System indicator · source-linked
How to Read a Radon System Manometer
Use the system label and baseline to check a U-tube radon manometer without mistaking pressure indication for a radon measurement.
Direct answer
A radon manometer shows pressure difference, not the radon level. Compare its current columns with the installer-marked normal reading. Equal columns, a major change, missing fluid, or an alarm means the system needs inspection; confirm indoor performance with a radon test.
Reviewed September 5, 2026. United States federal guidance. Device instructions and applicable state requirements take precedence.
Evidence standard
Built from the official primary guidance linked on this page.
Source check
Reviewed September 5, 2026 · maintained by RadonVerdict.
Ten-second visual check
Read the shape, then compare the baseline
The drawing is a status guide, not a target pressure chart. Your installer's mark and an indoor radon test are the controlling evidence.
Uneven, near the mark
The system is showing a pressure difference. Record it, but do not treat it as a radon concentration.
Equal or zero
No pressure difference is being displayed. Check the system record and contact the installer or a qualified mitigator.
Changed or damaged
A material change, missing fluid, loose tube, or alarm is a service signal—not a diagnosis to repair from a web page.
The gauge does not display pCi/L
The common U-tube indicator shows pressure created by an active soil-depressurization system. Its fluid-column difference is evidence about system operation, not a direct measurement of radon in room air.
Do not translate inches of water column into a radon concentration. They are different measurements answering different questions.
Use the system's own marked baseline
Installers commonly mark the expected operating position on or beside the gauge. Compare current status with that documented baseline because fan, pipe, and foundation designs differ between systems.
A generic internet photo cannot establish the correct number for your installation. Preserve the label, installer's contact information, and commissioning record.
A zero or changed reading is a service signal
If the columns are level, fluid is missing, tubing is damaged, an alarm is active, or the reading differs materially from its mark, check the system documentation and contact the installer or qualified mitigator.
Do not open electrical equipment, resize a fan, disconnect piping, or add fluid based on this page. Those actions require system-specific diagnosis.
Only retesting verifies indoor radon control
EPA tells owners to check the warning device regularly and to retest a mitigated home at least every two years. Both checks matter because one does not replace the other.
Record the gauge status when a radon test begins and ends. If the system changed during the exposure, keep that event with the result.
Turn this page into evidence
Build a procedure record
Check only what you can confirm. The summary keeps unresolved items visible instead of converting uncertainty into a pass.
Open the full test plannerCommon questions
Quick answers
Should both sides of a radon manometer be equal?
On a running system, equal columns can indicate no measured pressure difference. Compare with the installer mark and contact the installer rather than assigning a universal target.
What number should my radon manometer read?
There is no single correct reading for every system. Use the commissioned baseline for that installation.
Does the manometer tell me my radon level?
No. It shows pressure difference. A radon test measures the indoor radon concentration.
Evidence boundary
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