New Hampshire county well guide

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

About 25,422 households in Merrimack County, 43% of the county, rely on a private well. Nobody tests that water unless the owner does.

Labs within 40 milesLicensed contractors
43%of households on a private well
Share on wells, county vs state
Merrimack County43%
New Hampshire average37%
17licensed contractors serve the county
<1 mito the nearest certified lab, New Hampshire DHHS Public Health Laboratories
Nostatewide test required when a home is sold

In Merrimack County, roughly 43% of households, about 25,422 homes, draw their water from a private well. Nobody tests it, treats it or inspects it unless the owner does.

Local rules for wells in Merrimack County

The rules that apply in Merrimack County are set at the state level in New Hampshire. The state does not require a test on a new well, and nothing is required at sale. Some counties and townships add permits or setbacks of their own, so check locally before drilling. The state's own recommendations are below.

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 Merrimack County

The nearest certified lab is New Hampshire DHHS Public Health Laboratories in Concord, in the county, and it accepts samples from homeowners. There are 7 more within 40 miles, listed below with what each tests for.

8 certified labs within 40 miles

Licensed well contractors serving Merrimack County

Licensed help in Merrimack County includes Barton Brothers LLC and C C Thomas & Sons LLC and 15 others. Every listing was matched to the New Hampshire license list; the "verify" link on each profile opens the state lookup.

Well depth and water chemistry

Well depth and water chemistry in Merrimack County follow the rock underneath it. Typical wells here run 240 to 480 feet; the median of 3,348 new domestic wells in the NHDES Water Well Inventory completed since 2000 is 360 feet. Contaminants worth testing for in this part of New Hampshire include 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.

Typical well depth

240 to 480 feet; the median of 3,348 new domestic wells in the NHDES Water Well Inventory completed since 2000 is 360 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: Belknap County, Hillsborough County, Rockingham County, Strafford County.

What well work costs in Merrimack 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 Merrimack County well owners ask

How many homes in Merrimack County are on a well?

About 25,422, or 43% 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 Merrimack County?

New Hampshire DHHS Public Health Laboratories in Concord, inside the county. It accepts homeowner samples.

Do I need a permit to drill a well in Merrimack 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 Merrimack 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.