This is the complete step-by-step guide to installing a radon mitigation system — written for homeowners who want to understand every action a certified mitigator takes, whether to supervise the job intelligently, verify the work afterward, or research whether to attempt a DIY installation.
Before You Start: What a Proper Installation Requires
A residential Active Sub-Slab Depressurization (ASD) system — the standard radon mitigation method for slab-on-grade and basement homes — requires:
- Rotary hammer drill with 3.5″–4″ concrete core bit
- 3″ Schedule 40 PVC pipe (quantity depends on routing length)
- PVC elbows, couplings, primer, and solvent cement
- Radon mitigation fan (sized to your home’s sub-slab conditions)
- U-tube manometer (system performance indicator)
- Hydraulic cement or non-shrink epoxy grout
- Polyurethane caulk and caulk gun
- Pipe straps and anchors
- Weatherproof discharge cap
- Shop vacuum for dust and diagnostic testing
Step 1: Conduct the Sub-Slab Diagnostic Test
Every properly executed installation begins with a diagnostic — not a drill. AARST-ANSI standard SGM-SF requires the mitigator to confirm sub-slab conditions before selecting the system design.
Drill a 2″ test hole through the slab at the proposed suction point location. Connect a shop vacuum or vacuum gauge to the hole and apply suction. Observe:
- Air draw from distant locations: Good aggregate communication — one suction point will likely cover the full slab
- Minimal draw: Dense fill (sand, clay) — may require additional suction points or higher-flow fan
- Water presence: Adjust pipe depth and consider sump connection integration
Do not proceed to Step 2 without completing this test. Installing a fan-sized-to-guess without knowing sub-slab conditions is the most common source of post-installation failures.
Step 2: Select the Suction Point Location
Based on the diagnostic, choose the final suction point location. Ideal characteristics:
- Central to the slab area to maximize suction field radius
- Adjacent to an interior wall cavity that routes to the attic
- Near an electrical outlet for fan power (or where running a new circuit is feasible)
- Out of finished living space where possible (utility room, mechanical closet, unfinished basement corner)
Step 3: Core Drill the Slab
Use the rotary hammer with a 3.5″ or 4″ diamond-tipped core bit. Drill through the slab — depth varies from 3.5″ for standard residential slabs up to 6″ for thick commercial-grade pours. Keep the shop vacuum running simultaneously to capture concrete dust.
After the core is complete, use the vacuum to clear all debris from the hole and the immediate sub-slab cavity. A clean core hole produces better airflow and allows proper grout sealing later.
Step 4: Plan and Cut the Pipe Route
Trace the pipe path from the core hole to the attic (interior routing) or through the foundation wall (exterior routing). Mark all penetration points through:
- Bottom wall plate (where pipe enters wall cavity)
- Top wall plate (where pipe exits wall cavity into attic)
- Any fire-rated floor/ceiling assemblies (requires firestop caulk)
Use a hole saw sized to the pipe diameter plus 1/4″ clearance. Cut all penetrations before beginning pipe assembly.
Step 5: Assemble and Install the Riser Pipe
Begin at the slab and work upward. Cut pipe sections to length. For each joint:
- Apply PVC primer to both surfaces (pipe and fitting socket)
- Apply PVC cement immediately after primer — do not let primer dry
- Push pipe into fitting with a quarter-turn and hold for 30 seconds
- Wipe excess cement from the joint
Dry-fitting PVC without cement is not acceptable on a radon system. Any joint leak allows air to enter the system at that point, reducing suction at the sub-slab where it is needed.
Strap the pipe to framing with pipe hangers every 4–6 feet. Pipe should be plumb or have positive slope toward the suction point (no water traps).
Step 6: Mount and Connect the Radon Fan
Install the radon fan in the attic or on the exterior wall — never inside conditioned living space. Fan placement requirements:
- Must be downstream of all pipe connections from the slab (i.e., the fan pulls, not pushes)
- Fan inlet connects to the riser pipe from below
- Fan outlet connects to the discharge pipe going out and up
- Fan is secured with straps or a mounting bracket to prevent vibration movement
Wiring: the fan connects to a dedicated 120V circuit or outlet. Many residential installations use a standard grounded outlet within reach. Some jurisdictions require hardwired installation — confirm local code requirements before proceeding.
Step 7: Install the Discharge Pipe and Termination Cap
From the fan outlet, run the discharge pipe out through the roof or gable end and terminate with a weatherproof cap. AARST SGM-SF termination requirements:
- Discharge must extend at least 12 inches above the roof surface at the point of penetration
- Discharge must not terminate within 10 feet of any window, door, or ventilation opening measured horizontally
- The cap must prevent rain and pest entry
If routing through the roof, use a standard 3″ plumbing pipe boot flashing. If routing through the gable, use a PVC elbow and exterior wall cap. Both are AARST-compliant when termination height requirements are met.
Step 8: Seal the Core Hole and Slab Cracks
Return to the core hole at the slab. The riser pipe is now in place. Use hydraulic cement or non-shrink epoxy grout to fill the annular gap between the pipe and the concrete edge. Apply in layers if the gap is large — hydraulic cement sets fast in thin applications.
After the core hole is sealed, inspect the slab for:
- Control joints and expansion joints (fill with polyurethane backer rod + caulk)
- Visible cracks (fill with polyurethane caulk)
- Floor-wall joint gap (caulk around the full perimeter in the mitigation zone if accessible)
- Any pipe or conduit penetrations through the slab (seal with hydraulic cement or foam + caulk)
Sealing quality directly determines post-mitigation results. A system with a 20-watt fan and excellent sealing will often outperform a system with a 90-watt fan and poor sealing.
Step 9: Install the System Performance Indicator
Install a U-tube manometer on the riser pipe at a visible interior location — typically at the base of the riser pipe at eye height. The manometer connects to a small hole drilled in the pipe and sealed with the supplied fitting.
When the system is running correctly, the colored liquid in the U-tube will be displaced (one side higher than the other), indicating negative pressure in the pipe. A level liquid column means the fan is not generating suction — an alert to inspect the system.
Step 10: Apply Required Labels and Power On
AARST SGM-SF requires permanent labeling on the system pipe identifying it as a radon reduction system, including installer credentials and installation date. Apply the label at a visible location on the riser pipe, typically near the manometer.
Power on the fan. Confirm the manometer shows displacement. Use a digital pressure gauge at the suction point to confirm the system is generating measurable negative pressure (typically 0.02–0.15 inches of water column at the slab, depending on aggregate conditions).
Step 11: Conduct Post-Installation Testing
The system is now mechanically complete. Place a short-term radon test device (48-hour charcoal canister or continuous monitor) in the lowest habitable level of the home under closed-house conditions. Wait the full 48 hours before retrieving the test. Mail the charcoal canister to the lab and await results (typically 3–7 business days).
EPA target: below 4.0 pCi/L. Most properly installed systems achieve 0.5–2.5 pCi/L regardless of initial levels, provided sealing was thorough and the fan is correctly sized.
Common Installation Mistakes to Avoid
- Skipping the diagnostic: Drilling without testing sub-slab conditions leads to undersized or incorrectly placed suction points
- Fan inside conditioned space: If the fan casing leaks, radon is discharged inside the home
- Dry-fitted PVC: Joints without cement will eventually separate
- Foam-only core seal: Foam compresses over time; hydraulic cement is the correct material
- Discharge below roofline: Radon can re-enter through adjacent windows
- No manometer: Required by AARST; without it, a failed fan goes undetected
- Multiple test holes without sealing unused ones: Every open test hole is an uncontrolled radon entry point
Frequently Asked Questions
How many steps does radon mitigation installation involve?
A standard ASD installation involves 11 steps: diagnostic test, suction point selection, core drilling, pipe route planning, pipe assembly and installation, fan mounting, discharge pipe and cap installation, slab sealing, manometer installation, labeling and power-on, and post-installation radon testing.
What size PVC pipe is used for radon mitigation?
Most residential installations use 3-inch Schedule 40 PVC. High-flow applications with dense sub-slab fill or multiple suction points may use 4-inch pipe. The mitigator selects pipe size based on the diagnostic airflow test.
Can I install a radon mitigation system myself?
DIY radon mitigation is legal in most states for owner-occupied residences. The work requires concrete core drilling equipment (rentable), basic PVC plumbing skills, and a radon fan (available online). However, many states require licensed contractor installation for real estate transactions and warranty coverage. See our complete guide on DIY vs. professional installation.
How deep does the hole need to be for radon mitigation?
The core hole depth equals the slab thickness plus any sub-slab vapor barrier. Standard residential slabs are 3.5″–5″ thick. The core bit penetrates through the full slab depth to reach the sub-slab aggregate — the pipe connects to the void space below the concrete, not just the concrete itself.
How do I know if my radon mitigation system is working after installation?
Three verification methods: (1) the U-tube manometer shows displaced liquid, confirming negative pressure; (2) a digital pressure gauge reads measurable suction at the slab connection; (3) a post-mitigation radon test (48 hours minimum, closed-house conditions) shows levels below 4.0 pCi/L. All three should be completed for full confidence.
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