If your chemical is hazardous waste, it cannot be poured down the drain.
However, some dilute mixtures of chemicals can be poured down the drain. Refer to the following tables and rules for limits on some specific chemicals. These rules were designed to protect surface waters and biosolids from the wastewater treatment plant. Wastewater from King County goes to King County's West Point sewage treatment plant and then into the Puget Sound.
These rules apply only to UW Seattle, UW Bothell, and other sites within King County. If you are outside King County (UW Tacoma, Pack Forest, and Friday Harbor), you are not allowed to pour any chemicals down the drain. For more information, call EH&S at 206.685.3759 or email chmwaste@u.washington.edu
King County local sewer limits
This table outlines the King County sewer limits for specific common chemicals, plus temperature.
| King County local sewer limits |
| Chemical | Limit (mg/L) |
|---|
| Arsenic | 4.0 |
| Cadmium | 0.6 |
| Chromium | 5.0 |
| Copper | 8.0 |
| Cyanide | 3.0 |
| Lead | 4.0 |
| Mercury | 0.2 |
| Nickel | 5.0 |
| Silver | 3.0 |
| Zinc | 10.0 |
| pH | Between 5.5 and 12 |
| Temperature | 150 F |
| Hydrogen sulfide | 10.0 |
| Fats, oil and grease (FOG)* | 100 |
| Settleable solids | 7 ml/l |
* FOG includes fats, oils and grease from plant, animal, mineral, or petroleum sources.
King County additional guidelines
This table outlines additional limits for commonly used laboratory chemicals.
| Additional King County sewer guidelines |
| Chemical | Limit |
|---|
| Glutaraldehyde* | 1% in water |
| Formaldehyde | 0.1% in water |
| Ethanol | 24% in water |
| Methanol | 10% in water |
| Isopropanol | 10% in water |
| Barium | 100 mg/L |
| Beryllium | 10 mg/L |
| Selenium | 1.0 mg/L |
* Cold sterilant solutions containing no more than four percent glutaraldehyde may be discharged to the King County sanitary sewer provided appropriate BMPs are followed.
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 are only three liquid scintillation cocktail products currently approved by the State of Washington Department of Ecology for disposal down the sanitary sewer. They are soluble (or readily dispersible) in water and contain less than 10% non-ionic surfactants. Other scintillation fluids may claim to be safer, but because they contain high concentrations of flammable surfactants, they are not approved for sewer disposal.
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.
Sewer Discharge Log
All discharges must be recorded in a Sewer Discharge Log. The only exceptions to this rule are soaps and bleach. Identify the identity and concentration of waste, the volume discharged, the date of discharge, and your initials.
Keep a log posted near the sink; the emergency number on it must be posted in the event of an accidental release of chemicals to the sewer. Keep these logs for three years. County inspectors can ask and have asked to see Sewer Discharge Logs.
Click here for a blank Sewer Discharge Log (pdf).
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