Public Water Systems

A public water system is a water supply that serves more than one dwelling unit or a business.

This means that systems providing water to two or more homes, as well as most businesses, must meet higher standards than systems that serve only one home. As the number of people served or connections increases, so does the amount of requirements and level of oversight. The intent of this is to assure safe and reliable water to all users.

Public water supplies are divided into two categories based on the number of people they serve and/or connections.

1) Group A Systems

These are water supplies that regularly serve 15 or more residential connections, 25 or more people per day for 60 or more days per year, or 1000 people for two days or more per year. Group A systems are regulated by the Washington State Department of Health (WSDOH) under WAC 246-290. If you are interested in developing or revising a Group A system contact WSDOH at (360) 236-3030.

For information on Group A Systems see the Washington State Department of Health Drinking Water Program.

2) Group B Systems

These are water supplies that serve 2 to 14 service connections and fewer than 25 people per day or 25 or more people per day for less than 60 days per year. Group B systems are regulated by Lewis County Public Health & Social Services under Lewis County Code 8.55.

Group B water systems are subsequently divided by type and number of service connections:

Two service connections and/or a small business

More than two service connections or a facility which is used for an activity requiring a permit or a license


Two-Party Shared Well, Two Connection, or Small Business Water Supplies

Wells that serve two dwelling units or small businesses are by definition a Group B Water Supply. However, Lewis County Code 8.55 establishes reduced regulatory requirements for these types of water systems, LCC 8.55.020 (3). If the proposed water supply will serve two connections or less and does not provide water to 25 or more people per day, the following materials and information apply.

Lewis County’s Code 8.55 is intended to assure that two homes sharing a single well are each provided with a reasonable amount of healthful, potable water, both now and in the future. Upon approval, shared wells have conducted extensive testing to verify that the water does not pose a health risk and have established covenants to protect the well from becoming contaminated. In addition, the rights and responsibilities of each property owner are legally established regarding access to the well and water works, as well as water treatment, if applicable. Without these provisions, each party’s source of water is vulnerable to the whims of the other.

Without a Shared Well approval, problems often arise when properties once owned by family members or friends are sold and the new owners have different opinions regarding the system. For example, without a Water Users’ Agreement and established easements, the property containing the well is under no obligation to supply water to the second property.

Two-Party Shared well packets are available from Public Services or from the 3rd floor of the Health Department. You may also print out the documents from the link below.

Wells that Serve Two Connection Packet

Note: Ongoing bacteria and nitrate monitoring is not required for two-party wells at this time. However, it is strongly recommended to test for bacteria at least every year and for nitrate at least every three years. Systems with nitrate concentrations greater than 3.0 ppm should be tested more frequently.

*"Human consumption" means the use of water for drinking, bathing or showering, hand washing, food preparation, cooking, or oral hygiene. (source)