The system nobody handed you a manual for
This guide is for two kinds of people. Owners who had a radon system installed years ago and haven’t thought about it since. And buyers who just closed on a house that came with a white pipe, a little gauge, and no explanation.
Both are in the same boat, and it’s a decent boat: a radon system is one of the simplest machines attached to a house. One fan, one pipe, one gauge. No filters to change, no seasonal startup. It either pulls or it doesn’t — and it will tell you which, if you know where to look.
The checks below take five minutes and no tools. They won’t make you a technician, and they’re not meant to diagnose your particular system from a webpage. A check that looks wrong means get it looked at, not start ordering parts. What they will do is teach you what your system is saying, so a dead fan gets noticed in a week instead of at the next home sale. (If you want to know what each part actually does first, how radon mitigation works is the ten-minute tour. If the fan’s already dead, skip straight to fan replacement.)
The five-minute check
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Look at the gauge
Uneven fluid in the u-tube means suction. Level fluid means the system isn't pulling.
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Listen for the fan
A soft, steady hum near the fan is normal. Silence or new rattling isn't.
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Follow the pipe
Scan the run for cracks, sagging joints, or a discharge blocked by ice or debris.
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Check the power
A tripped breaker or an unplugged fan switch is a surprisingly common culprit.
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Mark the fluid line
A pen line at today's level makes any future change obvious at a glance.
The gauge is the whole dashboard
The u-tube manometer, that little clear tube of colored liquid on the pipe, measures one thing: whether the pipe has suction.
A running fan holds a slight vacuum in the pipe. That vacuum pulls the fluid up on one side and down on the other. So uneven fluid is the good reading. It means the fan is pulling and the system is doing its job.
Level fluid is the finding. No vacuum, no suction. Maybe the fan died, maybe a breaker tripped, maybe someone unplugged it to run a shop vac in 2023. The gauge can’t say which. It only says the system has stopped, and the house is drifting back toward its pre-mitigation number.
Worth knowing about the hardware doing the work: radon fans run continuously, every hour of every season, and in industry experience they commonly last on the order of a decade. Not a defect, just duty cycle. A system installed when your kid started middle school is due for skepticism by the time they finish college. When the gauge goes level and the power checks out, the fan is the usual suspect, and replacing it is routine, quick work compared to the original install.
One habit beats everything else on this page: take a pen and mark today’s fluid level on the gauge housing. Suction varies slightly house to house, so your normal is the baseline that matters. With a mark, any future glance answers the question in one second.
Gauge says something's off? Have it looked at
When to make the call
Four signs say a service visit is warranted, none of them subtle:
A silent fan. If you used to hear the hum outside the basement wall or up in the attic and now you don’t, believe your ears over your optimism.
A new noise. Grinding, rattling, or a hum that’s grown louder usually means bearings on their way out, or vibration working a mount loose. Fans rarely heal.
Level gauge fluid after you’ve checked the breaker and the plug. Covered above; that’s the system flatly reporting no suction.
Visible damage. A cracked pipe, a joint weeping condensation, a discharge capped with ice after a hard cold snap, or daylight where the roof flashing should seal.
And one thing that isn’t a warning sign but belongs here anyway: even a system that passes every check deserves a retest every couple of years. The gauge proves suction, not radon levels. A partially blocked suction pit can hold vacuum while the basement creeps up. A periodic test is the only reading that measures the thing you actually care about. Between the five-minute check and a retest on the calendar, a system kept in repair will quietly do its one job for decades.