Key Considerations for Professional Radon Fan Installation
When I first started working in radon mitigation around Jefferson County, I quickly learned that a mitigation system is only as good as its weakest component. You can have the best in-line fan on the market, but if the radon fan installation is sloppy or the PVC pipe runs are poorly sealed, the whole reduction system underperforms. Over the years, I have seen homeowners in Arnold and Festus spend good money on equipment only to get disappointing post-mitigation test results because the fan was mounted in a way that reduced its lifespan or allowed condensation to pool.
That is why I want to share some practical insights about getting a radon fan installation right. Whether you are a contractor, a homeowner in High Ridge or Hillsboro, or just someone researching active soil depressurization, understanding the details of how a radon fan is installed can save you headaches and keep your indoor radon levels low.
Why Fan Placement Matters
A radon mitigation system typically works by creating negative pressure under the slab or under a sealed crawl space. A fan pulls radon-laden soil gas from beneath the home and vents it above the roofline. The most common approach is sub-slab depressurization, which relies on a well-placed suction pit and a continuous column of PVC pipe. The radon fan is the heart of that system.
If the fan is installed outdoors, it should be mounted close to the house but in a location where rain and snow cannot directly hit the housing. I have seen fans mounted flush against a wall with no drip loop, and within a year the motor housing filled with water. That is an expensive lesson. A proper radon fan installation includes a condensate bypass or a p-trap arrangement at the lowest point of the pipe run so that moisture drains away from the fan. Without that, water can collect in the fan housing and cause the motor to fail prematurely.
Choosing Between RadonAway and Fantech
Two brands dominate the residential radon market: RadonAway and Fantech. Both make reliable in-line fans designed specifically for active soil depressurization. The choice often comes down to the specific static pressure requirements of the job. A RadonAway fan, for example, might be better suited for a home with a tight clay soil and a deep suction pit, while a Fantech fan can handle higher airflow for larger crawl spaces.
No matter which brand you choose, the radon fan installation must follow the manufacturer's mounting orientation. Some fans need to be mounted vertically; others can sit horizontally. Ignoring those specs can lead to premature bearing wear and noise complaints. I always carry a copy of the manual on site and double-check the orientation before drilling any holes.
Piping and Sealing Details
The pipe run from the suction pit to the fan and then up to the exhaust point should be smooth-wall PVC pipe, usually 3-inch or 4-inch diameter. Every joint should be glued with a quality PVC cement and primed for a gas-tight seal. A leak on the suction side of the fan will pull in indoor air instead of soil gas, reducing the effectiveness of the whole system. On the discharge side, a leak can allow radon to vent into a crawl space or attic instead of outside.
One detail that is often overlooked is the need for a manometer or a U-tube manometer somewhere visible on the system. This simple device shows the pressure difference the fan is creating. A reading that drops suddenly can indicate a blockage, a fan failure, or a leak. I tell homeowners in Jefferson County to check their manometer monthly and write down the reading. If it changes, call a professional. A properly installed manometer is a cheap insurance policy.
Condensation and Cold Climate Considerations
Missouri winters can be damp and cold. When warm, moist soil gas travels up through a cold PVC pipe, condensation forms inside. If the pipe runs horizontally for any distance, water can collect and eventually block the pipe. That is why a good radon fan installation includes a condensate bypass or a p-trap at the low point of the pipe run. The bypass allows water to drain out through a small hole or a tee fitting with a check valve, so it does not reach the fan.
I have seen systems in Arnold and Festus where the installer skipped the bypass to save time. Within one winter, the fan was humming but moving almost no air because the pipe was half full of water. The homeowner thought the fan was running fine because they could hear it. Always include a condensate bypass, even if the pipe run is short.
Testing and Verification
After any radon fan installation, the system should be tested. A short-term radon test, usually 48 hours to 90 days, will tell you whether the active soil depressurization is working. I recommend waiting at least 24 hours after installation before starting the test, to let the system stabilize. If the test shows levels above 4 picocuries per liter, something is wrong with the installation or the home has additional entry routes that were not sealed.
Air Sense Environmental, which serves Jefferson County homes in Arnold, Festus, High Ridge, and Hillsboro, follows a thorough commissioning process. They check the manometer reading, listen for unusual fan noise, and verify that the exhaust point is above the roofline and away from windows. They also inspect the sealed crawl space or sub-slab sealant for any gaps. A professional installer will leave a label on the fan with the date of installation and the expected manometer reading range.
Common Mistakes to Avoid
Over the years, I have come across a few recurring issues that can undermine an otherwise solid radon fan installation:
- Mounting the fan directly on the pipe without vibration isolation. The fan motor creates vibration that can loosen joints over time. Use a short section of rubber coupling or a vibration isolator between the fan and the pipe.
- Using the wrong size pipe. A 3-inch pipe is standard for most homes, but a very long run or a high static pressure situation may call for 4-inch. Undersizing the pipe starves the fan.
- Forgetting to seal the suction pit. The pit itself is just a hole dug under the slab. The dirt around the pit should be sealed with a concrete patch or a plastic boot to prevent air from short-circuiting.
- Placing the fan too close to an openable window or a neighbor's property line. The exhaust plume carries radon, and you do not want it re-entering the home or bothering a neighbor.
- Skipping the post-installation test. A system that looks perfect may still not be pulling enough vacuum. Always test.
When to Call a Professional
Active soil depressurization is not a weekend DIY project for most homeowners. The electrical work, the structural considerations for drilling through a slab, and the need for an airtight seal all require experience. A homeowner in Hillsboro might be tempted to buy a fan online and install it themselves, but a poorly executed radon fan installation can actually increase radon levels by creating new pathways for soil gas to enter the home. Professional installers like those at Air Sense Environmental carry liability insurance and know the local soil conditions in Jefferson County. They also have the proper tools to measure static pressure and airflow.
If you are in Arnold, Festus, High Ridge, or Hillsboro and suspect you have a radon problem, start with a test. If the test comes back high, find a qualified mitigator who can walk you through the system design and the expected radon fan installation process. A good mitigator will explain every step, show you where the fan will go, and tell you how to maintain the system. They will also leave you with a manometer reading so you can monitor performance yourself.
Radon mitigation is not complicated, but it requires attention to detail. A well-designed and properly executed radon fan installation will protect your family for decades with very little maintenance. That is a worthwhile investment for any home in Jefferson County.