The previous owner already had a system put in. Why is my house still over 4 pCi/L?

Cause 1: The fan aged out

Inline radon fan bearings last about 8 to 12 years in continuous operation. Past that point, the fan does not usually fail outright. It loses suction gradually. The manometer gauge on the pipe in the basement is the early warning. If the two fluid columns are closer together than they used to be, the fan is moving less air.

We see this pattern a lot in Rochester homes where the system was installed in the early 2010s and the homeowner has been watching the gauge but not testing. The gauge still reads non-zero, just lower than it did at install. The basement, meanwhile, has been creeping back up.

The fix is a fan swap. New fan, new manometer if the old one is cloudy, post-install test to confirm. Half a day of work.

Cause 2: The original install was a poor fit

A mitigation system works by depressurizing the air space under the slab. The fan pulls on a pipe that connects to that air space through one or more suction points. The suction has to be strong enough to overcome the natural pressure that pulls soil gas up into the home.

Common original-install issues:

• One suction point where the slab really needed two or three. Common in homes with multiple slab pours or additions.
• Thin or missing gravel under the slab. The fan has nothing to pull through.
• An undersized fan for the home or the foundation.
• Poor sealing at the slab penetrations, the cold joint, or the sump pit cover.

A diagnostic visit walks through these by measuring suction at different points and looking at what the original installer left behind. Adding a second suction point is a common fix. Upsizing the fan is another. We have done both on plenty of older Rochester systems.

Cause 3: The home has changed

Any work that changes the slab or the foundation envelope can shift the radon picture. The most common culprits we find:

• A basement renovation that opened a slab penetration and was sealed back imperfectly.
• A new sump pit, or a sump pit cover that has cracked or been removed.
• A new HVAC system that changed the home's pressure balance.
• An exterior project that disturbed the soil near the foundation.
• A new addition built over part of the old footprint.

These changes are not all visible from the basement. Sometimes the homeowner remembers the project, sometimes they do not. The diagnostic visit catches what the gauge cannot.

What a diagnostic visit looks like

1. A short-term test (we usually leave a continuous monitor for 48 hours) to confirm the current number.
2. A walk-through of the existing system. Fan condition, pipe routing, slab penetrations, sump pit covers, cold joints.
3. Suction measurements at the existing suction point and at any candidate new locations.
4. A conversation about what we found and what the realistic options are. Usually a fan swap, an added suction point, a better seal at a specific penetration, or some combination of the three.

What changes the answer

• Age of the existing system. Anything past 10 years should expect a fan swap regardless of the other findings.
• Slab and foundation type. A walkout, a finished basement, or a home with multiple additions each ask their own questions.
• Recent home changes. The conversation gets a lot shorter if the homeowner can point to a specific project.
• Sump pit involvement. A sump cover that has degraded is the single most common quiet failure point.