New Hampshire county well guide

Well Water in Coos County, NH: Testing, Contractors and Rules

About 3,923 households in Coos County, 31% of the county, rely on a private well. Nobody tests that water unless the owner does.

Labs within 40 milesLicensed contractors
31%of households on a private well
Share on wells, county vs state
Coos County31%
New Hampshire average37%
3licensed contractors serve the county
40+ mito a certified lab; mail-in kits recommended
Nostatewide test required when a home is sold

Coos County has an estimated 3,923 households on private wells, 31% of the county. If you are one of them, testing, treatment and repairs are yours to arrange.

Local rules for wells in Coos County

Private wells in Coos County follow New Hampshire's statewide rules, administered by New Hampshire Water Well Board, staffed by the NHDES Drinking Water and Groundwater Bureau. No water test is required by the state 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 wellNot required statewide

No statewide water test and no state permit for a household well. The well must be constructed by a New Hampshire licensed water well contractor to the Water Well Board's rules (steel casing seated into bedrock or at least 20 ft, a watertight cap 12 inches above grade, and the setbacks in the subdivision and septic rules, 75 ft from a leach field for most lots), and the contractor files a well completion report with NHDES within 90 days, which puts the well in the state Water Well Inventory. Most towns require a bacteria test, and some a full Standard Analysis, before a certificate of occupancy; NHDES recommends the Standard Analysis on every new well before it is used.

Water test when a home is soldNot required statewide

No statewide requirement. RSA 477:4-c requires the seller to disclose the well's location, type, malfunctions and the date and results of the most recent water test, so buyers routinely test as a contingency, and FHA, VA and USDA loans require a bacteria, nitrate and lead sample from an accredited lab. Radon and arsenic are the results that most often hold up a New Hampshire closing.

What the state recommends

NHDES recommends the Standard Analysis every three to five years and bacteria and nitrate every year, plus a test after any well or plumbing work, flooding or a change in taste, color or smell. The Standard Analysis from the state lab covers bacteria, nitrate, nitrite, arsenic, uranium, fluoride, chloride, copper, iron, lead, manganese, sodium, hardness, pH and radon. New Hampshire uses its own arsenic standard of 5 ppb, half the federal limit, and NHDES also suggests a one-time PFAS test for wells in the southern tier and near known contamination.

Free or low-cost testingAvailable

No statewide free program. The NH Public Health Laboratories in Concord sell the Standard Analysis kit for a modest fee (the radon vial is a separate sample), picked up at the lab or mailed, and NHDES interprets the results through its Be Well Informed web tool. Towns and regional planning commissions periodically run subsidized arsenic and radon screening, and the state has paid for PFAS sampling of wells near known sources.

Getting your water tested near Coos County

No state-certified lab sits within 40 miles of the center of Coos County. That is common in rural New Hampshire, and the practical answer is a mail-in kit: the lab ships bottles, you sample at the kitchen tap and ship them back cold. The finder below widens the search to the whole state.

No listings yet for this area. Try widening your search.

Licensed well contractors serving Coos County

3 licensed contractors serve Coos County, including Arnold Pump and Colebrook Plumbing & Heating, Inc. 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 Coos County typically reach 220 to 440 feet; the median of 790 new domestic wells in the NHDES Water Well Inventory completed since 2000 is 320 feet. What comes up with the water depends on the aquifer, and across New Hampshire the usual suspects are arsenic (naturally occurring in bedrock, worst in the southeast from nashua and manchester to the seacoast, where about one well in five is over the state's 5 ppb standard), radon in water (granitic bedrock statewide. A first full panel tells you which of them apply to your well.

Typical well depth

220 to 440 feet; the median of 790 new domestic wells in the NHDES Water Well Inventory completed since 2000 is 320 feet

Contaminants to test for
  • Arsenic (naturally occurring in bedrock
  • Worst in the southeast from Nashua and Manchester to the Seacoast
  • Where about one well in five is over the state's 5 ppb standard)
  • Radon in water (granitic bedrock statewide
  • Highest in the Monadnock region and the southeast)
  • Uranium (granite in the same areas)
  • Manganese and iron (bedrock and overburden wells)
  • Fluoride (locally high in bedrock)
  • Coliform bacteria (dug wells and old drilled wells with shallow casing)
  • Hardness and sodium and chloride (road salt along the interstates and in the southern tier)
  • Nitrate (shallow wells near farms and septic-dense lots)
  • PFAS (southern Hillsborough and Rockingham counties near the Saint-Gobain plume in Merrimack
  • Bedford and Litchfield
  • And near the former Pease Air Force Base)

Neighboring counties: Carroll County, Grafton County, Belknap County, Merrimack County.

What well work costs in Coos County

Bacteria test (coliform and E. coli)$15published New Hampshire lab fees
Nitrate test$10 to $80varies by lab; ask when you order
Broad panel (metals and minerals)$85 to $90published New Hampshire lab fees
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

New Hampshire state lab: $15 bacteria, $85 standard analysis, $90 home buyer test. Installed costs are national 2026 ranges; local quotes vary with depth, access and materials. Sources, checked September 2026: NH Water Analysis Laboratory testing guide, HomeGuide cost guides, Angi: cost to shock a well.

Questions Coos County well owners ask

How many homes in Coos County are on a well?

About 3,923, or 31% 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 Coos County?

There is no certified lab within 40 miles. Use a mail-in kit from a New Hampshire certified lab, or the county health department if it collects samples.

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

No statewide water test and no state permit for a household well. The well must be constructed by a New Hampshire licensed water well contractor to the Water Well Board's rules (steel casing seated into bedrock or at least 20 ft, a watertight cap 12 inches above grade, and the setbacks in the subdivision and septic rules, 75 ft from a leach field for most lots), and the contractor files a well completion report with NHDES within 90 days, which puts the well in the state Water Well Inventory. Most towns require a bacteria test, and some a full Standard Analysis, before a certificate of occupancy; NHDES recommends the Standard Analysis on every new well before it is used.

What does a well test cost near Coos County?

Published lab fees in New Hampshire: $15 for a bacteria test. New Hampshire state lab: $15 bacteria, $85 standard analysis, $90 home buyer test. Mail-in kits cost about the same as walking in.