Start with the manometer
The U-tube gauge on the pipe answers the first question in five seconds. If the two liquid columns are level, there is no suction — the fan has failed, or the pipe is blocked or disconnected. If the columns show a clear offset, the fan is moving air and the problem, if any, lies in the design.
The decision matrix
| Symptom | Likely cause | Right fix |
|---|---|---|
| No manometer offset, fan silent | Failed fan motor | Fan replacement |
| Fan grinding or rattling | Worn bearings | Fan replacement |
| Good offset, radon still above 4.0 | Insufficient pressure field | Add suction point(s) |
| Good offset, radon crept up over years | Reopened cracks or new penetrations | Re-seal and retest |
| Fan mounted in a basement or closet | Improper installation | Relocate — system rework |
| Exhaust ends below the roofline | Improper termination | Re-route the upper pipe run |
| Cracked, chalky exterior PVC | UV degradation | Replace the affected run |
When fan replacement is the answer
- The original system brought the home under 4.0 pCi/L and documentation proves it.
- The pipe run, termination, and fan location all meet protocol.
- The fan is simply at the end of its service life, typically 8–12 years.
- Replacement is a 1–2 hour visit, followed by a verification test.
When you need more than a fan
- The home has never tested below the action level, even with the fan running well.
- There is only one suction point in a home over tight, poorly communicating soil.
- A significant addition was built after the system was installed.
- The fan sits inside conditioned space, which cannot be corrected by swapping the unit.
- A basement was finished, changing airflow and covering sealed areas.
Cost comparison
| Scope | Relative cost | Downtime |
|---|---|---|
| Fan replacement only | Lowest | 1–2 hours |
| Fan plus re-sealing | Low | Half day |
| Adding a suction point to an existing system | Moderate | Half to full day |
| Full system replacement or re-route | Highest | 1–2 days |
Related services
Keep learning
- What Radon Mitigation Costs — and What Drives the PriceRadon mitigation is priced on how hard it is to move air under your specific foundation — not on square footage. Here is what each line item actually represents.
- How Radon Mitigation Actually WorksA mitigation system does not filter radon. It reverses the pressure difference that pulls soil gas into your home in the first place.