How to Check If Your Radon Mitigation System Is Working

Check #1: The Manometer (Daily/Weekly)

The manometer is a U-shaped tube filled with red or blue liquid, mounted on your radon pipe. It's your primary system status indicator.

How to read it:

• System working: The liquid in one side of the U is lower than the other. The fan is creating negative pressure, pulling the liquid toward the suction side.
• Fan failed: Both columns are at equal levels. No pressure differential = no suction = no radon removal.

The manometer doesn't tell you how much radon is in the air — it tells you whether the fan is creating the pressure that makes the system work. It's a necessary but not sufficient check.

What if the differential looks smaller than usual?

A noticeably reduced differential (both columns closer together than they used to be) can indicate:

• Fan performance degradation (motor wearing out)
• A new air leak in the pipe that's reducing system pressure
• A change in sub-slab conditions

Run a radon test if you notice the differential decreasing over time.

Check #2: The 30-Day Post-Mitigation Test

This is the first real confirmation that the system is reducing radon, not just running. After installation, place a short-term charcoal test kit in the same location as the original test (basement, lowest livable level) and let it run for 48–96 hours under closed-house conditions.

What you're looking for:

• Result below 4.0 pCi/L: System is working; EPA action level is being met
• Result below 2.0 pCi/L: System is working well; typical result for a properly installed system
• Result above 4.0 pCi/L: The system is not achieving adequate reduction — contact your contractor

Most properly installed systems achieve post-mitigation levels of 0.5–2.0 pCi/L, even in homes that started at 8–15 pCi/L.

Check #3: The Biennial Retest

Every 2 years, run a long-term alpha track test (90 days) in the same location. This is the most important ongoing maintenance check because:

1. It catches fan degradation before failure: A slowly declining fan shows up as slowly rising radon before the manometer goes flat
2. It catches new entry points: Foundation settling, renovation, or plumbing work can open new radon pathways
3. It provides documentation: For real estate, insurance, or simply your own records

Keep a log: original pre-mitigation level, post-mitigation level, and each subsequent biennial test result with dates. This history is valuable if you ever sell.

What to Do If Levels Have Risen

If a retest shows radon levels significantly above your original post-mitigation baseline:

1. Check the manometer first — confirm the fan is actually running
2. Listen for unusual fan sounds — grinding or rattling indicates bearing wear
3. Check for new foundation penetrations — any renovation work that cut into the slab or walls
4. Call your contractor — if the fan is running and nothing obvious has changed, the system may need an additional suction point or a higher-capacity fan

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