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Radon in water general information

Colorado's pREMIER rADON In WATER Testing LAB. 

Radon, a radioactive gas that is continuously made in the soil and rock beneath our homes from the radioactive breakdown of uranium and radium, moves through the soil and can enter the house, the atmosphere or even the water table that is used by your well.


Generally speaking, if your water is supplied by a well, either your own private well or a public drinking water system that uses a well, there is a chance that you will have some radon in your water unless it has been treated. Water taken from streams, reservoirs, cisterns, or any water supply open to the atmosphere, is not expected to have measureable radon because the radon has already escaped to the atmosphere prior to being pumped into the house or the distribution system. If you find that your radon is elevated, once you get back your radon in water result, and you are on a public drinking water system, you should contact your water provider for further information or advice. If your own private well has radon above your comfort level, you will be responsible for any radon reduction. The two common treatment systems are discussed in the second page and following, of this hand-out, a document provided by the U.S. EPA. You can click on the URL of that document and download it, if you wish. The EPA does not copyright its documents.


Why is radon in water a concern?


Once your water is brought into the house, radon can escape out of the water and enter the house air and be breathed in. This is the main concern. The radon, of course, can also be consumed when you drink your water. However, a nation-wide study done by the National Academy of Science in the late 90’s, calculated that fewer than 170 cancers a year nationally were caused by radon in water, about 17 of these being stomach cancer from ingestion, the rest being lung cancer from the radon that degassed into the air and was breathed in by the occupant.


Are there regulations on the levels of radon in water?


No. The U.S. EPA attempted to set a minimum contaminant level (MCL) of 300 pCi/L for community water systems (4000 pCi/L if the water provider’s state instituted an education program). That MCL was never promulgated. No attempt was ever made to control the level of radon in private wells. So, as things stand now, the radon in your private well water is not regulated at all.


Why should I test my well?


There is a rule of thumb that has been used for many years that for each 10,000 pCi/L of radon in the water, an additional 1 pCi/L of radon will be released into the indoor air by daily use of the water while showering, washing dishes, etc. So, if earlier testing of your indoor air has shown an elevated level (say, 4.0 pCi/L or higher, then, testing your water may reveal that a significant portion of the indoor radon is degassing from your water and you may decide to mitigate the water. For example, if your air contains 4.0 pCi/L and your water contains 30,000 pCi/L of radon, then, using the 10,000 to 1 rule of thumb, of the 4 pCi/L in your indoor radon, most (3 pCi/L) is coming from radon degassing from the water and you may consider treating the water. (3 is 1/10,000 0f 30,000)


It is always recommended, for this reason, to test your home air for radon, prior to, or along with a radon in water test, in order to judge if water treatment is worthy of consideration.  


How does Radon Measurements Lab calculate the radon in your well water?


You, the homeowner are an important part of this process. When you purchase a test kit, you will receive a detailed instruction sheet. Care is required on your part while sampling your water. Read the instruction sheet thoroughly and do not start the sampling until you understand all of it. It is especially important that the water you sample has run long enough so that you are not sampling water from your pressure tank or holding tank. Next, it is important that both bottles are filled one right after the other and that neither has any air bubbles in it when it is capped. Finally, the back of the instruction sheet has a report form on it. You must fill out all of the report form in order for us to calculate the radon in the water.


When we receive your samples, we will measure the alpha particle activity in the radon-222 and two of its decay products, polonium-218 and polonium-214, which occur naturally in the water. We will compare that activity to three standards made by the U.S. EPA and already programmed into our computer. The alpha particle counter uses liquid scintillation as recommended by the standard 7500 RN. The counter is made by Hidex, the model is a Triathler. It is a state of the art liquid scintillation counter. We also follow the recommendations made by the American Association of Radon Scientists and Technologist (AARST) radon in water advisory committee (MW-RN) currently in draft form, and will continue to follow this committees decisions once they are formally adopted by AARST.


We will measure and report both vials and give you a radon value for both and a relative percent difference (RPD) between the two numbers. Generally speaking, a radon value of 100 pCi/L is the lowest that can be reliably measured and is called the MDL or minimum detectable level (which is equivalent to adding 0.01 pCi/L to your indoor air). For high radon, above 4000 pCi/L, a 10 % RPD is expected, but this low of an RPD requires that you followed the instructions carefully and returned the samples promptly, preferably UPS or FedEx overnight.


Can the radon in water be reduced?


Yes, for radon below 4000 pCi/L to 5000 pCi/L, a simple granulated activated charcoal (GAC) filter will often reduce the radon to below 100 pCi/L. This filter is installed professionally in the main water line, and not at one of the water faucets. This is not one of the water filters that is purchased at a hardware store for a single tap (point of use). Check online for purchase or rent.


Radon above 5000 pCi/L is normally mitigated using an aeration system. Here, the water coming into the house is sprayed in a sealed tank which resembles an old-fashioned clothes washer, and fresh air is also brought in to strip the radon out of the water. That air is then exhausted safely above the eave line, similar to a radon in air mitigation system. The cleaned water is then again pumped up to pressure and put back into the water line for distribution throughout the house.

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