Understanding Your Drinking Water

Water flowing to a well

More than 11.1 million people each day use tap water supplied by Ohio's public water systems. Many more use or benefit from Ohio's extensive ground water resources. Ohio EPA's Division of Drinking and Ground Waters participates in many activities to ensure Ohio's tap water is safe to drink and our precious water resources are protected for future generations.

Water is one of those things that people usually take for granted—until it is either gone or unsuitable to drink. Do you know where your drinking water comes from? Or how it is treated before it gets to your tap? The tabs below provide an understanding of your drinking water - from source to your faucet - along with some educational resources available through Ohio EPA.


Where Does Your Drinking Water Come From?

Hydrologic Cycle

Although water covers about 70 percent of the Earth, less than 1 percent is available as freshwater for human use. The vast majority of our water is found in the ocean, which is too salty to drink and unfit for many other applications. Of the freshwater available on Earth, about two-thirds is frozen in ice caps and glaciers, which leaves only a small fraction accessible for human use.

Ohio's drinking water comes from two primary sources: surface water and ground water. Surface water comes from lakes, reservoirs, rivers and streams. Groundwater is water underground in aquifers (highly permeable rocks, soil and sand), which can be extracted through wells or found as springs.

Sources of Ohio Drinking Water

Ground Water

What is Ground Water?

Artesian wellIn the most general case, ground water is simply water that exists below the land surface and fills the spaces (pores) between soils and sand grains or the cracks and crevices in rocks. If the earth material is capable of yielding usable quantities of ground water to a well or spring, it is called an aquifer. In most areas, ground water moves slowly (sometimes only a few feet per year).

There are two basic types of aquifers in Ohio: sand and gravel aquifers and bedrock aquifers. Ground water in sand and gravel aquifers occurs in pore spaces between individual grains of sand and gravel. In bedrock aquifers, ground water occurs in pore spaces and along fractures, joints, voids and contacts between different formations.

Where Does Ground Water Come From?

Rain and melted snow infiltrating through the soil column are the main sources of ground water. Much of the water entering the soil is used by plants. A small amount is held in the soil, and the rest moves downward to the aquifer. An aquifer has to be saturated (all pore spaces are filled with water) to allow water to flow to a well or stream. The top of the saturated zone is the water table. Between rainfall events, the ground water discharges to streams. In Ohio, it is typical for the water table to fluctuate a few feet between wet and dry seasons. Streams and lakes occur where the water table is at or above the ground surface.

For more information on ground water in Ohio, visit Ohio EPA's Ground Water Quality Characterization Program webpage.

Surface Water

What is Surface Water?

Stream samplingMore than half of Ohio's citizens get their drinking water from surface water sources. These include lakes, reservoirs, rivers and streams. Surface water is easier to obtain than ground water, but it is also more susceptible to contamination from nearby land uses. More treatment is required to ensure that the water is safe for consumption.

More information on surface water quality is available on Ohio EPA's Division of Surface Water home page and Ohio EPA's Public Drinking Water Supply Beneficial Use webpage.


How Does Public Drinking Water get to your Faucet?

Water treatment plantIn a typical community public water system, water is transported under pressure through a distribution network of buried pipes. Smaller pipes, called house service lines, are attached to the main water lines to bring water from the distribution network to your house.

In many community water systems, water pressure is provided by pumping water up into storage tanks that store water at higher elevations than the houses they serve. The force of gravity then "pushes" the water into your home when you turn on your tap.

Some water suppliers use treatment processes if it's necessary to remove contaminants from the drinking water. The most commonly used processes include filtration, flocculation, sedimentation and disinfection. If you want to know what types of treatment are used for your water supply, contact your local water supplier or public works department. 

More information about the drinking water treatment process is also available.


Educational Resources for Drinking and Ground Water

sand tank

Ohio's Source Water Environmental Education Teams (SWEETs) can give presentations at schools, public meetings, festivals or other local events on the importance of protecting your drinking water source. Check out the fact sheet to find the SWEET nearest to you.

Ohio EPA's Office of Environmental Education administers the Ohio Environmental Education Fund, awarding up to $1 million annually in grants for projects targeting preschool through university students and teachers, the general public and the regulated community. The Office also administers the Ohio Clean Diesel School Bus grant program and a scholarship program for university students in environmental science and engineering.

Other Educational Materials