The contaminant that changes rooms
Radon in water treatment for Maine wells
Radon rides into a Maine house dissolved in well water, then leaves the water the moment it meets air: shower spray, a running dishwasher, a filling washing machine. What started as a water number becomes an indoor air number. Maine's guideline for radon in private well water is 4,000 pCi/L, set out in the state's Maximum Exposure Guideline FAQ.
Bedrock wells in granite country carry the risk, and Maine has a lot of both. This page covers how big the problem is here, how waterborne radon reaches your lungs, and what aeration and carbon systems honestly cost.
How radon moves from the tap to the lungs
Radon is a radioactive gas dissolved in the water while it is under pressure underground. Run a tap, and it off-gasses into the room, most efficiently wherever water is heated or sprayed. EPA's long-standing rule of thumb: 10,000 pCi/L of radon in the water supply contributes roughly 1 pCi/L to indoor air in a home with average air exchange, per EPA's radon in drinking water pages. EPA identifies radon exposure as a leading cause of lung cancer among nonsmokers, and its indoor air action level is 4 pCi/L, per the agency's action level guidance.
That ratio explains the strategy. A well at 20,000 pCi/L is quietly adding about 2 pCi/L to the household air on its own, half the air action level, before any soil-gas radon is counted. Water treatment removes that contribution at the source. It does not touch radon seeping up through the foundation, which is a separate, air-side fix. The way to know which problem you have, or whether you have both, is to test both: water through a certified lab (the testing page covers kits and costs) and indoor air with a standard radon test.
The two treatment paths
Aeration: the workhorse
An aeration system bubbles or sprays air through the incoming water in a tank, strips the radon out, and vents it above the roofline before the water continues to your taps. EPA lists aeration as the best available technology for radon in drinking water, per its radon in water guidance. It handles the full range of concentrations Maine bedrock produces, and it needs power, floor space, a repressurization pump, and a vent run.
Cited costs: $6,000 to $8,000 installed in the Maine and New Hampshire market, per a regional installer's published pricing; national figures run $4,000 to $5,000, per HomeGuide.
Granular activated carbon: the narrow case
A GAC tank adsorbs radon onto carbon media as water passes through. It costs less than aeration and has no vent or blower, which makes it attractive at lower concentrations. The caveat is physics: radon decays on the media, so at higher water concentrations radioactivity accumulates in the tank over time, which raises where-to-put-it questions and can complicate disposal of spent media, a limitation EPA notes in the same guidance.
The practical result: professionals in Maine tend to reserve GAC for modest exceedances and specify aeration as the number climbs. The lab result makes the call, not the price list.
What sizing and installation actually involve
An aeration quote is built from three inputs: the lab concentration, which sets how much stripping the system must do; the household's peak water demand, which sets tank and pump capacity; and the house itself, which decides where the tank sits and where the vent can run. The vent matters more than owners expect, since the radon stripped from the water has to discharge above the roofline, away from windows, the same discipline air-side mitigation follows. Basements with a reasonable vent path make for clean installs; tight crawlspaces and finished lower levels take more creativity and sometimes more money.
After startup, the system needs what most well equipment needs: an occasional look at the blower and repressurization pump, and a retest of the treated water to confirm the reduction, then again on the normal three-to-five-year cadence from the Maine testing schedule. GAC systems swap the blower maintenance for media changes on a schedule a professional sets from your concentration.
The air test connection
Radon is the one Maine water problem that is really two problems wearing one name. A house can have high radon in water, high radon in air from soil gas, or both, and the fixes do not overlap: a water aeration system does nothing for soil gas, and a sub-slab air mitigation system does nothing for the water. Maine CDC's radon guideline FAQ frames the 4,000 pCi/L water number in exactly this air context, and it comes up constantly in real estate, where both tests are commonly ordered together. Buying or selling, the sequence is laid out in the home purchase guide.
After a water system goes in, retest both sides: the treated water to confirm the reduction, and the indoor air to see where the whole house landed. Since radon shares its bedrock origins with arsenic and uranium, wells over the radon guideline often have company on the report; the whole-house page covers stacked problems, and the results explainer reads the full panel line by line.
Get an aeration quote built from your number
Radon work in Maine is specialized: venting, placement, repressurization, and sizing all follow the lab result and the house. Tell us your town and your water number, and we connect you free with an independent local professional who installs radon water systems. If you only suspect radon so far, the match starts with a certified test instead.
The referral fee comes from the professional and never raises your price; the arrangement is spelled out on the how we make money page.
Questions Maine well owners ask
- What is Maine's guideline for radon in well water?
- Maine's guideline, called a Maximum Exposure Guideline, is 4,000 pCi/L for radon in private well water. It is a health-based guideline rather than an enforceable limit, since private wells are unregulated. In practice it is the number Maine labs, real estate transactions, and treatment professionals all work from.
- Is a result over 4,000 pCi/L an emergency?
- No, and nobody credible will treat it like one. Radon risk is about long-term exposure, so the sensible pace is deliberate: confirm the number, test the indoor air as well, and get treatment quoted. A result several times the guideline argues for moving in weeks rather than years, but the fix is routine equipment.
- Aeration or carbon: how is that choice made?
- Mostly by the water number. Aeration handles the full range Maine wells produce and is EPA's listed best available technology, at a higher install price. Carbon systems cost less and can fit lower concentrations, but at higher levels radioactivity builds up on the media, raising placement and disposal issues. A professional sizes from the lab report.
- Will treating my water fix an indoor air radon problem?
- Only the share that came from the water. EPA's rule of thumb is that 10,000 pCi/L in water adds about 1 pCi/L to indoor air, so most airborne radon usually enters from soil under the foundation instead. That is why the air test and the water test travel together: each points at its own fix.
- What does radon water treatment cost in Maine?
- Cited figures put aeration systems at $6,000 to $8,000 installed in the northern New England market, against a national range of roughly $4,000 to $5,000. Carbon-based systems run less up front but carry media replacement, and past a point the water number rules them out. Quotes should be built from your lab result.