Drinking Water Quality


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Before your water is delivered to your tap, the City of Ann Arbor conducts many tests to ensure it is safe and healthy for you use. Below are the commonly asked about components of water quality. A full list of ingredients are published in the the Drinking Water Quality reports annually.


Turbidity, the measure of a liquid’s ability to scatter light, is often thought of as a measure of the particles in water or the cloudiness of water. Particles in water can be a variety of things, such as dirt, and may or may not have associated health risks. More particles in water cause examples of turbidity more light to be scattered when a light beam is passed through the water, which means higher turbidity. Turbidity naturally occurs in rivers, lakes and wells but is something that drinking water plants are required to remove.

Turbidity is used as a way to measure how well a treatment plant is operating. Well operated plants have low turbidity, and are unlikely to have other problems, such as with microorganisms, passing through the system. High turbidity indicates that a process is not working as well as it should. This does not necessarily mean there is health risk, but it is an indicator that actions need to be taken to improve water quality. Federal and State standards have recently changed to reduce the allowable amount of turbidity in drinking water and in the treatment processes used to produce that water. These new standards include more notification of the public when the treatment processes are not working optimally. 

Water Sodium Content

The City of Ann Arbor's drinking water averages 60 mg/l or ppm (parts per million). Most of this sodium is naturally occurring.

Water Hardness

Water hardness is a measure of dissolved minerals, specifically calcium and magnesium, in your water. These minerals are naturally occurring. The Ann Arbor Water Treatment Plant treats the water to reduce the hardness. How well this process works varies seasonally with the water temperature. In 2012 the average hardness of Ann Arbor water was 129 mg/l or parts per million (ppm), and is generally lower in the summer and higher in the winter.

Washing machine and dishwasher manufacturers often recommend settings based on grains/gallon (GPG) of water hardness scale. To convert mg/l or ppm to GPG, divide by 17.1. e.g. the hardness of Ann Arbor water could also be expressed as 7.54 GPG. Harder water requires more soap to form suds and provide effective cleaning.


mg/l or ppm


Less than 5.3

Less than 90




Moderately Hard




Over 10.5

Over 180

Very Hard


All Ann Arbor water samples collected and analyzed were well within strict Federal and State limits for lead in drinking water, based on data from the 2008 testing. Of 54 homes sampled, two exceeded the action level for lead.

If present, elevated levels of lead can cause serious health problems for pregnant women and young children. Here are some simple tips to help reduce lead in drinking water: 

  • Turn on your cold water faucet and run the tap for 30 seconds - 2 minutes before using water for drinking or cooking. Lead occurs in water when it has been unused in a home for an extended period (6+ hours) so, flush the water line in the morning and after work to avoid lead.
  • Use cool water for cooking and preparing baby formula. Hot water will leach lead, if this metal is present in the plumbing system.

Lead in drinking water is primarily from materials and components associated with service lines and home plumbing. The City of Ann Arbor cannot control the variety of materials used in plumbing components. If you are concerned about lead in your water, you may wish to have your water tested. Information on lead in drinking water, testing methods, and steps you can take to minimize exposure is available from the Safe Drinking Water Hotline (1-800-426-4791) or on the EPA's website​

White Particles

There are two types of white particles that have been observed in Ann Arbor drinking water. They have very different causes and solutions. Both occur rarely.

One type is calcium. The water pipes are naturally lined with a calcium deposit. When pressure changes occur, such as during plumbing work, water main breaks, hydrant flushing or other disruptive procedures, some of this calcium may break loose from the pipe and come out the water faucet. Typically, the particles will be very small, around 1 mm in diameter. They usually do not clog the aerators (screens) on faucets. They are very hard, but can be dissolved in vinegar. These are the same deposits that you may notice inside a teakettle after many uses. These types of particles should only occur for a very brief time. If they are persistent or abundant in the water, you should call the water plant so that we can investigate and take action.

The second type of particle is actually plastic. The particles vary in size, even up to half an inch. They are noted for plugging up aerators. They are white in appearance, but one side may be yellowish. They can be crumbled by hand and do not dissolve in vinegar. They will melt if placed in a flame (we do not recommend this, as they may also smell bad). Also, these particles float whereas the calcium particles described above do not. Often these particles are associated with a loss in hot water capacity. That is because they are actually parts of the hot water heater – specifically the dip tube. The dip tube is the tube that directs the cold water into the bottom of the tank for heating. Dip tubes manufactured from 1993 to 1996 are prone to this failure. The particles are non-toxic. The manufacturer should cover replacement of these dip tubes. The web site www.hotwater.com ​has more information.

Emerging Contaminants

Through grants from the Michigan Department of Natural Resources and the Environment (MDNRE) in 2004 and 2005, Ann Arbor conducted one of the nation's first comprehensive water testing of minute quantities of pharmaceuticals, personal care products, and endocrine-disrupting compounds in the city's drinking water. Most contaminants were either not detected or were found at very low levels in the Huron River. Most of the contaminants were removed or reduced by the drinking water treatment. Contaminants were found in the raw sewage. Variable removals were observed by the wastewater treatment process.