Private Well Water Testing in Washington

County-by-county USGS area-risk estimates for private wells across Washington — arsenic exceedance probability and private-well population — plus how to test your own well at a Washington-certified laboratory.

Washington private-well risk summary

Counties covered

Washington counties with modeled risk data.

People on private wells

area estimate

683,988

estimated across covered Washington counties.

Average arsenic risk

area estimate

11%

average modeled chance a well exceeds 10 µg/L arsenic across covered counties.

Washington counties

Find a Washington-certified testing lab

Get your well tested at a Washington-certified laboratory. We list certification programs by state.

Washington certified labs

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Upload your well water lab report (PDF or a photo) and our team will email you a full, plain-English reading of every result — free. Educational only, never medical advice.

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These figures are USGS area estimates: statistical groundwater models describing how likely elevated contaminant levels are across a county. They are not designed to predict the concentration in any single well. Only testing your own well reveals its water quality.

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By TapWaterData Editorial