This is part two of the post "Reducing Radon Levels in Michigan Well Water". This article goes into standards, traditional systems and costs. Hope you find this post helpful.
Reducing Radon Levels in Michigan Well Water
A few days ago, I wrote about radon in Michigan drinking water... specifically, well water. As promised, here is the information on reducing radon -- if you have a dangerous amount in your tested sample.
U.S. Standards and Michigan Standards
The Environmental Protection Agency (EPA) has a danger level for radon levels in a house: 4.0 pCi/L. (If this pCi/L scale doesn't make sense, please read this brief explanation to get up-to-speed.)
Unfortunately, the EPA has not issued a similar danger level for public water supplies (although standards are in the works) -- and private water supplies (like wells) are out of the EPA's jurisdiction.
However, nine states currently have guidelines for radon in drinking water: New Jersey, Pennsylvania, New Hampshire, Maine, Rhode Island, Connecticut, Vermont, Massachusetts and Wisconsin.
Of course, Michigan is not in that list, so that means... there is no "official" standard here. So here are a few suggestions about levels of radon in water that I'd recommend be considered the "action level."
First off, the rule of thumb is that 10,000 pCi/L in the water contributes 1 pCi/L to radon in a house. The Michigan Department of Environmental Quality (MDEQ) recommends that you first test your indoor air quality. If you have a level above 4.0 pCi/L, focus on lowering the radon levels through traditional mitigation. If your levels are still high, then move on to working on the water supply.
Or, in their words,
MDEQ recommends that elevated indoor radon levels be treated first as a soil gas problem, using conventional radon reduction techniques in an attempt to lower those levels. Radon in water testing need not be routinely conducted, and would be recommended only if the conventional techniques are not successful. Then the homeowner may wish to test the water to determine whether it is contributing to the radon in air levels.
Next, there is a great variety of action levels suggested between the nine states listed above. Maine has an action level of 10,000 pCi/L. New Jersey is suggesting 800 pCi/L. The proposed EPA action level for public water sources is 300 pCi/L.
So, with the lack of an "official" Michigan action level number, I'd throw out 10,000 pCi/L or above as a minimum action level... if you already have levels of radon gas approaching or above 4.0 pCi/L.
Reducing Radon Levels
Basically, there are two traditional systems to reduce the levels of radon gas in wells: aeration and granular activated carbon (GAC).
The Granular Activated Carbon (GAC) system generally removes 85% of the radon in the water. It is cheaper than an aeration system, generally around $1,500 to $2,000 to install.
The GAC tank is installed after other water treatment systems (like a water softener), and is filled with activated carbon which traps radon. Fresh carbon holds about 85% of radon atoms until they decay.
GAC systems work well for moderate levels of radon in well water. For higher levels, consider an aeration system.
The aeration system works like this: water comes in from the well, is treated, and goes to the faucet. Radon gas goes out a tube at the top of the tank and exits from the house just like in a traditional radon mitigation system.
This kind of system reduces about 95% of the radon in the water, and is generally more efficient than the alternative method, GAC. Unfortunately, it costs much more, generally starting at about $3,000 and moving upwards toward $5,000.
You can learn more at michigan-indoor-air-quality.com/radon.html
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