How often should you check a radon mitigation fan?
Updated July 2026
Glance at the U-tube manometer on your radon system's pipe every month to confirm the fan is still pulling suction. The two liquid columns in that little gauge should sit at different heights; when they level out, the fan has quit or the pipe is blocked. The fan itself runs 24/7 and lasts about 5 to 10 years before it wears out. Because a dead fan sets off no alarm, radon quietly climbs back toward its pre-system level until a test or a manometer check catches it.
What changes the interval
| Your situation | Interval | Why |
|---|---|---|
| Monthly manometer glance | Every month | Offset liquid columns mean the fan is working; level columns mean failure |
| Fan replacement | Every 5–10 years | The inline fan runs continuously and eventually wears out; $150–400 for the part |
| Columns suddenly level or equal | Investigate now | That points to a failed fan or a blocked or frozen vent pipe |
| After the fan is replaced or serviced | Retest radon | Confirm the new fan is actually pulling levels back down |
| Radon retest with the system running | Every 2 years | The gauge shows suction, not the radon number, so you still test |
| No manometer, or a broken one | Add or replace it | A $10–20 gauge is the only cheap indicator that the fan has failed |
| Fan noise, rattle, or silence | Inspect the fan | A failing bearing usually warns with noise before it stops entirely |
The cost of skipping it
What skipping it costs: most mitigation systems have no alarm, so when the fan dies nothing beeps and radon creeps back up over days to weeks. Since radon is the second-leading cause of lung cancer in the US, a fan that failed months ago and went unnoticed quietly erases the protection you paid roughly $800–2,500 to install. A replacement fan is $150–400 plus install, and pairing the monthly manometer glance with a radon retest every 2 years is what keeps the system honest. The check itself is free.
How to do it (1 minute monthly · DIY)
- Find the vertical PVC pipe (in the basement, garage, or run up the outside wall) with a small clear U-shaped gauge attached.
- Confirm the two liquid columns sit at different heights; that offset is the suction the fan is creating.
- If the columns are level, the fan has failed or the pipe is clogged or iced, and the system needs service.
- Listen for the fan's steady hum, usually up in the attic, garage, or outside; sudden silence or a rattle is a warning.
- Note the fan's install date and plan to replace it at 5 to 10 years, before it fails outright.
- After any fan replacement, retest radon to confirm the level is back below the 4.0 pCi/L action mark.
Knowing the interval is the easy half. OnOtto reminds you at the right interval, and it won't let you snooze it into next year. Tasks persist until they're done, and completing radon fan checks schedules the next one automatically.
Put this on autopilot, free for 30 daysFrequently asked questions
What does the manometer on my radon pipe tell me?
It shows whether the fan is pulling suction on the pipe. The two columns of liquid should sit offset, at different heights, which means air is being drawn out from under the slab. If the columns level out and read equal, there is no suction, meaning the fan has stopped or the pipe is blocked. What the manometer does not show is the actual radon level, so a working gauge is not a substitute for a radon test every 2 years.
How long does a radon fan last?
A radon mitigation fan typically runs 5 to 10 years of continuous 24/7 operation before it wears out. You will often get a warning first: a louder hum, a rattle, or vibration as the bearings age. Replacement runs about $150–400 for the fan itself plus installation labor, and it is important to match the new fan to the pipe size and the suction the system was designed around. Undersizing it can leave the slab under-vented even though the fan is spinning.
My radon fan is quiet, is it broken?
Not necessarily. Radon fans are designed to run continuously and fairly quietly, so a soft hum is normal and healthy. What tells you it stopped is the manometer: if the columns have leveled out and gone equal, there is no suction and the fan is likely dead, even if you cannot hear a change. Before assuming a failure, confirm the fan still has power at its switch or outlet, since a tripped breaker or bumped switch can silence it just as convincingly.
Does a mitigation system mean I never have to test for radon again?
No. The system lowers radon, but it can fail silently, so testing is still how you confirm it is doing its job. Retest every 2 years, and again after any fan replacement or major work on the house. Think of it as two separate checks: the monthly manometer glance confirms the fan is pulling suction, and the periodic test confirms the radon level itself is actually low. Neither one replaces the other, and skipping the test is how a dead fan hides.