Radon Mitigation System Service Call
One of our most popular services.
Many people don’t know if their radon systems are working properly or not.
If your radon system needs an evaluation, repair, or a thorough checkup, we have the solution.
This comprehensive diagnostic +50 point checklist is designed to troubleshoot active sub-slab depressurization (ASD) systems and identify radon entry pathways. We also offer specialized checklists for other system types and unique mitigation challenges.
1. Active Mitigation Fan & System Diagnostics
- U-tube manometer reading: Verify liquid levels are offset and record the pressure reading in inches of water column (WC).
- Fan power status: Ensure the fan is receiving electrical power and running continuously without interruption.
- Fan housing condition: Inspect the exterior fan housing for cracks, UV degradation, or water damage
- Fan vibration & noise: Check for excessive vibration, humming, or grinding noises indicating bearing failure.
- Fan sizing evaluation: Verify the fan model matches the current pressure and airflow needs of the soil.
- Electrical disconnect switch: Confirm a dedicated, weatherproof electrical disconnect switch is installed near exterior fans.
- Condensate bypass installation: Ensure the fan setup allows condensed water to drain past the fan impeller safely.
- Exhaust piping pitch: Check that all horizontal vent piping slopes back toward the suction pit to drain water.
- Exhaust stack height: Verify the vent discharge terminates at least 10 feet above ground level.
- Exhaust stack clearance: Confirm the exhaust is 10 feet away and 2 feet above any window, door, or opening.
- Exhaust termination cap: Check that the pipe end has a protective screen to block debris and pests without a restrictive cap.
- System labeling: Verify the vent pipe features prominent, clear labels marking it as a radon mitigation system.
2. Suction Pit & Sub-Slab Communication
- Suction pit depth: Check the depth and volume of the dug-out pit underneath the slab penetration.
- Aggregate check: Evaluate if the material under the slab is loose gravel, tight sand, or dense clay.
- PFE testing (Pressure Field Extension): Drill small test holes at distant slab points to measure sub-slab vacuum.
- Micromanometer verification: Use a digital micromanometer to confirm at least -0.025 water column inches at test holes.
- Suction pipe seal: Inspect the polyurethane sealant joint where the PVC pipe penetrates the concrete slab.
- Slab thickness assessment: Measure concrete slab thickness through test holes to evaluate structural resistance.
- Multiple suction points: Determine if interior footings require adding secondary suction points to bridge separated slab areas.
3. Concrete Slab & Foundation Wall Integrity
- Slab crack inspection: Map and check all visible floor cracks for active soil air leaks using a smoke pencil.
- Expansion joint sealing: Inspect the perimeter expansion joints where the slab meets the foundation walls for gaps.
- Control joint evaluation: Check all saw-cut control joints to ensure they are completely sealed with elastomeric sealant.
- Crawl space vapor barrier: Inspect membrane thickness (minimum 6-mil, preferably 30-mil) and verify it covers 100% of the soil.
- Vapor barrier seam tape: Confirm all crawl space membrane seams are overlapped 12 inches and taped securely.
- Vapor barrier wall attachment: Ensure the crawl space membrane is sealed to the foundation walls with polyurethane caulk or furring strips.
- Block wall top-caps: Inspect the top course of concrete block walls to see if they are open or sealed shut.
- Wall-to-floor joint leakage: Check for air bypass at the cove joint using chemical smoke or a thermal camera.
- Utility penetration seals: Inspect gaps around sewer lines, water mains, gas lines, and electrical conduits.
4. Drainage Systems & Sump Pump Basins
- Sump pit cover seal: Check that the sump basin has an airtight, gas-permeable gasketed lid.
- Sump lid view port: Ensure the sump cover features a clear, sealed window to inspect pump operation.
- Sump discharge pipe seal: Verify the rubber grommets or caulking around the pump discharge pipe are airtight.
- Sump power cord grommet: Check the seal around the electrical power cords exiting the sump basin.
- Sump pump check valve: Verify the check valve prevents backflow and does not cause excessive physical system vibration.
- Floor drain traps: Confirm all floor drains have active water traps or mechanical trap-seal devices (like Dranjer valves).
- Perimeter French drain isolation: Check if interior perimeter drain tile systems are open to air or sealed off.
- Exterior drain tile termination: Inspect where outdoor foundation drains terminate to ensure radon is not pulling back through them.
5. Indoor Air Dynamics & HVAC Interaction
- Air handler pressure effects: Measure radon levels while the central heating and cooling fan is actively cycling.
- Return ductwork leakage: Inspect negative-pressure return ducts in unconditioned spaces (like crawl spaces) for leaks.
- Supply ductwork leakage: Check for positive-pressure supply duct leaks that could drive building depressurization.
- Combustion appliance backdrafting: Conduct a worst-case draft test on natural draft water heaters or furnaces.
- Exhaust fan depressurization: Measure the pressure drop caused by kitchen hoods, clothes dryers, and bathroom fans.
- ERV/HRV balance: Check the airflow balance of Energy Recovery Ventilators to avoid negative indoor pressure.
- Outdoor air intake positioning: Ensure HVAC fresh air intakes are located away from the radon vent exhaust stack.
- Whole-house fan evaluation: Evaluate the depressurization risk when large ceiling-mounted exhaust fans are running.
6. Environmental Conditions & QA Testing
- Barometric pressure trends: Track local weather patterns and barometric pressure drops during diagnostic testing phases. This is best done with long term continuous radon monitoring.
- Soil moisture saturation: Assess whether rain or high water tables are blocking sub-slab air communication pathways.
- Wind load effect: Check if high winds are altering building pressure fields or creating a stack effect.
- Short-term charcoal tracking: Deploy 48-hour charcoal canisters to verify rapid system drawdown efficiency.
- Continuous Radon Monitor (CRM): Run a calibrated CRM to monitor hourly spikes and verify overall system stability.
- Multiple simultaneously radon tests, performed in different rooms and different levels of the home at the same time if possible, will often yield the most helpful test data.
To troubleshoot a specific radon system that is not performing as it should, we will need to determine critical building and radon system information such as:
- Radon Quote
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