Swimming Pools
The water in swimming pools must be treated with chlorine to kill possible pathogens and protect human health. Even at extremely low levels, chlorine can be toxic to aquatic animals and plants. When draining a pool, the water must be discharged to the public sewer not to a storm drain. Learn more about regulations to protect stream water quality while draining pools (PDF).
What You Can Do:
Use the following guidelines when discharging swimming pool water:
- Pool water must sit for at least 48 hours after the addition of chlorine, or until the chlorine level is below 0.1 milligrams/liter. Chlorine concentration should be tested using a standard pool chlorine test kit prior to discharge.
- The pH of the pool water must not be less than 6.5 or greater than 8.5 at the time of discharge.
- The pool water must be free of algaecide at the time of discharge. Algaecide can severely affect normal algae and plant growth in streams.
- The water should not look murky or cloudy. Solids suspended (or particles) in the water must be below 60 milligrams/liter. The best way to achieve this level of clarity is to allow visible particles to settle out of the water. The material settled out should not be discharged with the water.
For community pools in areas served by public sewer, pool water must be discharged to the public sewer and must not be discharged to a storm drain. For residential pools, backwash water must be discharged to the public sewer. If your only option in draining pool water is to discharge directly into the environment, the water being discharged must comply with the State of Maryland Water Quality Criteria.