You Have a Radon System. Now Read the Gauge
Plenty of folks pay a few thousand dollars for a radon mitigation system, watch it get installed, and then never look at it again. The problem is that a mitigation system is basically a fan and a pipe, and fans don't run forever. When the fan quietly dies, the radon comes right back, and nothing in the house tells you except one small part most people walk past every day: the manometer.
The U-tube on the pipe is doing a job
Look at the vertical white PVC pipe running from your basement or slab up through the house. Somewhere on it, usually at eye level, there's a small clear tube shaped like a U with colored liquid in it. That's the manometer, and it's the single most useful thing on the whole system.
When the fan is running and pulling suction on the soil under your house, it pulls one side of the liquid higher than the other. So the two columns of liquid should be uneven, offset from each other. That offset is proof the fan is moving air. If the two sides ever sit at the same level, dead even, the fan has stopped pulling suction, and your system is not protecting you anymore.
How long a radon fan actually lasts
Radon fans run 24 hours a day, 365 days a year, from the moment they're installed. Most manufacturers rate them for somewhere in the range of five years or so, and while plenty last longer, a fan that's been humming along for a decade is living on borrowed time. When it goes, it usually just gets quiet, no alarm, no smell, nothing. The manometer going level is often the only clue.
Get in the habit of glancing at that U-tube once a month, and put your hand near the fan (it's usually outside or in the attic) to feel for the low vibration and hum. A fan swap is a fraction of the cost of the original install, and it's not something to put off, because a dead fan means you've been breathing whatever your soil is putting out with no protection at all.
| What you see | What it means | Do |
|---|---|---|
| Liquid uneven (offset) | Fan is pulling suction, working | Nothing, that's good |
| Liquid dead even | Fan stopped, no protection | Call for a fan replacement now |
| Fan silent / no vibration | Motor likely failed | Replace the fan, then retest |
| System 8+ years old | Fan near end of life | Plan for a swap, retest air |
Why you retest even when the gauge looks fine
A working manometer proves the fan is moving air. It does not prove your indoor radon is below the action level. Sealing can shift, soil conditions change, an addition changes the airflow. The EPA's guidance is to retest your home's radon every two years even with a working system, and any time you do major work on the house. Radon is measured in picocuries per liter (pCi/L), and the EPA's action level is 4.0 pCi/L. A short-term test kit costs less than a tank of gas.
Joe, the septic-ignoring, well-neglecting legend himself, finally got a radon system after his number came back at 9. Install day he watched the manometer show a nice offset and figured that was that. Six years later the fan seized in the dead of winter, the liquid went dead level, and Joe never looked. He found out only because he finally bought a $15 test kit on a whim and it read 8.6, right back where he started. Two years of protection he thought he had, gone, because he never glanced at the one gauge that would've told him. Read the tube, Joe.
The one-minute monthly habit
Glance at the manometer, confirm the liquid's uneven, and confirm the fan is humming. Once every couple of years, run a fresh test kit. That's the entire maintenance routine, and it's the difference between a system that protects you and an expensive pipe that just looks reassuring.
The EPA lays out the health basis for the 4.0 pCi/L action level and its testing guidance here: Health Risk of Radon (EPA). Radon is the second-leading cause of lung cancer in the U.S., so a dead fan you never noticed is not a small thing.