Draining your swimming pool or spa
What the law says
Here's what Bothell Municipal Code 18.04.260 says about emptying your pool or spa into a storm drain:
"It shall be prohibited and in violation of this chapter for any person or entity to:
A. Throw, drain, or otherwise discharge, cause or allow others under its control to throw, drain or otherwise discharge into the municipal storm drain system and/or surface and ground waters any materials other than storm water. Examples of prohibited contaminants include but are not limited to the following:
...16. Swimming pool or spa filter backwash.
17. Chlorine, bromine, or other disinfectants.
18. Heated water."
However, if you keep reading the code, it says pool and spa discharges are allowed as long as they have been de-chlorinated.
"b. Conditional Discharges. The following discharges shall not be considered illegal discharges for the purposes of this chapter if they meet the stated conditions or unless the director determines that the type of discharge, whether singly or in combination with others, is causing or is likely to cause pollution of surface water or ground water:
(3) De-chlorinated swimming pool discharges. These discharges shall be de-chlorinated to a concentration of 0.1 parts per million or less, pH-adjusted, and re-oxygenated if necessary and in volumes and velocities controlled to prevent re-suspension of sediments in the storm water system. These discharges shall be thermally controlled to prevent an increase in temperature of the receiving water. Swimming pool cleaning wastewater and filter backwash shall not be discharged to the surface and storm water management system."
So what does that mean?
It means you should de-chlorinate the water in your pool or spa if you're going to let it drain into a storm drain.
How do I de-chlorinate the water?
You have a few options.
- Simply stop adding chlorine to your uncovered pool and wait. Sunlight will help to naturally dissipate the chlorine within two weeks. During that time, use a swimming pool test kit to measure chlorine.
- Chemically de-chlorinate the pool water. Chemicals that will quickly remove chlorine are available through pool and spa care vendors. Follow the directions on the product label.
What do I do after I've de-chlorinated the water?
The most important thing is that you release the de-chlorinated water slowly. Pumping the water too quickly into the storm system can alter the pH, temperature, and suspended sediments in the nearest stream, having a negative effect on water quality and habitat.
Things to know about chlorine
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, its release into the environment is illegal and punishable by law. The federal Clean Water Act prohibits the discharge of pollutants to state waters. Even seemingly small concentrations of chlorine can harm or kill aquatic life. It's also against Bothell Municipal Code to discharge chlorinated water without first reducing chlorine to acceptable levels (< 0.1 mg/L). 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 de-chlorination products can become dangerous when brought into contact with other pool maintenance chemicals. (See https://doee.dc.gov/service/how-drain-your-swimming-pool-properly)