How to Install a Radon Mitigation System: Steps
Learning how to install a radon mitigation system means understanding a sequence of well-defined steps: locating a suction point under the slab, cutting through the foundation, routing a sealed pipe to above the roofline, adding a continuously running fan, and sealing the openings that would otherwise undermine the system. For Front Range homeowners facing elevated radon, knowing the process clarifies what a contractor will do — or what a careful DIY attempt demands. This guide walks through each step and summarizes EPA and Colorado state guidance current as of 2026; consult a certified radon mitigation professional for decisions specific to your home.
How to Install a Radon Mitigation System: The Core Steps
The standard residential method is active sub-slab depressurization (ASD). The principle is to create lower pressure beneath the concrete slab than in the home above it, so radon gas is captured under the foundation and vented outdoors instead of rising into living space. Achieving that takes five main steps: assess the foundation and choose a suction point, cut and excavate the suction pit, install and seal the vent pipe, mount the fan and manometer, and seal the foundation. Each step builds on the last, and skipping or rushing any one compromises the whole system.
Before any installation, the home should be tested to confirm radon is elevated and to establish a baseline. The radon testing guide for Front Range homeowners explains how that initial measurement informs the install.
Step 1: Assess the Foundation and Choose the Suction Point
The first step is diagnostic. The installer identifies the foundation type — full basement, slab-on-grade, crawl space, or a combination — because each calls for a slightly different approach. A basement or slab home usually gets a sub-slab suction point; a crawl space typically uses sub-membrane depressurization, where a sealed plastic membrane is laid over the soil and air is drawn from beneath it.
Choosing the suction point well is critical. The goal is a location where the fan’s pull can spread under as much of the slab as possible, often aided by the gravel layer beneath the foundation. A poorly placed suction point may leave parts of the slab undepressurized, letting radon continue to enter. This is one of the judgment calls that separates a competent install from a guess, as the guide on how a radon mitigation system works explains.
Step 2: Cut and Excavate the Suction Pit
Once the point is chosen, the installer cuts a hole roughly four to six inches in diameter through the slab using a core drill or hammer. Beneath the opening, several gallons of soil or aggregate are removed to create a small pit. This void acts as a plenum, allowing the fan to draw air from a wider area under the foundation rather than just the immediate hole. The size of the pit influences how effectively suction spreads, especially in homes with tightly packed sub-slab material.
Step 3: Install and Seal the Vent Pipe
A three- or four-inch PVC pipe is set into the suction point and sealed airtight to the slab with polyurethane caulk or a comparable sealant. From there the pipe is routed up and out of the conditioned space along one of two paths. An interior route runs the pipe through a closet or chase, into the attic, and out through the roof. An exterior route brings the pipe up the outside wall to above the eaves. Either way, the discharge must terminate above the roofline, away from windows, doors, and air intakes so vented radon cannot re-enter. Joints are glued and the run is supported to prevent sagging that could trap condensation. The article on the radon vent pipe covers routing choices in depth.
Step 4: Mount the Fan and Manometer
The inline radon fan is the active element. It is installed in the pipe run within an unconditioned space — the attic or the exterior — never inside the living area, because the section of pipe downstream of the fan is under positive pressure, and any leak there should vent outside rather than into the home. The fan is sized to the home’s needs; an undersized fan fails to depressurize the slab, while an oversized one wastes energy.
A U-tube manometer is mounted on the pipe below the fan to give a visible suction reading. Once the fan is wired to a dedicated, continuously powered circuit and switched on, the manometer should show unequal liquid levels, confirming the system is pulling air. The guide on radon exhaust fans explains fan sizing and types.
Step 5: Seal the Foundation
The final installation step is sealing. The installer caulks visible cracks in the slab and foundation walls, seals around the suction-point penetration, and covers any sump pit with an airtight lid fitted with a gasket. Sealing matters because every unsealed opening lets the fan draw conditioned indoor air instead of sub-slab soil gas, reducing the suction available to capture radon. Thorough sealing makes the system more effective and more energy-efficient.
Step 6: Test, Verify, and Document
Installation is not finished until the system is verified. After the fan has run long enough to stabilize — typically at least 24 hours — a follow-up radon test confirms the level has dropped below the EPA action level of 4.0 pCi/L. If it has not, the installer may add a second suction point, upsize the fan, or seal additional openings. The installer should label the system with the date and baseline manometer reading, and provide the homeowner with the test results.
From there, ongoing care is light: glance at the manometer periodically, listen for the fan, and retest at least every two years or after any fan replacement. For those weighing whether to attempt the work themselves, the guide on DIY radon mitigation lays out the realities, and many homeowners conclude that the diagnostic skill and verification a certified contractor brings are worth the cost.
Why Professional Installation Often Wins
The steps above are clear, but several depend on judgment and tools the average homeowner lacks: where to place the suction point, how to size the fan, and how to confirm the system actually works. A system that runs continuously but fails to lower radon offers false reassurance, which is worse than no system. Certified mitigation contractors follow established standards, carry diagnostic equipment, and stand behind verified results — which is why, for most Front Range homes, professional installation is the dependable route to clean indoor air.
Tools and Materials the Job Requires
The installation calls for specific tools and materials, and the list itself signals the scope of the work. Cutting the suction point requires a rotary hammer or core drill capable of penetrating concrete. The vent system uses schedule-40 PVC pipe, typically three or four inches in diameter, with elbows, couplings, and pipe straps to route and support it. Polyurethane caulk or a comparable sealant bonds the pipe to the slab and seals cracks. The fan is an inline radon-rated unit sized to the home, wired to a dedicated circuit, and a U-tube manometer provides the suction readout.
Roof penetration requires appropriate flashing to keep the exhaust weather-tight, and any electrical connection must meet code, which in many jurisdictions means a licensed electrician for the fan circuit. Assembling this list makes clear why the job, though achievable in a day, is not a casual project: it combines concrete work, plumbing-style pipe assembly, roofing, and electrical, each with its own requirements for doing it safely and to standard.
Common Installation Mistakes
Several recurring errors separate a working system from one that disappoints. Placing the suction point poorly is the most consequential — if the fan’s pull cannot spread under the slab, parts of the foundation remain undepressurized and radon keeps entering. Undersizing the fan leaves the system unable to draw enough soil gas, while leaving foundation cracks and the sump pit unsealed lets the fan waste its capacity pulling conditioned indoor air instead.
Improper exhaust placement is another frequent mistake. An exhaust that terminates below the roofline, too close to a window, or near an air intake can allow vented radon to re-enter the home, defeating the purpose. Installing the fan inside the living space rather than in an unconditioned attic or exterior run is a safety error, since any leak in the pressurized section would discharge radon indoors. Finally, skipping the post-installation test leaves the homeowner with no proof the system actually lowered radon. Avoiding these mistakes is exactly what experience and certification buy.
After Installation: Verification and Care
The work is judged by results, and verification is the final and non-negotiable step. After the fan has run long enough to stabilize, a follow-up radon measurement confirms the level has dropped below the EPA action level of 4.0 pCi/L. If the first attempt falls short, the fix is usually adding a suction point, upsizing the fan, or sealing additional openings, followed by another test. Once confirmed, the system needs only light ongoing care: periodic manometer checks, an occasional listen for the fan, and a retest at least every two years or after any fan replacement or major home change. Documenting the installation date, baseline manometer reading, and every retest result gives the homeowner a clear maintenance record and reassures future buyers that the system has performed as intended.
How Long the Job Takes and What It Costs
A standard active sub-slab installation is typically completed in a single day, often within a few hours for a straightforward basement or slab home. More complex jobs — multiple suction points, mixed foundations, or difficult routing through a finished home — take longer. Professional installation generally runs between $800 and $2,500, with the typical figure landing around $1,200 to $1,800, driven by foundation type, pipe length and routing, and the number of suction points required.
Ongoing costs are modest. The fan runs continuously and adds a few dollars a month to the electric bill, and it eventually needs replacement every 5 to 10 years at a cost of a few hundred dollars. Against these figures sits the value: a system that reliably keeps a home below the EPA action level of 4.0 pCi/L, reducing a documented lung-cancer risk. For Front Range homeowners in particular, where elevated radon is widespread, the cost-to-benefit ratio strongly favors getting the work done correctly the first time.
Crawl Spaces and Special Cases
Not every home fits the textbook sub-slab model, and the installation adapts to the foundation. Crawl-space homes use sub-membrane depressurization: a heavy polyethylene membrane is sealed over the exposed soil, and the fan draws radon from beneath that barrier rather than from under a slab. The membrane must be carefully sealed at the edges and around piers to perform, which makes thorough installation as important here as slab sealing is in a basement.
Homes with a mix of basement, slab, and crawl space may need more than one suction point or a combination of techniques to cover the entire footprint. Older homes with fieldstone or rubble foundations present the hardest cases and sometimes require creative approaches a general homeowner is unlikely to engineer correctly. These special cases are where the diagnostic skill of an experienced, certified installer pays off most clearly, and they are a strong argument against attempting a DIY installation on anything but the simplest foundation. Matching the method to the foundation is what makes the difference between a system that controls radon and one that merely runs.
References
- Consumer’s Guide to Radon Reduction — U.S. Environmental Protection Agency
- Colorado Radon Mitigation Standards — Colorado Department of Public Health and Environment
- Radon and Lung Health — American Lung Association
Front Range homeowners planning a radon system installation can reach out through our contact page to connect with a certified local mitigation professional.
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 |