Introduction
If the alarm on your ultraviolet (UV) water treatment system has gone off, it’s more than just an annoying sound, it could mean your water is no longer being properly disinfected. In this article we’ll walk you through what the alarm might signify, what to check first, and when to call in the professionals. Whether you’re a homeowner or operate a commercial site in New Zealand, you’ll get practical steps to protect your water supply.
Why the Alarm Matters
When a UV system alarm goes off, it indicates one of several possible faults. According to the Drinking Water Quality Regulator for Scotland (DWQR), UV units often include intensity monitors and alarms that will interrupt water flow if UV radiation falls below safe levels. Also, Western Australia’s Department of Health advises that UV light disinfection only works if conditions are right: clear water, intact lamp, correct flow and no power interruption. In other words, a sounding alarm may be telling you do not use the water for drinking until the issue is resolved.
5 Checks to Perform Right Away
Here are five critical checks you should carry out when your UV system alarm activates.
1. Check the power supply and system indicators
Ensure the UV unit is powered and the status indicators appear normal (e.g., green light, no fault display). A power interruption or fault in the ballast can trigger the alarm.
2. Inspect the UV lamp and quartz sleeve
If the UV lamp has burned out, or the quartz sleeve is fouled, the UV dose drops and the alarm may activate. Lamp-timer expiry and dirty components are common causes of alarm activation.
3. Confirm upstream water quality and filtration
UV systems are very sensitive to water clarity and pre‑treatment. Suspended particles, iron, manganese or turbidity can reduce UV effectiveness and trigger alarms.
4. Check the sensor or monitoring module
If your system includes a UV intensity sensor or flow sensor, ensure it is clean and functioning. Some devices alarm when sensor readings drop below thresholds, indicating potential untreated water risk.
5. Review service history and timer resets
If the lamp was recently changed, has the timer been reset? If the unit has run close to recommended lamp hours (typically ~12 months), an alarm may be triggered as a reminder or warning of reduced performance.
Not sure what’s going on with your UV System?
No worries—give us a call on 0800 278 288. Tell us what you’re seeing and Troy, our qualified plumber will translate the symptoms, talk you through a couple of safe quick checks, and—if a visit makes sense—get a tech on the way.
What You Should Do Immediately
- Stop drinking the water until the alarm issue is resolved.
- Turn off the water supply to the UV system if the alarm indicates a serious fault (e.g., low UV intensity).
- Run the checks listed above in a safe and methodical way (ensure power is off when inspecting lamp or quartz sleeve).
- Record any error codes or alarm messages from the controller, these are helpful for a service technician.
- Contact a specialist if you’re uncertain or cannot restore normal operation.
If you own a Greenway UV water filtration system, we’ve put together a dedicated guide just for you. Learn why Aquaworks is the trusted choice across Auckland for Greenway system servicing. From expert diagnostics to tailored maintenance, we cover it all in our article: 5 Reasons to Choose Aqua Works for Your Greenway UV Water Filtration System Service.
Have an emergency?
We have an emergency 24/7 Call Out service – call this number 0212787427
When to Call a Professional (like Aqua Works)
If you have performed the checks and the alarm remains, it’s time to call the experts. Issues such as ballast failure, sensor malfunction, or major water‑quality faults will require specialist tools and expertise. For reliable service throughout Auckland and the North Shore, contact Aquaworks for full system diagnostics, repairs or replacement of components.
Preventive Measures to Avoid Future Alarm Events
- Replace the UV lamp at the manufacturer‑recommended interval (commonly every 12 months).
- Clean the quartz sleeve and inspect O‑rings / seals regularly.
- Maintain upstream filtration to reduce turbidity, iron, manganese and tannins.
- Test water clarity and UV transmissivity annually or after any water supply change.
- Keep a maintenance log with component replacement dates and service visits.
For a deeper look at how to properly service your UV system, check out our in-depth guide: UV filter maintenance – how to service your UV system. This article walks you through essential upkeep tasks to ensure your filtration system operates at peak performance year-round.
Frequently asked questions
Q1: If the alarm goes off, is the water automatically unsafe?
Not always, but it could be. Alarm systems are designed to show when UV dose or flow is out of spec. Until the fault is rectified, you should assume that water may not be properly disinfected.
Q2: Can I silence the alarm and carry on using the water?
Only after you’ve identified and resolved the cause. Silencing the alarm without fixing the issue can lead to unsafe water use.
Q3: How long should I wait before using the water again after an alarm?
You should wait until the fault has been corrected and the system is back in normal operation. If in doubt, run the system for a few hours and get the water tested.
Q4: What if my alarm keeps going off even after replacing the UV lamp?
This could indicate sensor or ballast faults, incorrect timer resets, or sleeve fouling. A technician can diagnose the exact issue.
Can I test my water to confirm if UV treatment is working?
Yes, regular microbial testing can confirm water safety. Aquaworks can assist with water testing services in the Auckland region.
Why Warkworth homeowners choose Aqua Works
We work on rainwater and bore setups every day across Warkworth, Matakana, Snells Beach, Omaha, Leigh, Puhoi and the Mahurangi area. Our vans carry standard parts (switches, valves, seals, cartridges), so many callouts are fixed on the first visit. We provide transparent pricing, friendly advice, and fit the right pump for your property—not just the biggest one on the shelf.
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- Emergency repairs & diagnostics
- Routine servicing & filtration
- New pump supply & installation (including constant-pressure/VSD systems)
- Tank upgrades, suction improvements, and dry-run protection
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Out of water—or keen to upgrade?
Call Aqua Works on 0800 278 288 or email us on healty@aquaworks.co.nz and we’ll get you sorted.
Water pump failures are stressful, but most are fixable with simple steps or a targeted repair. If the checklist doesn’t bring your system back, we’ll come to you—diagnose, fix, or replace—and make sure it’s set up to stay reliable.