When we think about radon gas sneaking into our homes, we usually picture it seeping up through cracks in the basement floor or gaps in the foundation. But there’s another, often-overlooked pathway that this invisible, odorless gas can take: your water supply.
If you get your water from a private well, everyday activities like taking a hot shower, running the dishwasher, or even washing your hands could be releasing radon gas directly into the air you breathe. Here is a breakdown of how this happens, the correlation between radon in your water and air, and how to find out if your plumbing is the culprit.
How Does Radon Get From the Sink to the Air?
Radon is a naturally occurring radioactive gas produced by the breakdown of uranium in soil and rock. When groundwater flows through these rocks, radon gas can dissolve into the water. If your home relies on a private well, that water gets pumped straight into your plumbing system, carrying the trapped radon with it.
The radon stays trapped in the water while it’s enclosed in your pipes. But the moment that water is released and agitated, the gas escapes into the surrounding air.
Think of it like opening a shaken bottle of soda. The carbon dioxide is trapped while the cap is on, but once you open it and pour, the bubbles aggressively escape. The same thing happens with radon-rich water when it goes through:
- The Shower: The spraying action of the showerhead, combined with the heat of the water, makes it incredibly easy for radon to off-gas into the small, enclosed space of a bathroom.
- The Washing Machine & Dishwasher: The aggressive sloshing and high temperatures release trapped gas into the laundry room or kitchen.
- The Kitchen Sink: Running the faucet to wash dishes or hands aerates the water, allowing radon to slip out.
The 10,000-to-1 Rule: Correlating Water to Air
You might be wondering: If there is radon in my water, how much is actually ending up in the air?
Scientists and the Environmental Protection Agency (EPA) use a general rule of thumb to estimate this correlation: the 10,000-to-1 rule.
For every 10,000 picoCuries per liter (pCi/L) of radon in your water, it will contribute approximately 1 pCi/L of radon to your indoor air.
- Example: If your well water tests at 30,000 pCi/L for radon, everyday water usage will add roughly 3 pCi/L of radon to the air in your home.
While that might seem like a small addition, the EPA strongly recommends fixing your home if your indoor air radon levels are at or above 4 pCi/L. If your home is already pulling 2 pCi/L from the soil, that extra 3 pCi/L from the water pushes you over the danger line.
How to Know if Water is the Source of Your Radon
Figuring out exactly where the radon is coming from is a step-by-step process. Here is how you can determine if your water supply is the primary suspect:
1. Check Your Water Source
If your home is connected to a public municipal water supply, you generally don’t need to worry about waterborne radon. City water is treated, aerated, and usually travels through miles of pipes before reaching you, allowing the radon to safely vent off into the atmosphere long before it hits your tap. If you have a private well, water is a potential source.
2. Test the Air First
Always start by testing the air in your home, as inhalation is the primary health risk associated with radon. You can purchase a DIY short-term test kit from a hardware store. If the air test comes back elevated (close to or above 4 pCi/L), move on to step three.
3. Test the Water
If your air levels are high and you are on a well, it’s time to test the water. Do not use an air testing kit for your water. You need a specific radon-in-water test kit. This usually involves carefully collecting a water sample from a faucet (without aerating it) and sending it to a certified laboratory.
4. Do the Math
Once you have both results, apply the 10,000-to-1 rule. If your air levels are 6 pCi/L, but your water only has 5,000 pCi/L of radon (contributing 0.5 pCi/L to the air), your primary problem is the soil beneath your foundation, not the water. However, if your water tests at 40,000 pCi/L, it is a significant contributor to your indoor air problem and needs to be addressed.
Protecting Your Home
If you discover that your well water is high in radon, don’t panic. There are highly effective mitigation systems available, such as Aeration Systems (which strip the gas from the water before it enters your plumbing) and Granular Activated Carbon (GAC) filters.
Knowledge is the best defense. By testing both your air and your well water, you can ensure that your relaxing hot shower isn’t secretly compromising your indoor air quality.