Taste and Odor

Seattle Public Utilities closely monitors all taste and odor problems reported, in addition to performing flavor profile analyses on a regular basis. Flavor profile analysis uses a group of trained panelists to identify flavors and/or aromas in raw and treated waters.

Both the Cedar Water Treatment Facility and Tolt Water Treatment Facility include ozonation. This treatment process has demonstrated outstanding effectiveness in reducing taste and odor (T&O) problems.

Common taste and odor complaints

Earthy or musty taste or odor

Now that all the in-town open reservoirs are covered, earthy or musty tastes in the water should not be an issue. Algae blooms still occur in our raw water reservoirs, but ozone treatment for both surface water sources is very effective at reducing any issues.

If a problem does occur, the best way to reduce the earthy or stale taste and odor is to flush the faucet for a couple of minutes. Then collect this freshened water into a clean container suitable for beverages, cover or cap it, and store it in the refrigerator for future drinking and cooking purposes. A few drops of lemon juice or a slice of lemon can also help improve the taste. If the taste and odor is still present, you may want to consider a home filter.

Plastic taste and odor

There are several possible sources of plastic taste and odor issues. One is from plastic pipes used for building plumbing. When water has sat stagnant in the plastic pipes, it may absorb some of the odor from the piping. To help alleviate the problem, flush the pipes before using the water for drinking or cooking.

Another source of plastic taste and odor is from our source water. Occasionally, source water algae blooms occur in our supply reservoirs. When this water is treated with ozone and chlorine at our treatment plants, the resultant taste and odor can seem somewhat plastic or vinyl like. Flushing will not alleviate this problem, but the suggestions listed above for earthy/musty taste and odor may help.


Our drinking water is treated with chlorine in order to protect against microbial contaminants. Because there is little else in our water that produces a taste or odor, the chlorine is often the only taste remaining. We try to add just enough chlorine so that it is still detectable at the end of the system. Most times, the chlorine leaving our treatment plants is 1.5 mg/L, and the average chlorine concentration in the distribution system is 0.8 mg/L. This is well below the maximum concentration allowed in drinking water, which is 4.0 mg/L.

Chlorine taste and odor can be minimized by either letting water sit overnight, or using a carbon filter. To let the water sit overnight, collect a fresh sample in a clean container suitable for beverages, loosely cover or cap it, and store it in either the refrigerator or on the counter. Carbon filters are very common in either a pitcher or faucet device. It is best to use a filter that has been NSF certified for removal of chlorine.

Links to other sites

NSF International