Radon Fan Not Working? Signs, Causes and Costs
How to tell a radon fan has stopped, what the U-tube gauge is telling you, what usually fails, and what EPA says a fan replacement costs.
A radon mitigation system only works while its fan runs. EPA's Consumer's Guide is blunt about it: the fan "should NEVER be turned off; it must run continuously for the system to work correctly." When the fan stops, the space under the slab is no longer held at lower pressure, and radon levels can drift back toward where they were before the system went in.
EPA says fans may last five years or more, that manufacturer warranties tend not to exceed five years, and that replacing a fan cost around $200 to $350 including parts and labor in its 2010 guide (2010 dollars). We have not found a current published survey of fan replacement prices, so ask for a written quote and compare it with that older figure.
Signs the fan has stopped or is failing
- The system warning device shows a problem. EPA requires active systems to have one: a liquid gauge (often a U-tube manometer), a sound alarm, a light, or a dial gauge, placed where it can be seen or heard easily.
- The liquid levels in a U-tube gauge are even. A working fan holds one side higher than the other; even levels mean no suction in the pipe.
- No sound or vibration at the fan, which EPA says should sit outside or in an unoccupied attic, never in or below a living area.
- New grinding, rattling or humming. Worn bearings usually announce themselves before the motor stops.
- A retest that reads higher than the post-mitigation test did. EPA recommends retesting at least every two years even when nothing seems wrong.
What usually causes it
| What you notice | Likely cause | First check |
|---|---|---|
| Gauge even, fan silent | No power: tripped breaker, GFCI or switched-off outlet | Reset the breaker or outlet; EPA requires the fan circuit to meet local electrical code |
| Gauge even, fan running | Disconnected or cracked pipe, or a failed seal at the slab | Look along exposed pipe for a loose coupling |
| Fan noisy or vibrating | Worn bearings near the end of fan life | Note the install date; EPA says fans may last five years or more |
| Gauge reads, radon still high | System undersized or a new entry route | See the troubleshooting guide linked below |
| Gauge slowly drifting | Ice or debris at the exhaust, or water in the pipe | Have a mitigator inspect the exhaust and drain path |
Causes are the common failure points for a fan-and-pipe system; requirements and lifespans are from EPA's Consumer's Guide to Radon Reduction (2010).
What to do, step by step
- Step 1: Check power first. A tripped breaker or ground-fault outlet is the cheapest fix there is.
- Step 2: Read the gauge again after power is restored. If the levels split, the fan is pulling again.
- Step 3: If the fan has power but the gauge stays even, call the installer. EPA asks contractors to give written operating and maintenance instructions and copies of warranties; check whether the fan is still within its warranty, which EPA says tends not to exceed five years.
- Step 4: For a replacement, ask for a quote that names the fan model and its rated airflow, so the new fan matches what the system was designed around.
- Step 5: Retest. EPA recommends a post-mitigation test within 30 days but no sooner than 24 hours after a system is back in operation, with windows and doors closed for 12 hours before and during the test.
What it costs to run and to fix
In EPA's 2010 table, a sub-slab system's fan electricity and heated or cooled air loss came to $50 to $200 a year, a block-wall system $100 to $400 (2010 dollars). A fan replacement was about $200 to $350 with parts and labor. If the system needs more than a fan, for example a second suction point because levels are still high, price it in the radon mitigation cost calculator; HomeGuide's 2026 survey puts a whole new active system at $1,200 to $2,000.
Remodeling and fan problems
EPA warns that structural changes after a system is installed, such as finishing a basement, can affect how well it works and may void warranties. Ask the original mitigator before boxing in pipe or moving the fan, and retest in the lowest lived-in area after the work.
Questions
Can I turn the fan off in winter?
No. EPA says the fan must run continuously for the system to work.
Can I move the fan into the basement where it is quieter?
No. EPA's installation rules say the exhaust fan must not be in or below a livable area.
Who should replace it?
EPA recommends a qualified radon mitigation contractor, and several states require a state credential for paid radon work, including Pennsylvania and Ohio.
Related: radon still high after mitigation, radon mitigation methods compared, and the radon mitigation cost guide.
Sources
- EPA, Consumer's Guide to Radon Reduction (2010 edition, archived)
- EPA, A Citizen's Guide to Radon (2016)
- 25 Pa. Code Chapter 240, radon certification
- Ohio Administrative Code 3701-69-04
- HomeGuide, Radon Mitigation Cost (Feb 5, 2026), cited as text
Prices are published ranges from the sources listed on this page; anything we calculated is labeled as an estimate. Get at least two itemized bids from certified or licensed mitigators. Run the calculator to build your own range.