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True Trade Path

Diagnostic guide

Radon Test Came Back High

Elevated radon needs mitigation — sealing alone rarely fixes; active depressurization is standard.

System
Safety
Causes covered
5
You can check
1 without a technician

Stop and read this first

  • Radon is long-term lung risk.
  • Retest after mitigation.
  • Use certified mitigator.

Work through these in order

Ordered from most to least likely. Working top down means you rule out the cheap, common causes before paying anyone to look at the expensive, rare ones.

  1. Soil gas entry through slab cracks

    CommonNeeds a pro
    How to check
    High long-term test.
    The fix
    Install sub-slab mitigation fan.

  2. Stack effect pulling gas indoors

    CommonNeeds a pro
    How to check
    Higher in winter.
    The fix
    Mitigation plus air sealing.

  3. Well water radon (rare)

    PossibleNeeds a pro
    How to check
    High water test.
    The fix
    Aeration or GAC treatment.

  4. Test placement error

    PossibleYou can check
    How to check
    Test in humid crawl.
    The fix
    Retest per EPA protocol.

  5. No mitigation after remodel

    PossibleNeeds a pro
    How to check
    New addition higher reading.
    The fix
    Extend mitigation to new slab.

Direct answer

Elevated radon needs mitigation — sealing alone rarely fixes; active depressurization is standard. Start with the safest homeowner checks in the causes list, then call a licensed hvac technician if resets, cleaning, or simple replacements do not resolve it, or if you see heat, sparking, gas odor, or spreading water.

Severity and urgency

Fix within days

Comfort and equipment damage escalate if the symptom runs for weeks without diagnosis.

Cost of ignoring it

Delaying radon test came back high often turns a $150–$400 diagnostic visit into hundreds or thousands in water damage, mold remediation, fire damage, or premature equipment replacement. Document when symptoms started for insurance and warranty conversations.

How a pro will diagnose it

Expect a written diagnosis: what was tested, what failed, and options ranked by cost and life expectancy. For hvac technician work, verify license, insurance, and permit requirements before authorizing repairs.

Prevention and maintenance

  • Keep maintenance logs — filter changes, annual tune-ups, gutter cleaning, and test button checks on GFCI and smoke/CO alarms.
  • Fix small leaks, stains, and nuisance trips when they start; they rarely self-resolve.
  • Match parts and breakers to listed ratings; avoid oversized breakers on undersized wire.
  • Improve ventilation and drainage before cosmetic cover-ups.
  • Use qualified pros for gas, refrigerant, and structural connections.

For trade owners

Pricing this job as a contractor?

Homeowners see national ranges on this page. If you are building the estimate, use the same scope assumptions — then price to burdened labor, overhead recovery and a real margin.

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Find a licensed pro

When you are ready to hire for radon test came back high, start with licence verification — not with whoever answered first.

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Rankings are never sold. Order reflects verification depth and relevance, not payment.
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Verify any licence yourself before signing: state licensing hub.

Common questions

Could soil gas entry through slab cracks be causing this?
High long-term test. Install sub-slab mitigation fan.
Could stack effect pulling gas indoors be causing this?
Higher in winter. Mitigation plus air sealing.
Could well water radon (rare) be causing this?
High water test. Aeration or GAC treatment.
Could test placement error be causing this?
Test in humid crawl. Retest per EPA protocol.
What is the most common cause of radon test came back high?
Usually the first "common" cause in the guide — often maintenance, a tripped safety device, or a failed single component. Confirm with the checks listed before assuming worst-case failure.
Is radon test came back high dangerous?
It can become dangerous if ignored — moisture, heat, and electrical faults escalate over time.
Can I fix this myself?
DIY is appropriate only for causes marked diy in the guide, with power/gas/water shut off. Sealed systems, gas lines, roofs, and panels are pro work.
How much does repair typically cost?
Simple fixes run $0–$200 in parts; single-component repairs often $150–$500 installed; major system or structural work can be $1,000–$10,000+. Get three written quotes for big jobs.
How soon should I act?
Fix within days: Comfort and equipment damage escalate if the symptom runs for weeks without diagnosis.
Will resetting a breaker or GFCI fix it?
Reset once after correcting the obvious cause. If it trips again immediately, stop — repeated trips signal a fault that needs tracing.
Does homeowners insurance cover this?
Sudden and accidental damage (storm, fire, burst pipe) may be covered; gradual wear, maintenance, and code upgrades usually are not. Document with photos and dates.
What should I check first?
Start with the top two common causes in the guide — power, water shutoffs, filters, batteries, and tripped safety devices — before opening equipment enclosures.
Why did this start suddenly?
Sudden onset often tracks to a failed part, storm event, pest damage, or a recent change (new appliance, remodel, freeze). Gradual onset suggests wear or slow leaks.
Repair or replace?
If repair exceeds 50% of replacement cost on equipment past half its expected life, or the unit is out of warranty with a major sealed-system failure, replacement usually wins.

Once you know what it is

Step one

Know what it should cost

Get the range before you call, so the first number you hear is not the only number you have.

Step two

Decide repair or replace

On equipment near end of life, the repair is usually the first of several.

Step three

Check the quote

Compare against the typical range and confirm the terms before you sign.

Radon Mitigation cost guideRepair or replace calculatorEstimate repair costAnalyze a quote

What the fix costs

Tools for this decision

Other symptoms