meets the standards of the District of Columbia plumbing codes and District of Columbia Water and Sewer Authority pretreatment program.        

Guidelines for Owners of Residential Swimming Pools

• Download our flyer about swimming pools [PDF]

Dechlorinate pool water before discharging into a sanitary sewer line.

Reduce chlorine in the pool water to undetectable levels (<0.1 mg/L) before draining it into the sanitary sewer system. Consider the following options for removing chlorine:

• Simply stop adding chlorine to your uncovered pool and wait. Sunlight will help to naturally dissipate the chlorine within 10 days. During that time, use a swimming pool test kit to measure chlorine.
• Chemically dechlorinate the pool water. Chemicals that will quickly remove chlorine are available through pool and spa care vendors.

The chlorine in your pool provides benefits, but must be handled wisely.

Chlorine is one of the most common chemical additives used to control bacterial growth in swimming pools. With proper chlorination, swimmers can allow pool water to contact the skin and incidentally swallow some pool water with little fear of infection. But as beneficial as chlorine can be in controlled situations, its release into the environment is illegal and punishable by law*.

• Even seemingly small concentrations of chlorine can harm aquatic life. Chlorine can be very toxic to fish, small crustaceans, and plankton. The U.S. Environmental Protection Agency acknowledges that at 1mg/L or less chlorine has a high acute toxicity to aquatic organisms.
• It is against District and federal law* to discharge chlorinated water without first reducing chlorine to acceptable levels (< 0.1 mg/L). The federal Clean Water Act and the D.C. Water Pollution Control Act prohibit the discharge of pollutants to the waters of the District of Columbia.

A pool test kit will help you to monitor chlorine. Some test kits will allow you to measure other important water quality parameters like pH, hardness, and alkalinity in addition to total and free chlorine.

Follow the chemical use, handling, and storage instructions carefully, as some dechlorination products can become dangerous when brought into contact with other pool maintenance chemicals.

Discharge dechlorinated pool water to a sanitary sewer system.

Unlike the MS4, the sanitary sewer system carries wastewater to Blue Plains Wastewater Treatment Plant for removal of harmful pollutants before it is discharged to the Potomac River.

• Unless your swimming pool is directly connected to the sanitary sewer for easy drainage, consider using other sanitary sewer connections in or around your home.
• Use a pump and hose to drain pool water into plumbing fixtures connected to the city sanitary sewer system.
• Seek the advice of a licensed plumber concerning the appropriate flow rate for pumping water into the plumbing fixtures.
• Be prepared to call a plumber immediately if draining the pool causes a back up to the sanitary sewer system.
• It is illegal to drain swimming pool water into any public or park space.

*(Swimming pool water discharged into public/park space is scheduled as a Class 2 civil infraction in Title 16 of the District of Columbia Municipal Regulations, Chapter 33, Section 3306.2.2(c). The maximum penalty for a first offense is $1,000. It is also a violation of the Water Pollution Control Act to discharge pollutants, unless permitted, into the storm drains and waters of the District.)

Do not direct pool water discharge to a private septic system. When washing pool filters, discharge the wash water to the sanitary sewer system. Depending on the type of filter, it might be as appropriate to throw the used filter in the trash for solid waste disposal.

A note about chloramine.

Chloramine, a disinfection product added to D.C.’s potable water supply, is toxic to some aquatic life. It is more stable than chlorine and will not readily dissipate by sitting or aerating. If you have added chloraminated city water to your pool in recent weeks, consider chemically treating the pool to remove chloramine. Look for products specifically formulated for chloramine removal.

Any questions?

To report possible discharges, please call the District Department of the Environment’s Water Quality Division at (202) 535-2600.