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Water Taste and Odor Problems

There are basically two causes of taste and associated odor problems. 

  1. A problem with Lake Oswego source water.
  2. An interaction of disinfection agents with a build-up of organic material in your homes plumbing system.

The first step to identifying and solving the problem is to determine whether the problem exists in the City's water supply or in your plumbing. If the problem occurs in only one or several, but not all, of the water faucets inside your home or business, the cause is somewhere in your plumbing system. If the problem is in the water supply, it will occur at every water faucet on the property. If the problem goes away after running the water for a few minutes, this will also determine that the cause is somewhere in your plumbing system. If it does not disappear after a few minutes of running the water please check the water supply to the property. 

To check the water supply, take a clean glass and go to the water faucet (hose bib) at the front of your house, apartment, or business. This faucet is usually near the main water shut-off valve for the property (commonly called the wheel valve). Turn the water on wide-open and run it for a full two minutes. Check your watch; two minutes is a long time. After two minutes, disconnect the water hose if there is one attached, and sample the water; never drink water that has traveled through a garden hose. With the passage of stricter water quality standards over the last several years, the City of Lake Oswego must add more chlorine to the water. The average person will likely be able to detect a slight to moderate chlorine taste and odor in the water supply.

If the taste or odor seems overpowering or bleachy at the front tap, contact the Water Treatment Plant at (503) 635-0394.  If the water is much better at the front faucet than at faucets inside your property, you should flush your plumbing system.

Sulfurous (rotten egg-like), decayed, or sewage-like taste or odor in the water

There are two common causes of a sulfurous, decayed, or sewage-like taste or odor in the water: bacteria growing in your drain or bacteria growing in your water heater. By far, the most common cause of this type of problem is the drain. Over time organic matter (such as hair, soap, and food waste) can accumulate on the walls of the drain. Bacteria can grow on these organic deposits. As the bacteria grow and multiply, they produce gases which often smell like rotten eggs or sewage. These gases accumulate in the drain until you turn the water on. As the water runs down the drain, the gases are expelled into the air around the sink. It is natural to assume the bad odor is coming from the water because you only smell it when you turn the water on. However there is nothing wrong with the water, you just need to disinfect the drain.

Another cause of a rotten egg or sewage smell in the water is bacteria growing in the water heater. This is most likely to occur if the hot water has been unused for a significant period of time, if the water heater has been turned off for a while, or if the thermostat on the heater is set too low. The bacteria that produce this problem are not a health threat; however, the taste and odor can be very unpleasant. This problem can be solved by heat disinfection of the water heater.

Musty, moldy, or earthy taste and odor in the water

There are two common causes of a musty, moldy, or earthy taste and odor in the water: bacteria growing in your drain, or certain types of organisms growing in the City's water supply. By far, the most common cause of this type of problem is the drain. Over time organic matter (such as hair, soap, and food waste) can accumulate on the walls of the drain.

Bacteria can grow on these organic deposits. As the bacteria grow and multiply, they produce gases which can smell musty or moldy. These gases accumulate in the drain until you turn the water on. As the water runs down the drain, the gases are expelled into the air around the sink. It is natural to assume the bad odor is coming from the water because you only smell it when you turn the water on. However, there is nothing wrong with the water, you just need to disinfect the drain.

You may notice a musty or earthy taste in the drinking water in the late Summer and early Fall. Due to low river and reservoir levels, warm water, and high nutrient content certain types of algae are in higher concentration in the river at the end of the summer. As these organisms grow and multiply, they excrete small amounts of harmless chemicals into the water that cause a musty, moldy, or earthy taste and odor. The two most common chemicals are geosmin and methylisoborneal (MIB). Although these chemicals are harmless, the human senses of taste and smell are extremely sensitive to them and can detect them in the water at extremely low concentrations.  Since 1995, the City and its water provider partners on the Clackamas River have participated with the United States Geological Service in a comprehensive program of monitoring for the presence of these and other organisms.  The water treatment plant staff adjust the treatment process to include powdered activated carbon that will absorb some of the odor causing compounds. This treatment process should improve the taste and odor of the water in a matter of a few days. If you have questions or concerns about the water, please contact the Water Treatment Plant at (503) 635-0394.