Missouri county well guide

Well Water in Washington County, MO: Testing, Contractors and Rules

About 7,123 households in Washington County, 72% of the county, rely on a private well. Nobody tests that water unless the owner does.

Labs within 40 milesLicensed contractors
72%of households on a private well
Share on wells, county vs state
Washington County72%
Missouri average14%
20licensed contractors serve the county
35 mito the nearest certified lab, Franklin County Lab
Nostatewide test required when a home is sold

Most homes in Washington County are on a private well: about 7,123 households, 72% of the county. That makes Washington County one of the places in Missouri where the water department is the homeowner.

Local rules for wells in Washington County

Private wells in Washington County follow Missouri's statewide rules, administered by Missouri Geological Survey, Well Installation Section, in the Department of Natural Resources. A water test is required when a new well is completed. There is no statewide test requirement when a home is sold, though lenders often ask for one. The cards below show the details and the official sources.

At a glance

Water test for a new wellRequired

No permit for the owner, but the well must be built by a Missouri permitted well installation contractor to the 10 CSR 23-3 standards for its drilling area (Missouri has 13 drilling areas with different minimum casing depths, grouted casing, 50 ft from a septic tank and 100 ft from a lagoon or drainfield), and the contractor must disinfect the well, take a water sample for bacteria after construction and file a well certification report with the Missouri Geological Survey within 60 days. The State Public Health Laboratory's New Well Series (pH, fluoride, chloride, nitrate, sulfate, iron, manganese and lead) is the usual chemistry check on a new well.

Water test when a home is soldNot required statewide

No statewide requirement. The Missouri seller's disclosure asks only whether the water supply is a private well and whether the seller knows of problems. FHA, VA and USDA loans normally require a bacteria, nitrate and lead sample from a certified lab before closing.

What the state recommends

The Department of Health and Senior Services recommends testing a private well every year for coliform bacteria, and every few years for nitrate, pH, hardness, iron, manganese, lead and copper (the State Public Health Laboratory's minerals, nutrients and metals panel covers all of these plus arsenic and uranium). Add radon and radium in the Ozarks, lead and cadmium in the Old Lead Belt and Viburnum Trend mining districts, sulfate and chloride in deep northern wells, pesticides in shallow Bootheel wells, and test again after flooding, well work or a change in taste, color or smell. Karst wells and springs in the Ozarks should be retested after heavy rain.

Free or low-cost testingAvailable

No free program, but the cheapest state lab in the country: the State Public Health Laboratory tests a private well or cistern sample for total coliform and E. coli for a $10 handling fee. Pick up the kit from your local public health agency or district health office, collect the sample and hand it back for the lab's free statewide overnight courier. Chemistry panels cost more and are ordered through the same agency or the Bureau of Environmental Epidemiology (573-751-6102).

Getting your water tested near Washington County

2 certified labs within 40 miles serve Washington County, starting with Franklin County Lab in Union (about 35 miles from the county center). Each card below shows whether the lab takes homeowner samples and which tests it is certified for.

2 certified labs within 40 miles

Licensed well contractors serving Washington County

20 licensed contractors serve Washington County, including A&M Pump Inc and Brute LLC. Each profile carries the state license number and the date we checked it, and the filters below sort them by drilling, pump work or treatment.

Well depth and water chemistry

Wells in Washington County typically reach 190 to 320 feet; the median of 1,844 domestic wells certified to the Missouri Geological Survey since 2000 is 240 feet. What comes up with the water depends on the aquifer, and across Missouri the usual suspects are coliform bacteria (the most common failure statewide, worst in ozark karst wells and springs after rain), nitrate (shallow wells in farm country, the bootheel and northern missouri). A first full panel tells you which of them apply to your well.

Typical well depth

190 to 320 feet; the median of 1,844 domestic wells certified to the Missouri Geological Survey since 2000 is 240 feet

Contaminants to test for
  • Coliform bacteria (the most common failure statewide
  • Worst in Ozark karst wells and springs after rain)
  • Nitrate (shallow wells in farm country
  • The Bootheel and northern Missouri)
  • Hardness (dolomite across the Ozarks)
  • Iron and manganese (glacial till
  • Alluvium and Bootheel sands)
  • Radon and radium (locally in the Ozark aquifer)
  • Lead
  • Cadmium and zinc (Old Lead Belt
  • Viburnum Trend and Tri-State mining districts)
  • Sulfate
  • Chloride and sodium (deep bedrock wells in northern and western Missouri)
  • Arsenic (locally)
  • Pesticides (shallow Bootheel and river-bottom wells)
  • PFAS near airfields and industrial sites

Neighboring counties: St. Francois County, Iron County, Crawford County, Jefferson County.

What well work costs in Washington County

Bacteria test (coliform and E. coli)$10published Missouri lab fees
Nitrate test$10 to $80varies by lab; ask when you order
Broad panel (metals and minerals)$85 to $450state and university lab packages
Well inspection$250 to $550$350 to $900 with water testing
Submersible pump replacement$1,000 to $2,500installed; deep wells cost more
Pressure tank replacement$800 to $1,500installed
One treatment unit$700 to $3,500softener, iron filter or UV, installed
Multi-stage whole-house treatment$2,500 to $10,000+several units or whole-house RO, installed
New well, complete$6,000 to $16,000typical 200 ft well with pump; drilling alone about $20 to $30 per foot; deeper wells cost more
Shock chlorination$80 to $200by a contractor; under $30 to do yourself

State Public Health Laboratory bacteria kit from any local health department ($10 handling fee). Installed costs are national 2026 ranges; local quotes vary with depth, access and materials. Sources, checked September 2026: Missouri State Public Health Laboratory, HomeGuide cost guides, Angi: cost to shock a well.

Questions Washington County well owners ask

How many homes in Washington County are on a well?

About 7,123, or 72% of households, based on Census housing data and state well surveys. The share is highest outside the towns with public water.

Where is the closest certified lab to Washington County?

Franklin County Lab in Union, about 35 miles away. It accepts homeowner samples.

Do I need a permit to drill a well in Washington County?

No permit for the owner, but the well must be built by a Missouri permitted well installation contractor to the 10 CSR 23-3 standards for its drilling area (Missouri has 13 drilling areas with different minimum casing depths, grouted casing, 50 ft from a septic tank and 100 ft from a lagoon or drainfield), and the contractor must disinfect the well, take a water sample for bacteria after construction and file a well certification report with the Missouri Geological Survey within 60 days. The State Public Health Laboratory's New Well Series (pH, fluoride, chloride, nitrate, sulfate, iron, manganese and lead) is the usual chemistry check on a new well.

What does a well test cost near Washington County?

Published lab fees in Missouri: $10 for a bacteria test. State Public Health Laboratory bacteria kit from any local health department ($10 handling fee). Mail-in kits cost about the same as walking in.