A radon mitigation system is a network of PVC pipes, a small electric fan, and a few sealing components that pull radon gas from beneath your home and vent it above the roofline. From the outside, the most visible part is a white PVC pipe running up an exterior wall or through the roof. From the inside, you might see a pipe running through a basement corner or utility closet. The whole setup is modest, roughly comparable in visual impact to a dryer vent or a plumbing stack.
The Basic Setup: Pipe, Fan, and Vent
The most common type of radon mitigation is called active soil depressurization. A hole is cored through the basement slab (or into the crawl space ground), and a PVC pipe, typically 3 or 4 inches in diameter, is inserted into the opening. This pipe connects to an inline fan that creates suction beneath the foundation, pulling radon-laden air up through the pipe and exhausting it outdoors above the roof.
The pipe route depends on your home’s layout. In an interior installation, the pipe runs vertically from the basement floor up through closets, utility chases, or garage space, then exits through the roof much like a plumbing vent. In an exterior installation, the pipe exits through the basement wall near ground level, runs up the outside of the house, and vents above the roofline. Exterior runs are more visible from the curb but avoid taking up interior space. The pipe is usually white PVC, though some homeowners paint it to match their siding.
Where the Fan Goes
The fan is the only powered component. It’s a cylindrical unit, roughly the size of a large coffee can, mounted inline with the PVC pipe. Building codes require the fan to be placed outside the living space, so it typically sits in an attic, in a garage, or mounted to the exterior pipe run outside the house. This placement ensures that if the fan housing ever develops a small leak, the escaping gas vents outdoors rather than into your home.
Most radon fans produce between 50 and 75 decibels of noise, roughly equivalent to a refrigerator hum or quiet conversation. When mounted in an attic, you’ll rarely hear it inside the house. Exterior-mounted fans can create a faint hum near windows. Loose mounting brackets or pipe connections tend to cause more noise than the fan itself, so a tight installation matters. Inline mufflers are available if noise becomes an issue.
What the Exhaust Point Looks Like
At the top, the pipe terminates above the roofline. Standards from the American Association of Radon Scientists and Technologists require the discharge point to be at least 1 foot above the roof surface at its highest penetration point. It also needs to be at least 10 feet from any windows, doors, or other air intake openings (or at least 2 feet vertically above them). This prevents the exhausted radon from being pulled back into the house.
On a roof, the pipe looks like any other plumbing vent, just capped with a screen or rain cap. On an exterior wall run, the pipe extends past the eave line and curves away from the house at the top. Either way, it’s a small visual addition that most people wouldn’t notice unless they were looking for it.
Crawl Space Systems Look a Bit Different
If your home has a dirt-floor crawl space instead of a poured slab, the system uses a slightly different approach called sub-membrane depressurization. An impermeable plastic membrane is laid over the entire crawl space floor and sealed at the edges and around any piers or posts. A suction pipe penetrates through this membrane and connects to the same type of fan-and-vent setup described above.
The membrane itself is a thick sheet of polyethylene plastic, usually white or clear, that covers the exposed earth. If you peek into your crawl space after installation, you’ll see a smooth plastic floor with sealed seams, a pipe emerging from it, and possibly some caulking or tape around the perimeter where the membrane meets the foundation walls.
The Small Details You’ll Notice Inside
A few smaller components are visible at the basement level. The hole in the slab is sealed around the pipe with caulk or expanding foam. Any visible cracks in the foundation floor or walls are also sealed to maximize the suction beneath the slab. Near the pipe, usually at eye level in the basement, you’ll find a U-tube manometer: a small, clear plastic tube shaped like the letter U and partially filled with colored liquid. This is your system’s health indicator.
When the system is running correctly, the liquid levels in the two sides of the U-tube will be uneven. The side connected to the suction pipe will show a higher fluid level, indicating that negative pressure exists beneath your slab. A reading between 0.5 and 1.75 inches of difference between the two sides means the system is pulling properly. If the liquid is level on both sides, the fan has stopped working or the system has lost suction. It takes about two seconds to glance at during a trip to the basement.
How Much Space It Takes Up
Inside, the pipe footprint is minimal. It’s a 3- or 4-inch pipe running along a wall or through a corner, often tucked behind a furnace or water heater. The floor penetration point takes up about the area of a small plate. If routed through interior closets, you lose a small corner of shelf space. Outside, the pipe hugs the wall and extends to the roof. The fan housing adds a slight bulge to the pipe run but isn’t much larger than the pipe itself.
Professional installation typically takes a few hours for a straightforward home. The installer cores through the slab, routes the pipe, mounts the fan, seals all penetrations, and tests the system. Most homeowners are surprised by how simple the finished product looks relative to what it accomplishes.
Cost, Lifespan, and Upkeep
The EPA reports that the average installation costs about $1,500, with a typical range of $900 to $3,000 depending on your home’s layout, foundation type, and local labor rates. Homes with complex foundations, multiple slabs, or difficult pipe routing fall on the higher end.
Once installed, the system requires very little maintenance. The fan runs continuously, and most units last about 20 years despite carrying only a 5-year manufacturer’s warranty. Your main upkeep task is checking the U-tube manometer periodically to confirm the system still has suction, and retesting your home’s radon levels every two years. Electricity costs for running the fan are modest, typically a few dollars per month.
What “Success” Looks Like on a Test
The EPA recommends mitigation when indoor radon reaches 4 pCi/L (picocuries per liter) or higher, and suggests considering it for levels between 2 and 4 pCi/L. The average American home sits at about 1.3 pCi/L, and outdoor air averages 0.4 pCi/L. A properly installed system typically brings levels well below 4 pCi/L, often down to 1 or 2 pCi/L. There is no known safe level of radon exposure, so the goal is to get levels as low as reasonably achievable.
After installation, your mitigator will likely recommend a follow-up radon test within 30 days and then periodic retesting to confirm the system continues to perform. The system itself doesn’t change over time in any visible way. It just sits there, quietly pulling soil gas from under your foundation and venting it where it dissipates harmlessly into the atmosphere.