Water Department Online -  Water: From Its Source to Our Taps

Where does our water come from? How is it treated? How do we know it is safe to drink?

To answer these questions, it's important to go back to the basics. There are two main sources of water: surface water and groundwater. Surface Water is found in lakes, rivers, and reservoirs. Groundwater lies under the surface of the land, where it travels through and fills openings in the rocks. The rocks that store and transmit groundwater are called aquifers. Groundwater must be pumped from an aquifer to the earth's surface for use. Hopkinton's water supply is from groundwater sources.

Consumers receive their water from one of two sources: a private well, or a community water system. A household well pumps groundwater for household use. The source of a community water system may be either surface water or groundwater.

Private Household Wells

Approximately 15 percent of the U.S. population relies on individually owned and operated sources of drinking water, such as wells, cisterns, and springs. The majority of household wells are found in rural areas.

Those who receive their water from a private well are solely responsible for the safety of the water. Private wells are not subject to federal regulations, and are generally regulated on a very limited basis by states. Local health departments may assist well owners with periodic testing for bacteria or nitrates, but the bulk of the responsibility for caring for the well falls on the well owner.

Since the well owner is primarily responsible for the water, it is important to know what poses a threat to the well and the groundwater which is its source. A variety of sources can cause well water to become contaminated.

Several contaminants occur in nature that may present a health risk if they are found in drinking water. They include bacteria, viruses, uranium, radium, arsenic, and fluoride. Many of these contaminants are naturally present in rock formations, and consequently end up in the water supply.

Other sources of contamination are a result of human activity such as manufacturing or agriculture, or individual misuse. The following activities may cause harmful chemicals to enter the well water owner's water supply.

• Leakage from waste disposal, treatment, or storage sites.
• Discharges from factories, industrial sites, or sewage treatment facilities.
• Leaching from aerial or land application of pesticides and fertilizers on yards or fields.
• Accidental chemical spills.
• Leakage from underground storage tanks.
• Improper disposal of household wastes such as cleaning fluids, paint, and motor oil.

Well owners generally disinfect or otherwise treat the water from their wells to remove the contaminants that are caused by such activities.

Community Water Systems

Approximately 85 percent of the U.S. population receives its water from community water systems. Community water systems are required to meet the standards set by the U.S. Environmental Protection Agency (EPA) under the authority of the Safe Drinking Water Act (SDWA).

The SDWA was passed by Congress in 1974 to establish nationally consistent drinking water standards. A standard is the maximum level of a substance that the EPA has deemed acceptable in drinking water.

In 1986 the SDWA was amended to require the EPA to publish standards for 83 specific contaminants, and additional standards thereafter. To date, the EPA has issued or proposed limits for 87 substances. Community water systems are currently revising their drinking water programs to meet the more stringent requirements of the amendments.

Community water systems must ensure that the drinking water they supply does not have contaminant levels higher than the standards of the SDWA, the SDWA amendments, or state regulations.

In order to set a standard for a drinking water contaminant, the EPA first reviews the data concerning the health effects the substance may cause. The EPA then proposes nonmandatory Maximum Contaminant Level Goals (MCLG's). MCLG's are set at zero for contaminants that are known or probable human carcinogens. For noncarcinogens, MCLG's are set at a level where no adverse health effects would occur with a margin of safety.

At the same time, the EPA also proposes a Maximum Contaminant Level (MCL), the enforceable drinking water standard, which is set as close to the MCLG as possible, taking into account technological and economic considerations.

After a time for public comment and review of the MCL and MCLG, the EPA enacts a final regulation. States are expected to adopt the standard within 18 months of enactment.

The SDWA requires utilities to conduct routine monitoring and testing of public water supplies. Two types of sampling are required. Routine Sampling takes place on a regular basis and ensures that a treatment plant is running properly for delivering a consistent quality of drinking water. It also determines whether water quality meets the MCL's.

When a routine sample analysis indicates elevated levels of a particular contaminant that may exceed EPA or state standards, states may require systems to take a check sample. Check samples are used to confirm the results of a problem discovered during routine sampling.

The EPA generally delegates to the states the authority to enforce all federal drinking water standards, but can intercede when necessary. Sates must set standards that are no less stringent than the EPA's.

Point of Use Technologies

Whether consumers receive their water from a household well or a community water system, they may wish to treat it at its point-of-use (POU). Even water supplied by a community water system, which meets EPA standards, can generally benefit from POU treatment. Consumers have the option to choose the higher quality of water that POU technologies can provide.

POU technologies treat water at single or multiple taps or for the whole house, and improve water quality in a variety of ways. Unusual taste, color, and odor or water may be corrected by POU technologies, and some POU devices also reduce harmful contaminants.

One of the most popular POU technologies is water softening. An important characteristic of water is hardness, which is measured in grains per gallon (gpg). The more grains per gallon, the harder the water. The U.S. Geologic Survey reports that hard water is found in more than 85 percent of the United States. Hard water has many disadvantages. It can clog pipes and appliances, reduce clothing longevity by 15 percent, leave a soapy film on bathtubs and shower tiles, and increase water heating costs by nearly 30 percent while shortening the life of the heater. A water softener reduces the hardness of water, eliminating these problems and resulting in substantial savings.

Besides softening, a variety of POU equipment is available for improving drinking water and other special purposes. Each technology is designed to solve one or several different water quality problems. In order to choose the right equipment, it is important to confirm the nature and extent of the problem.

The first step in correcting a water quality problem is often to have the water tested. When the safety of the water is in question, it should always be tested by a state-certified or other reputable laboratory. Testing for aesthetic concerns such as taste, odor, color, and hardness may be performed in the home by a professional water treatment dealer.

Testing the water will help determine the proper treatment necessary. Before purchasing a product, become an educated consumer. Determine which contaminants the product reduces, and to what level. Also check the product's performance capabilities, maintenance provisions, and warranty. The Hopkinton water supply, as is most New England communities, is generally considered soft water.
Please see water quality page.

This article first appeared in the WaterReview Technical Brief, (1991) Volume 6, No. 3; a publication of the Water Quality Research Council. Copyright 1991, 1995 by the WQA. All rights reserved.