Montgomery County water quality report
Montgomery County is split among several suppliers, including Aqua Pennsylvania’s Main System, the North Wales Water Authority, and the North Penn Water Authority. Homes further north are often on private wells.
Moderately hard across most of the county, and very hard in the limestone belt through King of Prussia, Plymouth Meeting, and Whitemarsh.
What the Montgomery County reports show
Montgomery County water has 4 results over a legal limit in the latest reports.
Aqua Pennsylvania, Main System
Source: Aqua Pennsylvania, Main System, 2025 Water Quality Report
| What was measured | Result | Limit or guide | Status |
|---|---|---|---|
| Hardness | Not listed in this report. Utilities are not required to report hardness because it is not a health standard | No limit | For reference |
| PFOA | Highest result 13 ppt, range not detected to 13 | 14 ppt state limit, 4 ppt federal limit | Above federal limit |
| PFOS | Highest result 7.9 ppt, range not detected to 7.9 | 18 ppt state limit, 4 ppt federal limit | Above federal limit |
| Lead at customer taps | Not detected at the 90th percentile, highest 5.1 ppb, 0 of 60 homes above the action level | 15 ppb action level | Below limit |
| Total trihalomethanes | 29 ppb, range 0.9 to 70 | 80 ppb | Worth watching |
| Haloacetic acids | 20 ppb, range not detected to 45 | 60 ppb | Worth watching |
| Nitrate | 3.1 ppm, range 2 to 4.8 | 10 ppm | Below limit |
| Violations | Two paperwork violations in 2025 for late or incorrect reporting to the state, since corrected. No water quality limits were exceeded | n/a | For reference |
North Wales Water Authority
Source: North Wales Water Authority, 2025 Annual Water Quality Report
| What was measured | Result | Limit or guide | Status |
|---|---|---|---|
| Hardness | Not listed in this report. Utilities are not required to report hardness because it is not a health standard | No limit | For reference |
| PFOA | Running average 1.9 ppt from the Forest Park plant, 12.6 ppt from the North Wales wells | 14 ppt state limit, 4 ppt federal limit | Above federal limit |
| PFOS | Running average 10.5 ppt from the North Wales wells | 18 ppt state limit, 4 ppt federal limit | Above federal limit |
| Lead at customer taps | 1.6 ppb at the 90th percentile, 0 of 34 homes above the action level | 15 ppb action level | Below limit |
| Total trihalomethanes | 46.2 ppb, range 8.7 to 78.1 | 80 ppb | Worth watching |
| Haloacetic acids | 29.6 ppb, range 0 to 34.5 | 60 ppb | Below limit |
| Nitrate | 0.605 ppm Forest Park, 3.72 ppm North Wales wells | 10 ppm | Below limit |
Montgomery County hardness, U.S. Geological Survey
Source: Montgomery County hardness, U.S. Geological Survey, U.S. Geological Survey, Compilation of Ground-Water-Quality Data in Pennsylvania, Open-File Report 84-706, with rock type measurements from Water-Resources Investigations Report 77-67
| What was measured | Result | Limit or guide | Status |
|---|---|---|---|
| Hardness | Moderately hard across most of the county, and very hard in the limestone belt through King of Prussia, Plymouth Meeting, and Whitemarsh | Over 180 mg/L is very hard | Worth watching |
How to read a water quality report
Federal law requires every community water system to publish a report, often called a Consumer Confidence Report, by July 1 each year. It lists what the utility found in its water and how those results compare with safety limits.
A report describes water as it leaves the treatment plant and travels through the main pipes. It cannot tell you about the plumbing inside your home, which is where lead and copper usually come from. Private wells have no report at all, so testing is up to the owner.
| Term | What it means |
|---|---|
| MCL | Maximum contaminant level, the legal limit for drinking water |
| MCLG | The goal level with no known health risk. Often lower than the legal limit |
| Action level | For lead and copper, the level that requires a utility to take extra steps if more than 10% of homes tested exceed it |
| 90th percentile | Nine out of ten homes tested were at or below this number |
| Running average | An average of recent quarters. Many limits are judged this way, so one high sample is not a violation on its own |
| ppm, ppb, ppt | Parts per million, billion, and trillion. One ppt is like one drop in about 20 Olympic swimming pools |
| ND | Not detected at the lab’s reporting level |
Pennsylvania limits for PFOA and PFOS are 14 and 18 parts per trillion. The EPA has also set a 4 part per trillion limit for each, with a later compliance date.
How we tag results
| Result | When we flag it |
|---|---|
| PFOA and PFOS | Above federal limit when the result is over the EPA’s 4 ppt limit. Utilities have until 2031 to meet it, so this is not a violation yet. Worth watching when only individual samples are over 4 ppt |
| Disinfection byproducts | Worth watching when any result reaches 75% of the limit |
| Lead | Worth watching when any home tested is above the action level or the 90th percentile is above 5 ppb. There is no known safe level of lead for children |
| Nitrate | Worth watching above 5 ppm, half the limit |
| Sodium | Worth watching above the 20 mg/L guide for people on low sodium diets |
| Hardness | Worth watching above 120 ppm, where water is considered hard |
| Above limit | A violation or a result over the legal limit in the report |
On a well? There is no report for you
Pennsylvania does not regulate private wells, so nobody publishes results for your water. Public water reports describe public systems only.
Our guide to testing your private well in Pennsylvania covers what to test for, how often, and how to read the results.
Not sure what your report means for your home?
Bring it to a free consultation. We will walk you through every line and tell you honestly whether treatment is worth it.
Results summarized from each utility’s most recent published annual water quality report. Utilities update their reports every year, and results at your tap can differ from system averages. Last reviewed October 2026.
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