Can Radon Mitigation Systems Fail? Signs to Watch For in Radon Mitigation System Failures

A radon mitigation system installed by a qualified professional and verified through post-installation testing is a reliable piece of home infrastructure. But reliable does not mean infallible, and no mechanical system runs indefinitely without the possibility of a problem developing. Understanding how mitigation systems can fail — and what signs indicate something is wrong — is the practical complement to the maintenance knowledge covered in our post on routine system maintenance. Where that post addressed what normal, ongoing care looks like, this post addresses what abnormal looks like and what to do when you see it.

The distinction between maintenance and failure is worth drawing clearly at the outset. Maintenance is what you do to keep a properly functioning system performing well. Failure is what happens when the system stops performing as designed — when the protection it was installed to provide is no longer being delivered at the level the post-installation test confirmed. Both topics matter, and they are different enough to warrant separate treatment.

What System Failure Actually Means

Radon mitigation system failure does not always mean a dramatic mechanical breakdown. It does not necessarily mean the fan has stopped running entirely or the pipe has physically come apart. In many cases, system failure is gradual and partial — a decline in performance that allows radon levels to rise above the post-installation baseline without any obvious visible sign that something has changed.

This is why the two-year retest discussed in our post on how often to test is so important. A system can appear to be operating normally — fan running, manometer showing some displacement — while actually underperforming relative to what it was doing at installation. The radon level in the home may have climbed from the post-installation result of 0.8 pCi/L to 3.5 pCi/L without any dramatic event signaling that change. Only a current radon test reveals this kind of gradual performance degradation.

True system failure — the kind that produces no protection at all — is typically more visible. But partial performance degradation is the more common scenario, and it is the one most likely to go unnoticed without periodic testing.

The Manometer: First Line of Detection

The manometer is the system's built-in performance indicator, and changes in manometer readings are the most immediate signal that something may be wrong. As we established in our posts on system mechanics and routine maintenance, the colored liquid in the manometer should be visibly displaced to one side when the system is operating correctly. A level manometer — liquid sitting evenly in both arms of the U-tube — is the clearest possible signal that the system is not creating suction.

A level manometer can result from several different causes, and identifying which one applies to your system determines the appropriate response.

The fan may have stopped running. This is the most straightforward cause — the motor has failed, a power interruption has not been restored, or a tripped circuit breaker has cut power to the fan without the homeowner's awareness. Before concluding the fan has failed mechanically, verify that it is receiving power. Check the circuit breaker serving the fan circuit. Listen for the fan's characteristic hum — its absence when power is confirmed is a clear indication of motor failure.

A pipe obstruction or disconnection may be preventing suction from reaching the suction point beneath the slab. A bird's nest in the discharge cap, a section of pipe that has separated at a joint, or physical damage to the pipe anywhere along its run can all interrupt the suction pathway without affecting the fan's operation. A fan running against a blocked or disconnected pipe will not create meaningful suction at the sub-slab level, and the manometer will reflect this.

The suction point itself may have become ineffective. Over time, the sub-slab conditions beneath the suction point can change in ways that reduce the system's ability to create an effective pressure field. Settlement can shift the aggregate layer. Moisture infiltration can alter sub-slab communication. In some cases, the pit created at the suction point during installation can become partially obstructed. None of these are common occurrences, but they are possibilities worth being aware of.

Fan Performance Degradation

Fan failure at the extreme end — complete motor seizure — is detectable immediately through a level manometer and the absence of the fan's operating sound. But fans rarely fail catastrophically and instantly. More commonly they degrade gradually over their service life, delivering less suction over time as the motor ages, bearings wear, and efficiency declines.

A fan in the early stages of performance degradation may continue to displace the manometer liquid — indicating it is running — while producing insufficient suction to maintain the pressure field that was present at installation. The manometer shows the system is operating, but the radon test shows it is not operating at the level it was when installed.

Signs that a fan may be approaching the end of its effective service life include a change in its operating sound — a new hum, vibration, or intermittent noise that was not present previously. Reduced manometer displacement compared to what it showed when the system was new — if you have any memory or record of what the initial displacement looked like — is another indicator. And most definitively, a two-year retest that shows radon levels have risen significantly from the post-installation baseline points directly to a fan performance issue as one of the likely causes.

Fan replacement is straightforward and does not require reinstalling the pipe system. A qualified mitigation professional can assess the fan's performance, confirm that replacement is the appropriate response, and install a replacement fan that restores the system to its original performance level. As we discussed in our post on system maintenance, this is a targeted component replacement rather than a whole-system reinstallation.

New Radon Entry Points

A system that is mechanically functioning perfectly can still produce elevated radon levels if new entry points have developed that the system's pressure field does not adequately address. Michigan foundations continue to age and develop new cracks, gaps, and penetrations over time — freeze-thaw cycling, settling, and normal material aging all contribute. A new crack in the basement floor or wall can create an entry pathway that bypasses the sub-slab pressure field the system maintains.

This type of failure is particularly challenging to detect through visual inspection alone because the system appears to be working correctly — fan running, manometer displaced — while a new entry point is allowing radon to circumvent the protection the system provides. Again, the two-year retest is the mechanism that catches this. A rising radon level with a normally functioning system points toward new entry points or changes in sub-slab conditions as likely causes.

The response may involve sealing the identified new entry points, adding a suction point to extend pressure field coverage, or adjusting fan capacity if sub-slab conditions have changed in ways that reduce the existing system's effectiveness. A qualified mitigation professional can assess the specific situation and recommend the appropriate correction.

Discharge Cap Damage

The discharge cap at the top of the pipe above the roofline is a component that Michigan homeowners rarely think about — it is out of sight and out of mind. But a damaged or missing discharge cap can affect system performance in ways that range from minor to significant depending on the nature of the damage.

A discharge cap serves several functions: it prevents precipitation from entering the pipe, keeps birds and insects from nesting in the open pipe end, and directs the discharged radon-laden air away from the building in a pattern that prevents re-entry through nearby windows or HVAC intakes. A cap that has been damaged by ice, wind, or physical impact — not uncommon given Michigan's winters — may allow water infiltration that increases the moisture load on the fan, may allow nesting that partially obstructs the discharge, or may alter the discharge direction in ways that affect performance.

Checking the discharge cap is not something most homeowners can easily do from the ground, but it is worth asking a roofing contractor or mitigation professional to inspect periodically — perhaps at the same interval as the two-year radon retest. Any damage or blockage observed during inspection should be addressed promptly.

What to Do When You Suspect a Problem

The appropriate response to any of the failure signs described in this post is contact with a qualified mitigation professional — the company that installed your system if they are still operating and reachable, or another certified radon mitigation professional if not. Do not attempt to diagnose or repair a failing mitigation system without professional assessment. The stakes — your family's radon exposure during the period the system is underperforming — are significant enough to warrant prompt professional attention rather than extended DIY investigation.

Bring whatever information you have to that conversation: your post-installation test result, any recent retest results, your observations about the manometer and fan sound, and any physical changes to the home — renovations, foundation repairs, flooding — that might be relevant. The more context a professional has, the more efficiently they can identify the cause of the problem and recommend the appropriate correction.

The Reassuring Reality

System failures of the magnitude that eliminate all radon protection are uncommon in properly installed systems. The more typical scenario is gradual performance change over years that is caught and corrected through regular retesting and attentive monitoring. A homeowner who checks the manometer monthly, conducts the two-year retest consistently, and pays attention to changes in the fan's operating sound is doing everything needed to catch problems early and address them before they become significant.

The system is working for you every hour of every day. The small investment of attention that monitoring requires is a reasonable return on what the system provides.

At All Michigan Mitigation, we assess and service mitigation systems installed by our own team and by other contractors, and we bring the diagnostic expertise to distinguish between maintenance needs and genuine system failures efficiently. Radon is everything we do, and that includes being the resource our clients call when something about their system needs a closer look.

Visit us at allmichiganmitigation.com to schedule a system assessment or retest, or to reach out with any concerns about your mitigation system's performance.

All Michigan Mitigation is a West Michigan radon testing and mitigation company dedicated exclusively to helping homeowners understand and eliminate radon risk in their homes.