Water Aesthetics

The common water aesthetics concerns addressed below involve tastes and odors, including chlorine, and water stains and algae.

Taste & 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 problems.

Common taste and odor complaints are answered below.

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.


Water Stains

Pink, pinkish-orange or black rings

These may form around sink fixtures, drains, dog bowls and other standing containers of water and at the waterline of toilets. They are usually easily removed with cleaning and consist of a mixed culture of yeast, mold, and/or bacteria which grow well in moist conditions. To reduce the occurrence, you may just need to clean more often, especially in the summer when humidity and warmer temperatures increase microbial growth rates.

Reddish or orange staining

Orange stains on fixtures that are harder to remove are usually due to galvanized iron plumbing. Fixing the leaking faucet or more frequent cleaning should help the problem. Worn surfaces on old tubs and sinks require a lot of elbow grease to clean. There are rust removal compounds on the market, but care is needed to prevent damage to the finish of porcelain fixtures.



Seattle's water supply is extremely well protected from contamination. The water supplied by Seattle Public Utilities meets all current drinking water standards and is safe to drink. The Cedar River source water, and to a lesser extent on the Tolt, do experience naturally occurring, seasonal algae blooms. Typically the blooms occur in the late spring, but due to a number of environmental factors such as sunlight and temperature, blooms can occur at unexpected times of the year. For similar reasons some blooms are more intense than others. Although the algae we see in our supplies are not associated with health concerns, they can create tastes and odors. These are well controlled with current ozone treatment.

Filter clogging

Since the Cedar supply is unfiltered, customers who filter water at home may experience their filters clogging sooner than usual during an algal bloom. Your filter may appear to be covered with clay or plaster. To help alleviate filter clogging, an inexpensive pre-filter can be installed and periodically removed, cleaned with a brush or just replaced with a new one.


Public Utilities

Andrew Lee, General Manager and CEO
Address: 700 5th Avenue, Suite 4900, Seattle, WA, 98104
Mailing Address: PO Box 34018, Seattle, WA, 98124-5177
Phone: (206) 684-3000

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Seattle Public Utilities (SPU) is comprised of three major direct-service providing utilities: the Water Utility, the Drainage and Wastewater Utility, and the Solid Waste Utility.