# Radon Manometer Reading Zero? What It Means | Iowa > How to read a U-tube radon manometer, what a level or zero reading means, electronic alarm and error codes, and quick checks before calling. URL: https://iowaradonsystems.com/guide/radon-manometer-zero-reading/ Last-Modified: 2026-10-10 Tags: radon manometer reading zero Radon Guide // Radon System Repairs # Radon Manometer at Zero or Alarm Sounding? What It Means How to read a U-tube radon manometer, what a level or zero reading means, electronic alarm and error codes, and quick checks before calling. Updated October 10, 2026 5 min read By the Iowa Radon Systems team ![Close-up of a U-tube radon manometer with level liquid on a basement pipe](https://placehold.co/1200x630/0b2545/ffffff?text=Close+up+of+U+tube+radon+manometer+with+level+red+liquid+on+white+basement+PVC+pipe+showing+zero+reading) ## Your System’s Health Check Most homeowners only check their mitigation setup during a real estate transaction. That small gauge on the pipe is actually your daily proof of safety. A radon manometer reading zero means your system has stopped pulling dangerous soil gas away from your foundation. We see this happen frequently, and it usually means it is time for a radon system repair [/system-repairs/ →](/system-repairs/) . You can often diagnose the exact issue before scheduling a service call. Let’s look at the data, what your gauge is telling you, and explore a few practical ways to respond. ## How to Read a U-Tube Manometer Learning how to read a radon manometer takes just a few seconds. Most installers use a clear, U-shaped tube filled with a non-toxic blue or red oil, usually a standard Dwyer gauge. One end connects inside the PVC pipe to measure vacuum pressure, while the other stays open to your basement air. Our technicians rely on this visual cue to confirm system performance. A healthy system pulls the liquid higher on the side connected to the pipe. This difference in height shows the exact suction strength, which typically runs between 0.5 and 1.75 inches of water column. You have a problem when you see radon u-tube levels even on both sides. This dead-level state confirms the fan is no longer pulling air. Installers usually mark the initial suction level with a sticker or a sharpie line on the pipe. Always compare today’s liquid height to that original mark. | What you see | What it likely means | What to do | | --- | --- | --- | | Uneven liquid, same as the install mark | Working normally | Check again next month to ensure continuous safety. | | Uneven, but less than the install mark | Weaker suction | Look for a loose lid or new opening; call if it doesn’t improve. | | Uneven, more than the install mark | Higher suction, possible blockage | Check the roof exhaust outlet for ice or debris; call us. | | Both sides level | No suction | Do the quick power checks below, then call for service. | | Liquid missing or tube cracked | Gauge problem | Call to replace the broken manometer immediately. | ## Quick Checks Before You Call Before scheduling a service visit, verify your fan actually has electrical power. Simple tripped breakers or minor winter weather blockages cause many false alarms. We recommend running through a fast diagnostic checklist to save time. These steps cover the most common, easily fixable power interruptions. 1. **Listen for the fan.** Go to the mounting location on your exterior wall or in the attic. You should hear a steady hum and feel a slight vibration on the pipe casing. 2. **Inspect the breaker and GFCI.** Locate your main electrical panel and check for a tripped circuit. Many outdoor fans run on GFCI outlets, which frequently trip during heavy rainstorms. 3. **Check the disconnect switch.** US electrical codes require a shutoff switch within sight of the fan. Ensure nobody accidentally flipped this switch to the off position. ![Electrical disconnect switch next to a radon fan on an exterior wall](https://placehold.co/800x500/0b2545/ffffff?text=Electrical+disconnect+switch+mounted+next+to+radon+fan+on+exterior+wall+of+Iowa+home+with+weatherproof+cover) 4. **Look for roof blockages.** Northern US homes often experience ice buildup at the exhaust point during freezing weather. Frozen condensation will completely block airflow and drop your gauge to zero. 5. **Verify the sump seal.** Plumbers or DIYers often remove the sump pump lid for maintenance. A loose or unsealed lid destroys the vacuum seal your system needs to function. Your fan might have power but still fail to move air. It is definitely time to call a professional if the fan hums but the gauge stays perfectly level. ## Why a Manometer Drops to Zero A radon manometer reading zero almost always points to a mechanical failure or a complete loss of power. The gauge itself rarely breaks, so a flat reading means your underground vacuum seal is compromised. Our repair crews find that dead fan motors account for roughly 80 percent of these calls. Mitigation fans run continuously, and most major brands like RadonAway or Fantech have an expected lifespan of five to ten years. Here is a breakdown of the specific reasons your system stopped working: - **Motor failure.** Continuous, 24/7 operation eventually degrades the internal bearings and ruins the motor. - **Thermal shutdown.** Most modern fans contain a safety switch that triggers if the motor housing exceeds 130 degrees Fahrenheit. The unit might restart after cooling, but frequent overheating signals a failing motor. - **Electrical loss.** A localized power failure or a tripped safety outlet instantly stops the fan from spinning. - **Broken pipe connections.** A cracked PVC joint or a loose rubber coupling completely destroys the underground vacuum suction. - **Gauge malfunction.** The tinted indicator oil can slowly evaporate over a decade. A cracked plastic tube also causes the liquid to drain out completely. ## Electronic Alarms and Error Codes Modern mitigation setups often feature active monitoring devices to alert you instantly when suction fails. You might hear a radon alarm going off before you ever notice a physical change on the plastic gauge. We install these units because they provide immediate auditory warnings for hidden fan failures. Brands like RadonAway Checkpoint or digital Airthings monitors use precise pressure sensors to track airflow. ![Electronic radon system alarm with a warning light on a basement wall](https://placehold.co/800x500/f4f8f8/0b2545?text=Electronic+radon+system+alarm+with+warning+light+mounted+on+basement+wall+near+radon+pipe) You should identify the specific warning type before taking any major action: - **Low-pressure alert:** The sensor detects a drop in suction, meaning the fan stopped or a pipe cracked. - **Battery warning:** Most standalone alarms use standard CR2032 or AA batteries that require replacement every one to three years. - **Sensor blockage:** Dirt or basement condensation can clog the tiny vinyl tube connecting the alarm to the main pipe. - **Elevated gas levels:** Continuous monitors will sound a persistent alarm if the actual gas concentration rises back above the 4.0 pCi/L EPA action level. Always record the exact blinking light pattern or error code on the digital display. This specific information helps diagnostic teams pinpoint the issue over the phone. > **When to call** > > If the quick checks don’t fix it, call our 24/7 support line. Describe what you see and send a photo of the manometer or alarm. We’ll tell you what’s likely wrong and give you a flat-rate repair price before we visit. ## Is It Urgent? A failed mitigation fan does not require an emergency middle-of-the-night service call, but you should not ignore it. EPA data shows that indoor gas levels can return to their original, dangerous concentrations in just 12 to 48 hours after a system stops. We advise homeowners to schedule a repair within a few days of noticing the failure. The health risks accumulate over long-term exposure, so a brief, few-day outage will not cause immediate harm. Plan to conduct a fresh 48-hour indoor air test once the repair is complete. This verification step ensures your restored system is actively pulling enough soil gas to keep your family safe. ## What Happens on the Repair Visit A licensed technician will start by running a diagnostic static pressure test on your entire pipe network. This exact measurement reveals whether the problem is a dead fan, a hidden pipe leak, or a blocked exhaust vent. Our teams arrive with fully stocked trucks to replace faulty motors, rubber couplings, or cracked gauges on the spot. If your equipment is getting old, you should review the options to repair vs. replace the fan [/guide/radon-fan-lifespan-repair-vs-replace/ →](/guide/radon-fan-lifespan-repair-vs-replace/) . You want to ensure the final setup restores full suction and brings that indicator fluid back to the proper level. Do not ignore a radon manometer reading zero for too long. Contact a certified professional today to get your system back online and your home’s air safe to breathe. Quick Answers ## Frequently Asked Questions What should a radon manometer read? When the fan is running, the liquid in a U-tube manometer sits higher on one side than the other. That difference shows the system is pulling suction. Many installers mark the normal level at install. If both sides are level, the system isn't pulling suction. My manometer is at zero. Is the fan dead? Possibly, but check the simple things first. Make sure the circuit breaker is on and the disconnect switch near the fan is on. Listen for the fan. If it's powered and silent, or running but the manometer is still level, call for a repair. Is a zero manometer reading urgent? It's not an emergency, but don't ignore it. Without suction, radon levels can climb back up over the following days. Call our 24/7 support line to book a repair, and plan a radon test if the system was off for a long time. Related Service ## Radon System Repairs Repairs for existing radon systems, including fans, pipes and joints, indicators and error codes. We fix systems we installed and systems other contractors installed. Learn more about Radon System Repairs [/system-repairs/ →](/system-repairs/)