2025 Tap Water Analysis Report

Patuxent Water Filtration Plant

Potomac Water Filtration Plant

Distribution System

Key

ND - not detected

mg/L - milligrams per liter, equal to parts per million (ppm). The equivalent of one minute in 2 years or one penny in $10,000.

μg/L - micrograms per liter, equal to parts per billion (ppb). The equivalent of one minute in 2,000 years or one penny in $10 million.

ng/L - nanograms per liter, equal to parts per trillion (ppt). The equivalent of one minute in 2,000,000 years or one penny in $10 billion.

pg/L - picograms per liter, equal to parts per quadrillion (ppq). The equivalent of one minute in 2,000,000,000 years or one penny in $10 trillion.

pCi/L - picocuries per liter (a measure of radiation)

S.U. - Standard Unit

NTU - Nephelometric Turbidity Unit

TT - Treatment Technique. A required process intended to reduce the level of a contaminant in drinking water.

AL - Action level. The concentration of a contaminant which, if exceeded, triggers treatment or other requirements which a water system must follow.

= equals

> greater than

< less than

Endnotes
 

¹ Filtered water, maximum of measurements taken every 15 minutes.

² EPA considers 50 pCi/L to be the level of concern for beta particles.

³ The EPA limit of 5 pCi/L applies to combined Radium 226 and 228.

⁴ If more than 10% of sites exceed action level, system is required to take additional steps to control corrosiveness of their water.

⁵All samples deemed to have detectable disinfectant residual.

⁶ Maximum residual disinfectant level (MRDL), the highest level of a disinfectant allowed in drinking water; based on RAA.

⁷ Highest locational running annual average (LRAA).

⁸ Maximum contaminant level based on LRAA.

⁹ Shown as maximum contaminant levels (MCL) unless otherwise noted as secondary MCLs (SMCL). MCLs are enforceable health-based standards, whereas SMCLs are non-enforceable guidelines for contaminants that may cause aesthetic effects in drinking water.