Sewer Guidelines for King County

corroded sewer pipe (18K)

It can be okay to dispose of certain dilute solutions of chemicals in the sink according to the rules.

If your chemical is hazardous waste, it cannot be disposed of in the sink. Refer to the UW Lab Safety Manual Section 3, which shows how to calculate at what concentrations your mixture of chemical is hazardous waste. Or, send in a Waste Evaluation Request and EH&S will advise you.

If you are at UW Bothell or UW Seattle, also refer to the following tables and rules for limits on some specific chemicals. These rules were designed to protect the Puget Sound and biosolids produced at the wastewater treatment plant and then sold as fertilizer. Note that the pH limit is 5.5 - 12 in order to protect King County's pipes, which are easily corroded by acid.

If you are at UW Tacoma, at this time disposal of your non-hazardous waste in the sink must be approved on a case-by-case basis by the City of Tacoma. Email for more information.

If you are at Friday Harbor, you are currently not allowed to dispose of any chemical waste in the sink. Email for more information.

Please email if you have questions about disposal at other locations.

Dilution to meet the limits is not allowed

The concentration of your chemical after you have completed your activity determines whether or not you may sewer it. Your activity can include any equipment rinsing or any chemical treatment that you do as a normal part of cleaning up after an experiment. However, you may not dilute your chemical solely to meet sewer limits.

King County local sewer limits

This table outlines the King County sewer limits for specific common chemicals, plus temperature.

King County local sewer limits
Arsenic4.0 mg/L
Barium100 mg/L
Beryllium10 mg/L
Cadmium0.6 mg/L
Chromium5.0 mg/L
Copper8.0 mg/L
Cyanide3.0 mg/L
Lead4.0 mg/L
Mercury0.2 mg/L
Nickel5.0 mg/L
Selenium1.0 mg/L
Silver3.0 mg/L
Zinc10.0 mg/L
pH 5.5 - 12
Temperature150 F
Hydrogen sulfide10.0 mg/L
Fats, oil and grease (FOG)*100 mg/L
Settleable solids7 ml/L
Glutaraldehyde4% in water
Formaldehyde0.1% in water
Cidex OPA0.01% in water
Ethanol24% in water
Methanol10% in water
Isopropanol10% in water

* FOG includes fats, oils and grease from plant, animal, mineral, or petroleum sources.

Soaps and bleach

When you are washing glassware or equipment, you will likely use chemicals. The general rules and guidelines for washing with chemicals in the sink are:

  • Acetone may not go down the sink at any concentration. If you use acetone to rinse off items, you must collect any excess acetone in a securely capped, properly labeled waste container and dispose of it as hazardous waste (see the hazardous chemical waste page for more information.) You may not store acetone squeeze bottles near the sink.
  • Standard household bleach and other cleansers may go down the drain.
  • Do not use chromate based cleansers. There are many alternative cleansers that work just as well and are not as toxic.

Scintillation fluids

There is only one liquid scintillation cocktail product currently approved by the State of Washington Department of Ecology for disposal down the sanitary sewer. Other scintillation fluids may claim to be safer, but because they contain high concentrations of flammable surfactants, they are not approved for sewer disposal.