Guide · Updated September 5, 2026

Radon in Pennsylvania Well Water

Radon does not rust a Pennsylvania sink. It does not smell like a bad anode. The glass can look ordinary while a certified lab still prints picocuries per liter on a water sheet. People mix that line up with the indoor-air number they already know. EPA’s radon hub gives an action guideline of 4 pCi/L for indoor air. That is air. It is not a well-water limit, and it is not a score this site will turn into a health lecture.

Pennsylvania DEP does not regulate private wells the way it regulates a community system. EPA’s private-wells pages and CDC’s well-testing guidance say the owner is the utility. This page does not interpret a lab number as a medical result, does not design a treatment train, and does not rank a brand.

Get a certified-lab radon-in-water result first

Start at this site’s Pennsylvania certified-lab inventory. DEP’s Laboratory Accreditation Program search is the live list for drinking-water analytes such as coliform and nitrate. DEP does not certify radon-in-water laboratories. The Radon Division keeps a list of people who offer that test and will send it on request. Call the published hotline 800-237-2366 (or 717-783-3594) and ask for the radon-in-water list. Do not treat a coliform certificate, or a name on the indoor-air Radon Services Directory, as a radon-in-water credential.

Penn State Extension’s testing page says radon is a specialized collection: a lab employee usually has to visit the house. Call the lab on that DEP list about the bottle, the hold time, and whether they collect. Ask for untreated kitchen cold unless they tell you otherwise.

CDC’s well-testing guidance is the federal annual floor: total coliform, nitrates, total dissolved solids, and pH, using a state-certified lab. Radon-in-water is an extra you request when the geology or a neighbor’s sheet puts it on the list — not a substitute for that annual pair.

A store kit is a screen. It does not replace a certified radon-in-water method. Well water test kits explains that split. If you want a mail-in panel while you wait on a Pennsylvania lab, Tap Score / SimpleLab is an approved class example of a mail-in certified-lab kit — not a ranked pick. Bacteria or nitrate on the same sheet still goes to the health department. SpringWell is an official catalog URL, labeled application pending. SpringWell is not a radon-treatment brand on this page. See the disclosure.

Bacteria or nitrate on the same sheet still goes to the health department, even on a radon page. Circle those lines first. Then read how to read a lab report.

Indoor-air 4 pCi/L is not a water number

EPA’s radon pages use 4 pCi/L as the indoor-air action guideline. DEP’s Radon Division is the state indoor-air program. The published Radon Division hotline is 800-237-2366 (office phone 717-783-3594). Call that number for indoor-air testing and mitigation questions. Do not use it as a substitute for a drinking-water lab.

A water result is picocuries per liter of water. An air result is picocuries per liter of air. Same unit name. Different samples. Different programs. If a salesperson compares your kitchen sheet to 4, they are mixing tests. Ask which matrix the number came from before you compare anything.

EPA proposed 300 and 4,000 pCi/L are comparison only

On November 2, 1999, EPA published a proposed National Primary Drinking Water Regulation for radon-222. The proposal named a maximum contaminant level of 300 pCi/L, an alternative maximum contaminant level of 4,000 pCi/L, and a maximum contaminant level goal of zero. Those numbers were written for community water systems if the rule had been finalized. Best available treatment in the proposal was aeration or granular activated carbon.

The rule was never finalized. It is not a Safe Drinking Water Act limit on a private well. DEP does not adopt it as a kitchen-tap statute. Use 300 and 4,000 only as published comparison lines so you can read a USGS map or a lab footnote that cites them. Penn State Extension’s water-report page also lists 300 pCi/L next to radon as a comparison number — the same proposed-MCL line, not a private-well legal limit.

Units still trip people. If the sheet prints pCi/L, that is the comparison unit on this page. If the reporting limit sits at or above 300 pCi/L, you bought a test that cannot tell you whether you are under the proposed MCL line. Ask for a lower reporting limit. This site will not turn the line into a risk score.

USGS SIR 2017–5018 is not your well

USGS Scientific Investigations Report 2017–5018 (Gross), prepared with the Pennsylvania Department of Health and DEP, evaluated 1,041 groundwater samples collected from 1986 through 2015 in 16 geologic units that each had at least 25 radon results. About 87 percent of those samples were at or above the proposed MCL of 300 pCi/L. About 14 percent were at or above the proposed AMCL of 4,000 pCi/L. The highest groundwater concentrations were in Piedmont schists, gneisses, and quartzites. The Peters Creek Schist (Xpc) was the unit whose median exceeded 4,000 pCi/L.

That is a research set of groundwater samples aggregated by geologic unit — mixed well types, not a census of every Pennsylvania kitchen tap, and not a county ranking. USGS states that the associated data and maps are not recommended for predicting individual concentrations at specific sites and are not a decision-making tool for a property owner deciding whether to test a given location. Repeat that when someone opens a geologic map and tells you the township is “high” or “fine.” Your well is a hole in a specific unit. The only number that counts is the certified-lab result from that hole.

DEP does not regulate the kitchen tap

DEP’s private-well water-testing page states that private wells are not regulated the way public systems are. Owners are responsible for testing. For coliform, nitrate, and other drinking-water fields, use a laboratory on DEP’s accreditation search. For radon-in-water, DEP does not certify the lab — it lists providers. This site’s certified-labs index and the Pennsylvania inventory only tell you how to use the drinking-water search and where the radon hotline sits.

The Radon Division is still the indoor-air contact: 800-237-2366. A high indoor-air test and a high water test are two different follow-ups. This site does not collect samples, does not mail kits, and does not read a sheet for you. Do not send a lab report to Well Diagnosis.

Treatment class only after a sheet

Do not shop a tank because a USGS unit is orange, or because a neighbor’s basement air test was high. After you have a water number, the treatment classes named for radon-in-water are aeration and granular activated carbon / charcoal, installed as point-of-entry after the pressure tank. Point-of-use at one kitchen tap does not address radon that leaves the water at showers, washers, and other whole-house uses.

Those are classes, not a shopping list. Look a model up in the NSF drinking-water treatment unit database. NSF is a claim on a listed model, not a badge this site awards. Do not rank brands. Do not treat SpringWell as a radon specification; it is an official catalog URL labeled application pending.

If bacteria is present, stop. Health department first. A carbon bed or an aerator on a contaminated well is the wrong Monday. A radon class still has to sit in a sane treatment order after the pressure tank. Iron, hardness, sediment, and hydrogen sulfide on the same sheet change what can live upstream of aeration or carbon. A fouled unit is how a class fails.

Bottom line

Radon in Pennsylvania well water is invisible in the glass and easy to confuse with indoor air. Order a certified-lab radon-in-water test from the Pennsylvania inventory. Keep EPA’s indoor-air 4 pCi/L on the air side. Use the proposed 300 and 4,000 pCi/L water lines as comparison only — they are not private-well legal limits. USGS SIR 2017–5018 describes geologic units, not your well. DEP does not regulate private wells. For indoor-air radon, DEP’s Radon Division is 800-237-2366. Treatment class — aeration or GAC, point-of-entry — comes after the sheet. Bacteria and nitrate still go to the health department. See the disclosure for affiliate status.