Why Many Radon Mitigation Systems Fail (And How We Fix Them)

Why Many Radon Mitigation Systems Fail (And How We Fix Them)

Radon mitigation systems are supposed to be simple: install a fan, depressurize the slab, and watch the radon levels drop. But in reality, many systems installed in Calgary homes fail to reduce radon to safe levels — and homeowners are left confused, frustrated, and unsure of what went wrong.

The truth is that radon mitigation is not a “one‑size‑fits‑all” process. It’s building science. It’s diagnostics. It’s pressure management. And when companies skip those steps, the system fails. At Spectra Radon, we’re called in regularly to fix systems installed by other companies — and the patterns we see are remarkably consistent.

This article explains why radon mitigation systems fail, how to recognize the warning signs, and what it takes to fix them properly.

The Most Common Reason Radon Systems Fail: No Vacuum Under the Slab

When we’re called to a home where a mitigation system is running but radon levels remain high, the very first thing we check is whether the system is actually pulling vacuum under the slab. This is the foundation of every successful mitigation system. If the fan isn’t creating negative pressure beneath the concrete, the system simply cannot work.

You’d be surprised how often we find systems where the fan is spinning, the pipe is humming, the manometer shows a pressure difference — and yet there is no measurable vacuum under critical areas of the slab at all. In these cases, the system is nothing more than a noisy decoration. It looks like a radon system, it might sound like a radon mitigation system, but it isn’t doing anything.

The most common cause? The fan has failed or seized.  

Fans installed by high‑volume companies are often cheap, undersized, or installed incorrectly, leading to premature failure. But even when the fan is working, many systems still fail because the installer never performed pressure field extension (PFE) testing — the diagnostic step that confirms whether the suction point is actually communicating with the entire slab.

Skipping PFE is like installing a furnace without checking whether the ducts are connected.

What Happens When Installers Skip Diagnostics

When a mitigation system is installed without diagnostics, the symptoms are predictable. We see the same patterns again and again:

Radon levels barely change after installation.   This is the clearest sign that the suction point is in the wrong location or the system isn’t depressurizing the slab.

The system uses the wrong materials.   SDR‑35 sewer pipe is a common shortcut. It’s thin, leaks at the joints, resonates noise, and is not designed for radon mitigation. Proper Schedule 40 piping is the industry standard — but companies focused on speed and cost savings often ignore this.

The suction point is placed in a “dead zone.”   Installers who don’t understand soil permeability often choose the easiest drilling location, not the correct one. If the suction point is drilled into compacted fill, structural slab sections, or isolated slab compartments, the system will never work.

Slab penetrations are left unsealed.   Cold joints, sump lids, plumbing penetrations, mechanical room gaps, and cleanout covers are often ignored. Without sealing, the system loses vacuum and pulls air from the wrong places.

The fan is the wrong size.   Undersized fans can’t move enough air. Oversized fans short‑circuit the system. Both are signs of installers who don’t understand pressure dynamics.

The installer is uncertified — or claims to be.   We are seeing more and more systems installed by people with no radon training at all. Some even claim certification they don’t have. These are the systems that fail most dramatically. Always check to make sure your installer is certified.

The Rise of “Marketing‑First” Radon Companies

One of the most troubling patterns we see is the rise of companies that focus more on marketing than on building science. These are the companies with flashy TikTok videos, daily social media posts, and aggressive advertising — but very little to no technical expertise behind the scenes.

They install systems quickly, cheaply, and in high volume. They skip diagnostics because diagnostics take time. They hire installers with no science background because it keeps costs down. And they rely on the fact that most homeowners don’t know what a proper mitigation system looks like.

These are the systems we are called to fix most often.

A radon system is not a cosmetic product. It’s a pressure‑management system that protects your family’s health. It requires knowledge, not marketing.

Common Failure Patterns We See in Calgary Homes

After regularly fixing failed systems, we’ve identified several recurring patterns:

1. Wrong fan installed   This is the number one failure. Fans are chosen based on soil conditions, slab thickness, permeability, and PFE results — not guesswork. When companies skip diagnostics, they almost always choose the wrong fan.

2. No sealing of radon entry points   Unsealed cold joints, sump lids, slab penetrations, and mechanical room gaps allow air to bypass the system entirely.

3. Suction point drilled in the wrong location   Installers often choose the easiest drilling spot, not the one that actually communicates with the slab.

4. SDR‑35 sewer pipe used instead of proper radon pipe   This is a cost‑cutting shortcut that compromises system performance and longevity.

5. No PFE testing performed   Without PFE testing, the installer has no idea whether the system is depressurizing the slab. It’s guesswork — and it fails.

6. Systems installed by uncertified or falsely “certified” installers   This is becoming more common, and the results speak for themselves.

How We Fix Failed Radon Mitigation Systems

When we’re called to repair a failed system, we follow a structured, diagnostic‑first process. We don’t guess. We measure. We test. We verify. And we fix the root cause — not just the symptoms.

Step 1: Replace the wrong fan   Most failed systems start with the wrong fan. We replace it with the correct model based on actual diagnostics and soil conditions.

Step 2: Complete the sealing the original installer skipped   We seal every radon entry point properly — cold joints, sump lids, penetrations, mechanical room gaps, and more. Sealing is not optional. It’s part of the pressure system.

Step 3: Perform proper PFE testing   We measure pressure field extension across the slab to confirm that the system is actually depressurizing the entire footprint of the home.

Step 4: Relocate or enlarge the suction point if needed   If the suction point is in a dead zone, we move it. If the suction pit is too small, we enlarge it. If the slab is compartmentalized, we add additional suction points.

Step 5: Replace improper materials   If the system was built with SDR‑35 or other incorrect materials, we remove it and rebuild it properly.

Step 6: Rebuild the system from scratch when necessary   In some cases, the original system is so poorly designed that the only solution is to remove it entirely and start over. We do this when it’s the only way to guarantee performance.

Final Thoughts

Radon mitigation systems fail for predictable reasons — and almost all of them come down to skipped diagnostics, poor training, and cost‑cutting shortcuts. A radon system is not just a pipe and a fan. It’s a pressure‑management system that requires building‑science knowledge, proper materials, and careful testing.

At Spectra Radon, we fix failed systems because we understand the science behind them. We diagnose before we install. We measure before we drill. And we verify before we leave.

If your radon levels are still high after installing a mitigation system, or if you’re unsure whether your system was installed correctly, we can help you find the real cause — and fix it properly.