Where Does My Water Come From?

Where does my drinking water come from?

All the water we filter and process comes from either the Patuxent River or the Potomac River.

The source water treated at the Patuxent Water Filtration Plant comes from two reservoirs: the Triadelphia Reservoir and the T. Howard Duckett Reservoir, which is also known as Rocky Gorge. Water from those reservoirs is pumped to the filtration plant. The Potomac Water Filtration Plant draws water directly from the Potomac River.

This map shows the approximate areas served by both plants. Most of our service area in Montgomery County and a large portion of lower Prince George's County receive their water from the Potomac. The area of Prince George's County that surrounds Laurel receives its water from the Patuxent. The middle section of Prince George's County and a small southern portion of Montgomery County receive blended water, which is water from both the Patuxent and Potomac filtration plants.

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Is my water "hard" or "soft"?
That depends on which filtration plant provides your water. Water is considered to be "hard" if it contains more dissolved calcium and magnesium; Potomac River water tends to be hard (typically averaging about 120 to 130 milligrams of dissolved calcium and magnesium per liter) while Patuxent water is soft (typically averaging about 60 to 65 milligrams per liter).