Treatment plant alarm sounding? What it means and what to check

The two alarms

Most home sewage treatment plants have two alarms. Many control panels show which one is active, and most have a buzzer and a warning light, with a button to silence the buzzer.

High water alarm. The tank is filling because treated water is not leaving the system. This very often relates to the irrigation pump not pumping out.
Air alarm. The blower is not delivering enough air. The bacteria that treat your wastewater need that air, and without it they die off and the plant begins to smell.

Safe checks, in order

Check the power. Confirm that the plant’s power point and the circuit breaker at your switchboard are switched on.
High water alarm: check the irrigation. Check that the irrigation pump is plugged in and switched on, and that the irrigation hose is not kinked or crushed. Reduce water use, including washing, the dishwasher and long showers, until the problem is resolved.
Air alarm: check the blower. The blower should be running and delivering air. If it is silent, check that it is plugged in and switched on. Occasionally the small hose to the alarm’s pressure switch comes loose: if you can see that it has come off, push it back on.

Do not open electrical components

Stay with the checks above. Anything involving wiring, the control box or the blower’s internals should be left to a licensed technician or electrician.

What not to do

Do not switch the plant off to stop an alarm, or leave it switched off. The blower needs to run continuously.
Do not ignore the warning light. You may silence the buzzer, but a plant can overflow within hours to days.

When to call

If the alarm is still sounding after these checks, call us on 0495 096 532. If the plant is overflowing, has a strong odour or effluent is pooling, please call rather than sending an enquiry.

Callouts are $110 on weekdays ($160 weekends, $220 public holidays), plus any parts, and labour is $80 an hour. We explain the problem and quote before any repair or part, and no work proceeds without your approval. We carry common replacement irrigation pumps and air blowers, so many repairs can be completed on the first visit. Electrical work that requires a licensed electrician is outside our scope, and we will advise you if one is needed.

After a power outage or storm

Leave the plant switched on when you go away. After a long power outage or a severe storm, check the alarm light once power is restored, and call us if it is on or you notice an odour.

See also: repairs and fault diagnosis for the faults we fix, and how to look after your treatment plant to help prevent alarms.

By Joshua Smith, QBCC licence PD52825. Updated 20 October 2026.

Treatment plant alarm sounding? What it means and what to check