Well water in Montgomery County, Pennsylvania
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Testing strongly recommended
private wells tested between 2007 and 2025 in Montgomery County had total coliform above the EPA limit (0 MPN/100mL), according to the Penn State water testing lab.
519 private wells tested 2007 to 2025 in state summaries; 1,483 test results across 15 contaminants from at least 123 wells, 1925 to 2024; nitrate has the most at 258. Data refreshed September 16, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
These are samples homeowners paid to send to the Penn State lab, often because of a suspected problem, so shares above the limit run higher than a random survey would find.
An estimated 163,088 people in Montgomery County get their drinking water from a private well, per USGS 2015 county water use. That is about 20% of residents.
Separately, the USGS national arsenic model estimates that 3% of the 163,088 people on private wells in Montgomery County draw water above 10 ug/L (the model's range is 2% to 4%), from geology and well depth rather than local tests.
What homeowner tests found
Penn State Agricultural Analytical Services Lab drinking water summaries: private wells tested and reported to the state, 2007 to 2025. Shares are against the level the state applies to each contaminant, named in the last column; several are stricter than EPA.
| Contaminant | Above state level | Wells tested | Median | 95th pct | Highest | State level |
|---|---|---|---|---|---|---|
| Total coliform | 519 | 276 | 0 MPN/100mL | |||
| Arsenic | 162 | 109 | 10 ug/L | |||
| Lead (first draw) | 168 | 79 | 15 ug/L | |||
| Iron | 241 | 100 | 4,600 | 300 ug/L | ||
| E. coli | 519 | 201 | 0 MPN/100mL | |||
| Manganese | 238 | 10 | 2,860 | 50 ug/L | ||
| Chloride | 53 | 74.9 | 334 | 250 mg/L | ||
| Nitrate + nitrite as N | 168 | 2.8 | 13.4 | 10 mg/L | ||
| Copper | 302 | 0.02 | 1.49 | 1.3 mg/L | ||
| Sodium | 29 | 19.7 | 206 |
What individual samples found
Each row summarizes every public sample for that contaminant inside Montgomery County. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.
| Contaminant | Above limit | Samples | Detected | Median | Highest | Limit |
|---|---|---|---|---|---|---|
| Nitrate 1925 to 2024 | 258 | 98% | 4.08 | 59.6 | 10 mg/L EPA limit | |
| Arsenic 1979 to 2024 | 84 | 73% | 2 | 31 | 10 ug/L EPA limit | |
| Fluoride 1949 to 2024 | 150 | 57% | 0.04 | 6.51 | 4 mg/L EPA limit | |
| Uranium 1986 to 2024 | 86 | 85% | 2.92 | 64.8 | 30 ug/L EPA limit | |
| Lead 1974 to 2024 | 100 | 70% | 0.226 | 6 | 15 ug/L EPA limit | |
| Copper 1974 to 2024 | 82 | 89% | 0.006 | 0.138 | 1.3 mg/L EPA limit | |
| Radium (226 + 228) 1986 to 1999 | 32 | 75% | 0 | 1 | 5 pCi/L EPA limit | |
| E. coli 2000 to 2021 | 16 | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Chloride 1925 to 2024 | no limit | 160 | 100% | 22 | 446 | 250 mg/L nuisance level |
| Iron 1925 to 2024 | no limit | 158 | 73% | 14.1 | 17,000 | 300 ug/L nuisance level |
| Sodium 1925 to 2024 | no limit | 142 | 100% | 15 | 171 | 20 mg/L health guideline |
| Manganese 1956 to 2024 | no limit | 135 | 73% | 0.53 | 4,190 | 300 ug/L health guideline |
| Radon 1986 to 2024 | no limit | 66 | 100% | 1,755 | 5,080 | 2,000 pCi/L health guideline |
Sampled fewer than 10 times, too few to summarize: PFOA (7), PFOS (7).
Over time
Share of samples above the limit by period. A cell needs ten samples to show; a comparison needs twenty in each period. Later periods sample fewer wells, and often the ones already known to have a problem.
| Contaminant | before 2000 | 2000s | 2010s | 2020s |
|---|---|---|---|---|
| Nitrate | 23%154 samples | 20%60 samples | 21%24 samples | 20%20 samples |
| Fluoride | 0%99 samples | 7%28 samples | 0%12 samples | 0%11 samples |
| Lead | 0%52 samples | 0%25 samples | 0%12 samples | 0%11 samples |
| Uranium | 0%38 samples | 0%25 samples | 0%12 samples | 9%11 samples |
| Arsenic | 3%33 samples | 36%28 samples | 17%12 samples | 18%11 samples |
| Copper | 0%34 samples | 0%25 samples | 0%12 samples | 0%11 samples |
Fluoride above the limit in Montgomery County rose from 0% of 99 samples before 2000 to 7% of 28 in the 2000s.
Arsenic above the limit in Montgomery County rose from 3% of 33 samples before 2000 to 36% of 28 in the 2000s.
Nitrate, lead, uranium, copper have held within a few points between the two most recent periods with enough samples.
Closer than the county
See the sampled wells near your address
The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.
Check my addressWhat this means
Among homeowners in Montgomery County who sent a sample to the state lab, the health-based limits most often exceeded were total coliform (36% of 519 wells), arsenic (12% of 162 wells), and lead (10% of 168 wells). These are ordinary wells tested by their owners, so the shares are the best available picture of a typical well here, with one caveat: people test more often when they suspect a problem.
What to test for in Montgomery County
- 1Total coliform36% of 519 local wells tested were above the EPA limit.
- 2Nitrate22% of 258 local samples were above the limit.
- 3Arsenic18% of 84 local samples were above the limit.
- 4Lead10% of 168 local wells tested were above the EPA limit.
- 5E. coli5% of 519 local wells tested were above the EPA limit.
- 6Fluoride1% of 150 local samples were above the limit.
- 7Uranium1% of 86 local samples were above the limit.
- 8Copper<1% of 302 local wells tested were above the EPA limit.
Test your Montgomery County well for total coliform, nitrate and arsenic
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
Order the Tap Score well water test kit, from $209Already tested? Upload the report
Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.
Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.
Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.
Where to get a well tested in Pennsylvania: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Montgomery County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
Wells in Montgomery County
7,972 domestic wells in Montgomery County are on record with the state. 99% are drilled into bedrock, and the typical well is 182 feet deep (one in ten goes past 397 feet).
In a typical Montgomery County well, bedrock starts about 18 feet down, the median yield is 18 gallons per minute, 6% of wells yield under 3 gallons per minute and usually need a storage tank.
Bedrock wells are where arsenic, uranium and radon come from: the water sits in fractures in granite and metamorphic rock and picks up whatever the rock carries. That is why testing for those three matters more here than in a dug or gravel well.
Find your own well's report
The state keeps the driller's report for most wells drilled since 1984. It tells you how deep your well is, where bedrock starts, and how much water it makes, which decides what treatment can work.
- Open PaGWIS (Pennsylvania Geological Survey) and choose Water Well.
- The record lists depth, depth to bedrock, yield and use; drillers have reported new wells to the state since 1966.
Pennsylvania has no private well construction standard and does not require testing, so many older wells have no record at all.
The rock under Montgomery County
Early Mesozoic basin aquifers
Sandstone. Sandstone wells draw from pore space in the rock and tend to be dependable. Iron, manganese and hardness are common, and some sandstones carry arsenic or radium, so a first test should include both.
Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the county centroid. A single well can sit in a different unit, especially near a boundary.
Official help in Pennsylvania
Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.
- Private Wells, PA DEP
- Laboratory Accreditation Program, PA DEP
Treatment that fits the local profile
Total coliform
Inspect and repair the well cap and casing, then shock chlorinate and retest; UV disinfection whole-house; Chlorination system
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Lead
Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching
Iron
Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
Fluoride
Point-of-use reverse osmosis; Activated alumina; Distillation
Systems we would look at first
Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
For total coliform
Aquasana Rhino Well Water with UV
whole-house, at the point of entry, about $2,871
Whole-house system built for wells: sediment pre-filter, KDF and carbon, and a UV lamp rated to kill 99.99% of bacteria and viruses. It does not remove arsenic, nitrate, uranium or radon.
For arsenic
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For arsenic
Whole-house arsenic and uranium filter
whole-house, at the point of entry, about $2,500
Adsorptive iron-based media; sized to your well yield.
For arsenic
Aquasana SmartFlow reverse osmosis
under-sink or countertop, about $225
Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.
For lead
Aquasana Claryum 3-Stage under-sink filter
under-sink or countertop, about $175
Certified to NSF/ANSI 53 to reduce 99% of lead and 99.7% of PFOA and PFOS at the tap. Not a fix for arsenic, nitrate or bacteria.
For lead
Acid neutralizing filter
whole-house, at the point of entry, about $1,200
Raises pH so plumbing stops leaching lead and copper.
Free, no obligation
Get on the list for a free in-home water test in Montgomery County
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Common questions
How deep are wells in Montgomery County?
The typical domestic well in Montgomery County is 182 feet deep, based on 7,972 wells reported to the state. One in ten is deeper than 397 feet. 99% are drilled into bedrock.
Is there arsenic in well water in Montgomery County?
Arsenic was detected in 73% of 84 public well samples in Montgomery County, and 18% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.
How high is radon in well water in Montgomery County?
The median radon level across 66 public samples in Montgomery County was 1,755 pCi/L, with a high of 5,080 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Montgomery County?
Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.
Towns in Montgomery County
60 towns have fewer than 30 public samples and are included in the Montgomery County totals above rather than shown separately: Abington township, Ambler borough, Bridgeport borough, Bryn Athyn borough, Cheltenham township, Collegeville borough, Conshohocken borough, Douglass township, East Greenville borough, East Norriton township, Franconia township, Green Lane borough, Hatfield borough, Hatfield township, Horsham township, Jenkintown borough, Lansdale borough, Limerick township, Lower Frederick township, Lower Gwynedd township, Lower Merion township, Lower Moreland township, Lower Pottsgrove township, Lower Salford township, Marlborough township, Montgomery township, Narberth borough, New Hanover township, Norristown borough, North Wales borough, Pennsburg borough, Perkiomen township, Plymouth township, Pottstown borough, Red Hill borough, Rockledge borough, Royersford borough, Salford township, Schwenksville borough, Skippack township, Souderton borough, Springfield township, Telford borough, Towamencin township, Trappe borough, Upper Dublin township, Upper Frederick township, Upper Gwynedd township, Upper Hanover township, Upper Merion township, Upper Moreland township, Upper Pottsgrove township, Upper Providence township, Upper Salford township, West Conshohocken borough, West Norriton township, West Pottsgrove township, Whitemarsh township, Whitpain township, Worcester township.
Counties near Montgomery County
Closest first. Groundwater does not stop at a line on a map, so the next county over is a fair second opinion.
Want the numbers themselves? Download the Pennsylvania dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 1,483 samples in Montgomery County. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- Penn State Agricultural Analytical Services Lab drinking water summaries: summaries for 10 contaminants in Montgomery County, up to 519 wells each. County summaries of private water samples tested by the Penn State Agricultural Analytical Services Laboratory since 2007, published by the College of Agricultural Sciences. Counts are samples, not distinct wells. Shares are against the standard the lab prints: the EPA maximum contaminant level, or the secondary standard for iron, manganese and chloride. Lead is the first-draw result. Medians printed as 0.00 are stored as null because the lab rounds to two decimals. Retrieved September 16, 2026.
- USGS national arsenic model (Ayotte 2017): estimated share of 163,088 people on private wells in Montgomery County above 10 ug/L of arsenic, from geology, well depth and land use. County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018). Retrieved September 15, 2026.
- Pennsylvania Groundwater Information System (PaGWIS) wells: 17,625 well records in Montgomery County, 7,972 domestic. Water well records from the Pennsylvania Groundwater Information System, Pennsylvania Geological Survey (DCNR). Only aggregates are shown; owner names and addresses are never stored. Retrieved September 16, 2026.
Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.