Radon Fan Stopped or the Manometer Reads Zero: What to Do
September 1, 2026
A manometer showing two equal liquid levels means the system is not pulling suction. Usually the fan has failed, sometimes the pipe is blocked or a breaker tripped. The house is back to its pre-mitigation radon level until it is fixed.
Reading the gauge
The U-tube manometer on the vent pipe is the only status indicator most radon systems have. At install, the fan pulls one column of liquid down and the other up, and the installer marks the offset on the label. That offset is the normal reading for that system.
Two equal levels mean zero suction. A reading well below the install mark means reduced suction, which points to a tired fan, a partial blockage, or a change under the slab such as a new water table. Either way the system is not doing its job, and the reading is worth checking whenever passing the pipe.
Why fans fail, and when
Radon fans are continuous-duty motors that live in attics and on exterior walls through Nebraska summers and winters. Most run reliably for five to ten years; bearings and windings wear, and the failure is usually a stop rather than a gradual fade. A fan that has started humming louder, rattling or cycling is on its way out.
Other causes of a zero reading are more mundane: a tripped GFCI or breaker on the fan circuit, a disconnected cord after attic work, ice or a bird nest at the discharge, or condensation pooled at a low point in the pipe. A repair visit runs through those before replacing anything.
- Breaker or GFCI tripped: reset once; if it trips again, the fan has a fault.
- Pipe blocked at the discharge: ice, nests, debris; the fan runs but pulls nothing.
- Condensation trap: a horizontal or sagging pipe run holding water; the installation needs correction.
- Fan failed: the common case after year five; replacement is a like-for-like swap on the same pipe.
What the house is doing in the meantime
With the fan stopped, the house returns to whatever it read before mitigation, and in the heating season it can read higher, because the suction point and pit are now open paths to the soil. The sealing work still helps a little; the pressure difference that did the real work is gone.
That is why a stopped system is a same-week repair, not a someday item, and why a radon test after the repair is not optional. The retest is what confirms the number, not the sound of the fan.
What a repair visit checks
A licensed technician confirms power at the fan, inspects the discharge and the pipe route, checks every joint and the sump lid for leaks, and measures suction at the manometer against the install label. If the fan is the fault, the replacement is matched to the pipe diameter and the original design suction, not simply the loudest unit on the truck.
The visit also catches installation problems that an original crew may have left: a fan mounted in a basement, a discharge below a window, a missing label. Those get corrected because they are safety items, not upgrades.
After the fix
Nebraska requires the retest to be performed by a licensed measurement business, and the timing is the same as for a new install: at least 24 hours after the fan restarts, within 30 days. The result goes in the house file with the original post-mitigation test and becomes the record the next buyer sees.
For a Lincoln homeowner who noticed the gauge sitting level, the sequence is short: check the breaker, call for the repair, retest. For radon system repair in Lincoln, that retest is the part that closes the loop.
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Quick Answers
How often should the manometer be checked?
A glance once a month is enough, and any time work is done in the attic or on the electrical panel. The reading should match the install label; a change in either direction is worth a call.
Can a failed radon fan be replaced with any fan?
No. Radon fans are sized to the pipe diameter and the soil conditions measured at install. An undersized fan leaves the far end of the slab without suction; an oversized one wastes power, adds noise and can pull conditioned air through the floor. The replacement should match the original design.
Is a radon system alarm worth adding?
An audible or electronic alarm that monitors pipe pressure removes the need to remember the gauge and is a modest add-on at replacement time. Continuous digital radon monitors in the living space are another option and give the actual reading rather than the fan status.