What to Expect on Radon Mitigation Installation Day

Before the Contractor Arrives

Clear the work area. The contractor needs access to your lowest foundation level. For a basement, clear 3–4 feet around the perimeter walls. For a crawl space, they'll need clear access to the entry point.

Know where your utilities run. HVAC ducts, water lines, and electrical runs all affect where the suction pipe can be routed. You don't need to mark them — the contractor will assess — but if you know of any unusual routing, mention it.

Plan for a full day. Most residential installations take 4–8 hours. A standard slab job is closer to 4 hours. A crawl space job or complex routing can stretch to 8. Plan to be home.

The Assessment (First 30–60 Minutes)

The contractor walks your foundation before touching anything. They're looking for:

Sub-slab communication: The best suction point is where one hole will depressurize the largest area of slab. The contractor tests this with a vacuum applied to a small exploratory hole — they can feel how the pressure extends through the aggregate.

Pipe routing options: The most direct path to the exterior or attic, avoiding finished walls and structural elements where possible.

Radon entry points: Cracks in the slab, floor-wall joints, sump pit openings, utility penetrations. These get sealed as part of the installation.

Fan size and location: Based on sub-slab conditions and radon levels, the contractor selects the appropriate fan (see our RadonAway fan comparison guide).

The Installation

Core drilling: One or more 3"–4" holes are drilled through the slab at the selected suction points. This takes 10–20 minutes per hole. It's loud but not structural — the holes are filled around the pipe.

Suction test: Before committing to the pipe route, the contractor often does a quick vacuum test to confirm the suction point is effective.

Pipe run: PVC pipe (usually 3") is run from the suction point through the path of least resistance to the exterior or attic. Through interior walls, this may mean drilling through floor joists and running pipe in a utility chase.

Fan installation: The fan is mounted in the attic, on an exterior wall, or in the garage. It can't be in conditioned living space (noise and backdrafting concerns). The contractor wires it or installs a cord-and-plug setup per local code.

Sealing: The slab penetration is sealed around the pipe with hydraulic cement or epoxy. Other visible radon entry points (cracks, floor-wall joints, sump cover) are sealed.

Warning device: A manometer (a U-shaped liquid-filled gauge) is installed on the pipe in a visible location. It shows you if the fan stops working — if the liquid levels equalize, the system isn't drawing suction.

What You'll See When It's Done

• A 3"–4" PVC pipe exiting through your basement wall, garage, or attic
• The pipe terminates at least 12 inches above any window or door opening (code requirement)
• A continuously running fan (quiet — about 35 dB, like a refrigerator hum)
• A manometer mounted on the pipe in the basement, showing unequal fluid levels (this is good — it means suction is working)
• A label or sticker on the system with the contractor's contact info and installation date

The Post-Installation Test

A follow-up radon test is placed within 24–48 hours of installation. Most contractors use a 48-hour short-term charcoal canister. Some use electronic continuous monitors.

Expected results: A properly installed sub-slab depressurization system typically reduces radon levels by 80–99%. For a home that tested at 6 pCi/L, a post-install result of 0.8–1.2 pCi/L is typical.

If the result is still above 4 pCi/L: The contractor should return, at no extra charge, to diagnose and adjust the system. This sometimes means adding a second suction point, upgrading the fan, or finding additional entry points that weren't sealed.

After Installation

Annual check: Every spring, look at your manometer. If the fluid levels are equal, the fan may have stopped. Call your contractor.

Retest every 2 years: Even working systems can experience changes in sub-slab conditions. A $25 long-term alpha track test gives you peace of mind.

Fan replacement: Fans last 5–15 years. When yours dies, a replacement fan costs $100–$250 and takes 30 minutes to swap. Your contractor can do it, or you can DIY it if you're comfortable with the system.

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