Radon in well water can contribute to the indoor air levels of radon in your home. Radon is released into the air as the water pours into sinks, tubs and appliances. Household activities that use hot water, such as showering and washing dishes or clothes, can release large amounts of radon particularly in the rooms where this water is used. Scientists are now looking at the possibility that the drinking of water with high amounts of radon may cause other types of cancers.

The concentration of radon in water is usually given in picocuries per liter (pCi/L) as in air measurement of radon. While the average concentration of radon in U.S. groundwater is below 1,000 pCi/L, some levels of groundwater have been found above 1,000,000 pCi/L. The highest amounts have been found in the Northeast. Private wells tested in Connecticut indicate an average radon level of about 3,000 pCi/L. There are reduction systems available which are very effective in reducing any elevated level of radon in water.

Radon Testing
The State of Connecticut Department of Health Services Radon Program recommends that you test your water for radon if your water comes from a private well. Be sure to use a laboratory that follows an EPA approved testing method. Since radon levels may change over time, it is useful to obtain a second test (if time permits) during another season. The results can be averaged together to assess your risk from radon in water.

Understanding Your Water Test Results
The U.S. Environmental Protection Agency (EPA) has proposed a standard of 300 pCi/L of radon in public drinking water. As discussed earlier, the average radon concentration in private wells in Connecticut is 3,000 pCi/L or ten times the proposed standard. Therefore, it is likely that your private well water has radon levels in excess of the proposed public water standard. While public drinking water supplies are the responsibility of the utility companies, a private well is the responsibility of the homeowner. The following section will help you decide if you need to take action to lower the radon level in your water.

Making a Decision About Radon in Water
Since water radon treatment systems are expensive (ranging from $800 to $4,000), the decision to treat your water should be made carefully. The following questions should be answered to help you decide if your water should be treated for radon.

1. Will the radon released into the air from your everday water use equal or exceed the current EPI indoor air guideline of 4 pCi/L or is your radon in water level 40,000 pCi/L or higher?

To answer these questions, you must first know the amount of radon that is transferred from the household water to the household air. Of primary concern is the radon in household air, since breathing this radon will place you at risk for lung cancer. You can find out the amount of radon released into the air from the water by using the following rule:

Every 10,000 pCi/L of radon in water contributes about 1 pCi/L of radon to the radon level that already exists in the household air. (This estimate can vary, depending on your water use.) Therefore, if your radon in water level is 40,000 pCi/L or higher, you should treat the water since the radon from the water alone will equal or exceed the 4 pCi/L guideline.

2. Is your radon in water level between 5,000 and 40,000 pCi/L?

At these levels there is still a significant risk of lung cancer from breathing radon and a lesser risk of stomach cancer from ingesting it. Your water should be treated. However, if the amount of money that you have budgeted for radon reduction is limited, it is more important that you ensure that air levels are below 4 pCi/L by controlling soil gas entry routes.

3. Is your radon level between 1,000 and 5,000 pCi/L?

There is a risk for development of lung cancer from exposure to radon at any level. However, the indoor air concentrations resulting from these radon in water levels may be similar to your outdoor or background levels. Therefore, treating water at this level may not be worth the expense.

4. Is your radon in water level between 300 and 1,000 pCi/L?

Reduction of radon below these levels may not always be possible or practical in private wells. Evidence at this time suggests that radon in water at these levels represents the lowest range of health risk and further action is not recommended because of current costs of reducing radon in water.

Reducing Radon In Water
Removing radon from the well water before it enters the house is the most effective treatment. Radon levels in the water can be reduced either by the use of a granulated activated carbon (GAC) filter unit or by the use of an aeration treatment system. The type of reduction method depends upon the radon level and how much water is used.

The GAC system has special charcoal filters which remove the radon from the water. Typical GAC systems cost between $800 and $1,500. GAC units will build up radioactive decay particles with use. The amounts of radiation accumulated by a GAC depends on the amount of radon in the well water and the amount of well water used. Your GAC filter should be changed periodically according to the recommendations of the manufacturer. Not doing so will result in the filter itself becoming an additional source of radiation requiring special disposal, and could result in bacterial contamination as well. Use of GACs for treatment of radon is normally limited to wells with radon levels from 5,000 to 10,000 pCi/L.

The aeration system forces the radon gas from the water by using air bubbles or other methods and vents it outside the home. Typical aeration systems cost between $2,500 and $4,000. The removal of radon from the water by the aeration unit may result in very high levels of radon in the air. Therefore, it is extremely important that the aeration unit's radon-laden air be vented away from the home, where it will not leak back into the house. The vent pipe for the aeration unit should be placed above the roofline.

Wells with very high levels of radon may also contain high levels of radium and uranium. Separate tests are required to identify these elements. An additional activated charcoal or resin bed filter may be needed to treat these contaminants. The filters should be maintained according to the manufacturers recommendations.

There are maintenance and installation concerns with either type of radon treatment unit. Be certain that all appropriate permits are obtained and state and local building code requirements are met during installation of these units.