If the fluid in your U-tube gauge has gone level, your system has stopped pulling and your basement is on its way back to whatever the original number was. Most of the time it is the fan. Sometimes it is not, and the difference is worth five minutes of checking.
Radon fans run continuously, 24 hours a day, for years. They are simple, reliable, and they eventually wear out. When one fails, the system stops working immediately and silently — there is no smell, no alarm on most older installs, and no way to tell from inside the house except by looking at the gauge. Homes routinely sit for months with a dead fan before anybody notices.
The fix itself is straightforward. A fan swap is a small job compared to installing a system from scratch, and a properly matched replacement restores the original performance. The part that requires judgment is confirming that the fan is actually the problem, because a pressure loss can also come from a cracked pipe, a failed seal, a blocked discharge, or a change to the house that altered how it moves air.
Check this first: find the clear U-shaped tube taped to your radon pipe. If the colored fluid sits at the same height in both legs, the system is not pulling. If one side is clearly higher than the other, the fan is still doing work and your problem is elsewhere. Either way, call (218) 520-9679 and we will sort out which.
Every properly installed Minnesota system has one, usually mounted at eye level on the vertical run of PVC in the basement or garage. It is a clear plastic tube bent into a U, partly filled with dyed oil or water, with one leg open to the room and the other tapped into the pipe.
The fan pulls a vacuum inside the pipe. That vacuum lifts the fluid on the pipe side and drops it on the room side, so the two levels sit at different heights. The offset between the two columns is the reading. Most residential systems show somewhere between 0.5 and 2.0 inches of offset, though the correct value for your house is whatever the installer marked on the gauge or wrote on the system label at commissioning.
If your system has a digital pressure gauge or an audible alarm module instead of a U-tube, the same logic applies. Those devices monitor pipe pressure and warn you — with a light, a beep, or both — when the reading falls below a set threshold. They are worth adding during a fan replacement if you do not have one, precisely because the standard failure mode of a radon system is silent.
The EPA's guidance states that radon fans may last five years or more and that manufacturer warranties tend not to extend beyond five years. Industry sources put average service life somewhat higher, on the order of eight years of continuous operation. Either way, a fan is a wear item on a system that is otherwise permanent. If your system was installed with the house sale a decade ago and nobody has looked at it since, the fan is at or past its expected life.
Failure usually arrives one of three ways:
Noise is the complaint that brings most people to this page, and not all of it means the fan is dying.
A sudden high-pitched whine or grinding is bearing failure and means replacement. It will not get better and it usually gets loud enough to hear through a floor.
A low hum or buzz that transmits through the structure is often mounting, not the fan. Rigid PVC bolted tight to framing turns the whole house into a soundboard. Adding flexible rubber couplings on both sides of the fan, isolating the pipe from joists with resilient clamps rather than hard straps, and making sure the fan is not resting against sheathing will usually take care of it.
An intermittent rattle or gurgle is frequently water. Condensate that cannot drain back to the suction point pools in a low spot in the pipe and gets pushed around by the airflow. The cure is repitching the run so it drains continuously toward the suction point, which is how it should have been installed to begin with.
A whistle is usually air moving through a small leak — a failed joint, a cracked fitting, a loose fan coupling — and it is worth chasing, because that leak is also costing you suction.
Duluth's climate puts stress on radon systems that milder places do not. Soil gas leaving the house is warm and humid; the discharge pipe above the roofline is not. Moisture condenses on the inside of that cold pipe all winter.
Normally that condensate simply runs back down the pipe and into the suction pit, which is why the entire run has to be pitched properly. Where it goes wrong is when a section of pipe was installed level or slightly backwards, or when an exterior run is exposed to enough cold that condensate freezes before it can drain. Ice narrows the pipe, the fan works harder against the restriction, the manometer reading climbs, and in bad cases the discharge partially blocks.
The other cold-weather item is the fan location. Minnesota installations put the fan in an unconditioned space — attic or garage, never a living area — so that any leak downstream of the fan discharges outside the building envelope rather than into it. An attic fan in Duluth lives in genuinely cold conditions for months at a time, which is normal and by design, but it means insulation contact, ice buildup on the housing, and a properly sealed attic penetration all deserve a look during service.
A fan replacement is a small fraction of a new system. The EPA's published estimate for replacing a radon fan is roughly $200 to $350 including parts and labor. That figure comes from national consumer guidance and is on the older side; actual quotes vary with fan model, how the fan is mounted, and how hard it is to reach an attic install in January. What stays true is the ratio — a full radon mitigation system in Minnesota typically runs $1,500 to $3,000 installed, so a fan swap is a minor expense against a system that is otherwise still doing its job. Our radon mitigation cost page breaks down what drives the larger number if you are comparing repair against replacement.
| Symptom | Most likely cause | What it usually takes |
|---|---|---|
| Manometer level on both sides, fan silent | Motor failure, tripped breaker, or unplugged fan | Check power first, then replace the fan |
| Loud sudden whine, still pulling | Bearing wear near end of life | Replace the fan |
| Offset smaller than it used to be | Fan losing capacity, or a new opening in the slab | Diagnose before replacing — may be a sealing issue |
| Offset larger than it used to be | Blocked or iced discharge, crushed pipe | Clear the obstruction, repitch the run |
| Hum transmitted through the house | Rigid mounting, no vibration isolation | Flex couplings and resilient hangers |
| Gurgling or sloshing in the pipe | Condensate pooling in a level section | Repitch so the pipe drains to the suction point |
| System fine but radon retested high | House change, cracked pipe, or failed seal | Full system diagnostic, not a fan swap |
Replacing a fan on a system that has a different fault wastes money and leaves the house high. These are the situations where the fan is innocent.
This is not optional and it is the step most often skipped. A new fan is a new set of performance characteristics. If the replacement is undersized for your soil, the system will run quietly and look correct on the gauge while leaving the house above the action level. If the fan died months ago, you also have no idea what the house has been doing in the meantime.
Wait at least 24 hours after the new fan is running, then run a short-term test under closed-house conditions. The EPA recommends retesting a mitigated home at least every two years regardless, so a fan replacement is a natural time to do it. Our radon testing page covers closed-house conditions and device placement. If you are servicing a system in a home you are about to sell, the result also becomes part of the disclosure record under the Minnesota Radon Awareness Act.
One more note on licensing: in Minnesota, anyone performing radon mitigation work in a building they do not own or lease must be licensed by the Minnesota Department of Health, and an electrical permit is required for the fan circuit. That applies to a replacement fan the same as it does to a new install. Ask for the license number.
Look at the U-tube manometer on the radon pipe. If the colored fluid sits at exactly the same height in both legs of the tube, there is no vacuum in the pipe and the system is not pulling. If one column is higher than the other, the fan is still doing work. You can also put a hand on the PVC below the fan — a running fan produces steady airflow noise and a faint vibration. Most radon systems fail silently with no alarm, which is why the gauge is worth a glance every month or two.
The EPA states that radon fans may last five years or more and that manufacturer warranties generally do not extend beyond five years. Industry sources put average service life around eight years of continuous operation. A radon fan runs 24 hours a day, every day, so it is genuinely a wear item on an otherwise permanent system. If your system was installed at the time of a home sale a decade ago and nobody has serviced it since, assume the fan is at or past its expected life and check the manometer.
It depends on the sound. A sudden high-pitched whine or grinding is bearing wear and means the fan is near end of life and should be replaced. A low hum or buzz that you feel through the floor is usually a mounting problem rather than a failing fan, and flexible couplings plus resilient pipe hangers normally fix it. Gurgling or sloshing is condensate pooling in a section of pipe that is not pitched to drain, which is corrected by repitching the run rather than swapping the fan.
The EPA's published estimate is roughly $200 to $350 including parts and labor, though that figure comes from older national consumer guidance and real quotes vary with fan model, mounting location, and access. What holds is the proportion: a complete radon mitigation system in Minnesota typically runs $1,500 to $3,000 installed, so replacing a fan on an otherwise sound system is a minor expense by comparison. Getting a written diagnosis before authorizing a replacement is worth doing, because a fan swap will not fix a cracked pipe or a failed seal.
Ice buildup is a real issue here. Warm, humid soil gas condenses inside the cold section of discharge pipe above the roofline, and if the run is not pitched to drain continuously back to the suction point, that condensate can pool and freeze. Ice narrows the pipe, the fan strains against the restriction, and the manometer reading climbs above normal. The fixes are repitching any level or backward-sloped section and correcting exterior runs that are more exposed than they need to be. A visible frost plume at the vent on a cold day is normal and means the system is moving air.
Yes. A replacement fan has its own performance curve, and an undersized one will look perfectly normal on the gauge while leaving the house above the action level. Wait at least 24 hours after the new fan is running, then run a short-term test under closed-house conditions. You also have no record of what the house was doing during however long the old fan was dead. The EPA recommends retesting a mitigated home at least every two years in any case, so a fan replacement is a sensible time to do it.
Tell us what the manometer is showing and what the fan sounds like, and we will tell you whether this is a fan swap or something else. We service existing systems of any brand or age, and every repair is followed by a confirmation test.