What Does a Radon Mitigation System Look Like?
Buyers touring a home often spot a white PVC pipe running up an exterior wall or through a garage and wonder what it is. More often than not, it is a radon mitigation system, and knowing how to recognize its parts tells you a lot about whether the home’s radon problem was handled properly. This guide summarizes EPA and Colorado state guidance current as of 2026 and is educational only; consult a certified radon professional for installation or evaluation decisions and your physician for health concerns. Below is a plain-language walkthrough of what a radon mitigation system looks like, where each component sits, and how to tell a quality installation from a sloppy one.
What does a radon mitigation system look like?
A typical active radon mitigation system looks like a continuous run of white or cream PVC pipe, usually 3 or 4 inches in diameter, that starts at the lowest level of the home (basement floor, crawl space, or slab) and runs upward to discharge above the roofline. Somewhere along that run sits an in-line fan, a bulging cylindrical or oval housing roughly the size of a coffee can, and a small clear U-shaped gauge called a manometer mounted on the pipe inside the home. Those three elements, pipe, fan, and gauge, are the visible signature of the most common system, active sub-slab depressurization.
The system is designed to be unobtrusive but is not hidden. The pipe may run inside through a closet or mechanical room and then outside, or it may run up an exterior wall. The point is to draw radon-laden soil gas from beneath the foundation and vent it harmlessly above the home. The explainer on how a radon mitigation system works covers the physics, and the Colorado radon testing guide explains why so many Front Range homes have one.
There is also a less-common passive version that looks similar but has no fan. A passive system relies on the natural stack effect, warm air rising, to draw soil gas up the pipe and out the roof. Many newer Colorado homes are built with passive radon-resistant features as a rough-in: a pipe routed from beneath the slab to the roof, ready to have a fan added if testing shows it is needed. If you see the pipe but no fan and no manometer, the home likely has a passive system, which is worth testing because passive systems are less reliable than active ones at reaching low radon levels.
The main components, part by part
The suction point and pipe
The system begins where the pipe penetrates the slab, crawl-space membrane, or sump pit. This suction point is sealed so the fan can pull soil gas from beneath the foundation rather than air from the room. From there the pipe runs vertically. Inside the home it is often boxed or routed through a utility space; outside it runs up the wall to the roof. A 3-to-4-inch diameter is standard.
The fan
The in-line radon fan is the heart of an active system. It is a sealed electric fan, mounted in the pipe run, that creates continuous suction. Crucially, it must be located outside the living space, in an attic, garage, or on the exterior wall, never in a basement below living areas, so that if the pressurized section ever leaks, radon does not vent back into the home. The fan runs 24/7 and hums quietly. The overview of radon exhaust fans covers how they are rated and sized.
The manometer (pressure gauge)
The manometer is a small clear plastic U-tube partially filled with colored liquid, mounted on the pipe inside the home. When the fan is running and creating suction, the liquid columns sit at different heights. If the columns are level (equal), the fan has likely failed. This simple gauge lets a homeowner confirm at a glance that the system is working, no electronics required.
The roofline discharge
The pipe terminates above the roof, typically extending a foot or more above the surface and located away from windows, doors, and air intakes so the discharged radon disperses into the open air rather than re-entering the home. The discharge point is part of why proper routing matters. The detailed look at the radon pipe explains routing and discharge requirements.
Where the system is installed
Placement depends on the foundation and the home’s layout. In a basement home, the suction point is usually cut into the slab, and the pipe runs up through an interior chase or out through the rim joist and up the exterior wall. In a crawl-space home, the installer first lays a sealed vapor barrier (sub-membrane depressurization) and draws suction from beneath it.
The two common configurations are interior systems, where the pipe and fan run up through the house and out the roof, often considered tidier and less weather-exposed, and exterior systems, where the pipe runs up an outside wall with the fan mounted outdoors. Both are legitimate when installed correctly. Front Range homes, with their prevalence of deep finished basements, frequently use slab suction points. The explainer on the radon vent covers the venting paths in more detail.
What you see depends on which configuration was chosen. With an interior system, the most visible part inside the home is the white pipe descending into the basement floor or sump and the manometer mounted on it, while the fan sits unseen in the attic. With an exterior system, the pipe and the bulging fan housing are visible running up an outside wall, often on a less-prominent side of the house. Neither is better than the other when done to standard; installers choose based on the home’s layout, the homeowner’s aesthetic preference, and the most efficient route to the foundation.
How to tell a good installation from a bad one
The visible components reveal a lot about installation quality. A quality system shows these traits:
- Fan located outside the living space (attic, garage, or exterior), never in a basement below living areas.
- Discharge above the roofline and away from windows, doors, and intakes.
- A working manometer with offset liquid columns confirming suction.
- Sealed suction point and sealed major entry routes (sump lids, visible foundation cracks).
- A label identifying the system, installer, and date, as required by standards.
- A documented post-installation test proving radon dropped below 4.0 pCi/L.
Warning signs include a fan mounted in the basement, a pipe discharging at ground level or near a window, a level (failed) manometer, or no record of a confirming test. The guidance on radon system maintenance explains how to keep a good system performing.
What it means when buying a home with a system
Seeing a radon mitigation system on a home for sale is reassuring, not alarming, it means a previous radon problem was addressed. Still, verify a few things before relying on it. Ask for the installation paperwork, the post-mitigation test result, and the fan warranty. Confirm the manometer shows the fan is running. Then have a current radon test performed during the inspection, because a system’s performance can drift over years and the only proof it still works is a fresh reading.
A system also has a finite-life component: the fan typically lasts 5 to 10 years before replacement. Factor that minor future cost into the purchase. The explainer on buying a house with a radon system walks through the buyer’s checklist.
How to read the system as a quick inspection
Once you know the parts, a 60-second visual check tells you a lot. Walk to the lowest level and find where the pipe enters the floor or sump; confirm the penetration is sealed, not just resting in an open hole. Locate the manometer and confirm the colored liquid columns are offset, proof the fan is pulling suction. Trace the pipe’s path: it should rise continuously without sagging low spots that could collect condensation, and the fan should be in the attic, garage, or outside, never in the basement living area. Step outside and confirm the pipe discharges above the roofline, away from windows and the front facade.
If any of those checks fail, a level manometer, a fan in the basement, a discharge at ground level, or an unsealed suction point, the system may be non-functional or improperly installed, and a current radon test plus a professional evaluation is warranted. The explainer on radon removal covers what proper performance looks like.
The bottom line for buyers and owners
A correctly installed, well-maintained system that tests below the action level is a genuine asset, evidence the home’s radon is under control rather than a hidden liability. Recognizing the parts and knowing what good looks like turns that white PVC pipe from a mystery into a quick due-diligence check. For Front Range buyers in particular, where elevated radon is common, a visible mitigation system is reassuring rather than alarming, provided the paperwork, the manometer, and a fresh test all confirm it is doing its job. The components are simple enough that any homeowner can learn to verify them, which is the best protection against both a failed system and an unnecessary worry.
References
- Consumer’s Guide to Radon Reduction — U.S. Environmental Protection Agency
- Radon Mitigation Systems in Colorado — Colorado Department of Public Health and Environment
- Reducing Radon in Your Home — American Lung Association
Front Range buyers who want a radon system evaluated or a current test before purchase can reach a vetted local professional through our contact page.
Radon mitigation fans & parts
If a sub-slab depressurization system is the fix, the inline fan is the heart of it. Match the fan to your soil and pipe diameter — or have a certified installer size it.
| Product | Why | Buy |
|---|---|---|
 RadonAway RP145 Inline Fan | Common 4-in. SSD workhorse fan. | Amazon — $152.00 |
 Fantech Rn2 Radon Fan | Quiet operation; energy-efficient. | Amazon — $148.29 |
 Radon U-Tube Manometer | Confirms the system is pulling suction. | Amazon — $10.99 |