Radon Connect
What happens next

What happens after replacing a fan

“The fan was replaced. Do I need to test again, and what am I supposed to check?”

A fan replacement is a small job with one important consequence: your baseline is now wrong. The gauge reading you have been comparing against belongs to the old fan, and a new one — even the same model — will typically sit somewhere slightly different.

The sequence is short. It exists mostly because the previous failure probably went unnoticed for a while, and this is the moment to make sure that cannot repeat.

  1. The same day

    Record the new baseline before the technician leaves

    Read the gauge with the new fan running and write the number down with the date. Ask what reading would indicate a problem. If the old fan failed gradually rather than suddenly, ask what they saw when they took it off — a blocked pipe or a failed seal produces a different story from a worn motor, and it changes what you watch for.

    Whose move
    You, while the technician is still there to answer.
    If this does not happen
    Without a new baseline you are comparing future readings against a number that no longer applies, which is worse than having no baseline at all.
    Where people fall out
    Assuming the reading should match the old one. Fans vary, installations settle, and a different number is not a fault.

  2. 24 hours to about 30 days

    Retest, especially if the failure went unnoticed

    If the old fan had been failing for an unknown period, the house was unmitigated for that period and you have no measurement covering it. A test now under closed conditions confirms the new fan is doing the job and gives you a current figure. If the replacement was preventative and the gauge never dropped, the case for an immediate retest is weaker.

    Whose move
    You. A replacement visit rarely includes a measurement unless you ask.
    If this does not happen
    You return to assuming the system works, which is the state that allowed the last failure to go unnoticed.
    Where people fall out
    Skipping the retest because the fan is visibly new. Visible newness is not a measurement, and the pipe and seals were not replaced.

  3. Within a week

    File the new warranty and update the record

    A replacement fan carries its own warranty with its own start date, which is now different from the rest of the system. Note the model, the date, the installer, and the terms. Update the house file rather than adding a second uncoordinated document to it.

    Whose move
    You, once, while the model number is still in front of you.
    If this does not happen
    When the next failure comes, warranty status turns on a date nobody recorded, and the default assumption is out of warranty.
    Where people fall out
    Filing the receipt without the model number. The model determines the replacement match and sometimes the warranty term.

  4. Set it now, for a year out

    Make a second silent failure impossible

    The reason a fan failure goes unnoticed is that nothing announces it. A calendar reminder for an annual check is the entire fix, and it takes less time to set than to think about. Some homeowners add an audible or visual failure alarm at this point, which is a reasonable response to having just lived through the alternative.

    Whose move
    You, in the two minutes after reading this.
    If this does not happen
    The conditions that produced the last undetected failure remain exactly as they were.

  5. Every year, then every two

    Back to the ordinary routine

    From here the maintenance sequence is the same as for any system: an annual ten-minute check against your new baseline, and a measurement every couple of years or after work that changes airflow.

    Whose move
    You, on the reminder you just set.
    If this does not happen
    The routine lapses and the system reverts to an assumption over the following few years.

When it goes differently

A sequence with only one ending is a script rather than a description. These are the divergences worth knowing about before you are in one.

The old fan had clearly failed and you do not know for how long
Retest. The house was unmitigated for an unknown period and no existing measurement covers it.
The replacement was preventative and the gauge never dropped
A retest is optional rather than indicated. Record the new baseline and continue the ordinary cadence.
The new fan is noisier than the old one
Noise has identifiable causes, some of which are mounting rather than the fan. It is worth raising while the visit is recent.
The retest after replacement came back elevated
The fan was not the only problem. This is the failed-system diagnosis path, not a fan question.

Related

Confidence and limits of this page

Every decision resource on this platform states its own boundaries. This is not a disclaimer — it is the part of this sequence you should read before relying on it.

What we knowClaims on this page we stand behind, each traceable to an approved source or to observable structure.
  • A pressure gauge reading is specific to an installation and its fan, so replacing the fan changes the reference reading.
  • Published guidance recommends retesting after significant changes to a mitigation system.
  • Mitigation fans are continuously running components with finite service life, so replacement is an expected event.
What we do not knowQuestions you may reasonably have that this page does not answer.
  • How long the previous fan had been underperforming, unless a gauge reading or a measurement happens to bracket it.
  • How long the replacement will last, which depends on model and conditions.
What research would settle itWhat it would actually take to answer the above — naming it is the difference between honesty and hedging.
  • Field failure data by fan model and installation age, which would replace a general expectation with a distribution.
  • Gauge readings paired with measurements over time, which would let anyone interpret a gauge change quantitatively.
What we do not claimClaims you might expect to find here and will not, with the reason.
  • We do not claim a service life for any named fan model, because we hold no field failure observations.
  • We do not recommend any fan, alarm product, or service plan.
  • We do not claim a specific gauge reading is correct for your system, because it depends on the installation.
What we cannot independently verifyFacts this page relies on that we could not confirm ourselves.
  • What condition the removed fan was in, unless the technician documented it.
  • Manufacturer warranty terms for your specific unit, which are set by the manufacturer and the installer.

Sources

  1. U.S. EPA — Consumer’s Guide to Radon Reduction

Get quotes from credentialed local contractors

Free to request and no obligation. We verify credentials with the issuing authority before any request routes to a contractor.

Start a request