A septic tank alarm going off means your system’s float switch has detected wastewater sitting at a level it shouldn’t be, usually because the pump has stopped working, the tank hasn’t been pumped out, or the drain field can’t absorb any more water. It’s a warning, not a false alarm, and ignoring it is what turns a simple fix into an overflow.
Here’s what actually triggers a septic alarm, how to tell if it’s an emergency, and what to do in the first ten minutes before you call a professional.
What Does It Mean When Your Septic Tank Alarm Goes Off?
A septic alarm going off means a float switch inside your tank or pump chamber has detected wastewater above its normal operating level and triggered a warning light, siren, or both. You’ll also hear this called a high level alarm or high water alarm; they’re the same thing. It’s an early warning system, designed to flag a problem before wastewater backs up into your house or overflows into your yard.
Most residential systems with a pump (this includes AWTS units and any standard septic tank with an effluent or dosing pump) have at least one float switch wired to an alarm box, sometimes called the septic tank alarm system or control panel, usually mounted on an outside wall near the tank or in the garage. When the float rises past its set point, the alarm fires immediately, regardless of the time of day.
6 Common Reasons Your Septic Alarm Is Going Off
| Cause | What’s Happening | Urgency |
|---|---|---|
| Pump failure | The effluent or dosing pump has stopped working, so wastewater keeps rising with nowhere to go. | High |
| Power interruption | A tripped breaker, blown fuse, or brief outage has stopped the pump, even though it isn’t faulty. | Medium |
| Tank overdue for a pump-out | Solids have built up to the point where there’s no working capacity left to absorb normal use. | Medium |
| Saturated drain field (leach field) | Heavy rain (common across the Mid North Coast) has waterlogged the soil, so it can’t accept water as fast as the system is producing it. | Medium |
| Clogged outlet filter | A blocked filter slows outflow, so the tank fills faster than it drains. | Medium |
| Faulty float switch | The float itself is stuck, tangled, or damaged, and is triggering the alarm even though water levels are otherwise normal. | Low |
Excessive water use on top of any of the above, back-to-back laundry loads, long showers, or a leaking toilet, can also push a system that’s already borderline over the edge.
Is a Septic Alarm Going Off an Emergency?
A septic alarm going off is an emergency if it’s paired with slow or backed-up drains, sewage odours, or wet patches near the tank or drain field, since these signs mean wastewater is already at capacity. If the alarm sounds on its own with no other symptoms, it’s still urgent, but you generally have a short window to act before it becomes one.
What to do in the first ten minutes:
- Stop using water immediately: no laundry, dishwasher, long showers, or multiple toilet flushes. This buys time and stops the level rising further.
- Check the alarm box for a reset or silence button. Silencing the alarm is fine; it does not fix the underlying problem, so don’t mistake quiet for solved.
- Check your switchboard for a tripped breaker on the pump circuit. If it’s tripped and won’t stay reset, stop; this is an electrical fault and not something to keep testing yourself.
- Look for visible signs of overflow: wet ground, pooling, or odours near the tank or drain field. If you see any of these, treat it as an emergency and call us straight away.
- Call a licensed septic professional: if the alarm doesn’t clear within a few hours, or immediately if you’ve spotted an overflow. Don’t wait it out overnight hoping it resolves itself.
Never open the tank lid or attempt to inspect the pump yourself. Septic tanks carry both electrical and biohazard risks, and pump chambers are confined spaces that should only be entered by a trained technician. A sewage backup or septic tank overflow is a health hazard, not a DIY job.
On-site sewage systems (including AWTS) are regulated in NSW, and NSW Health requires council accreditation for anyone servicing or approving these systems, which is exactly why alarm faults need a licensed contractor rather than a guess-and-check approach.
AWTS Alarms vs Standard Septic Tank Alarms
An AWTS alarm can be triggered by more than just high water, including a failed aerator or blower, a fault in the UV or chlorine disinfection unit, or an electrical fault in the control panel, on top of the same high-water and pump issues a standard septic system faces. Because an AWTS has more moving and electrical parts than a standard tank, the range of possible causes is wider, which is exactly why AWTS servicing and repairs need a technician who’s set up to work on the electrical side as well as the plumbing. Skipping scheduled AWTS servicing is one of the most common reasons the alarm goes off in the first place.
When to Call a Professional
Call a professional as soon as a septic alarm goes off alongside slow drains, odours, or wet ground, or if a standard alarm hasn’t cleared within a few hours of reducing water use and checking the breaker. Trying to keep a system limping along past this point usually turns a straightforward callout into an overflow that costs far more to clean up and repair.
If your Valla Beach, Nambucca Heads, or wider Mid North Coast property has an alarm sounding right now, get in touch for emergency septic repairs or call 0402 824 153 directly. Our team includes both licensed plumbers and electricians in-house, so whether the fault is a seized pump, a wiring issue, or a control panel fault, we can diagnose and fix it on the one visit.
How to Stop Your Septic Alarm From Going Off Again
Regular servicing and pump-outs are what prevent most alarm call-outs before they happen. Keep to your system’s recommended schedule (typically every 12–24 months for a standard tank, and every 3–6 months for an AWTS), watch your household water use if you know your system is near capacity, and get any slow drains or odours checked before they turn into an alarm going off at 11pm.
Frequently Asked Questions
How do I reset a septic tank alarm?
Most alarm boxes have a silence or reset button that stops the siren, but resetting it doesn’t fix the cause, the float switch will simply re-trigger once the water level rises again if the underlying problem (pump failure, full tank, saturated drain field) hasn’t been resolved. Treat the reset button as a snooze, not a repair.
What does a flashing red light on my septic alarm mean?
A flashing or solid red light means the float switch has detected high water level or a fault, the same trigger as the audible alarm. Treat it the same way: reduce water use and get it checked if it doesn’t clear.
Can I just turn off my septic alarm and ignore it?
You can silence the audible alarm, but this doesn’t fix the underlying issue, the float is still detecting a problem and it will keep re-triggering until the cause is resolved. Ignoring it risks a sewage backup or overflow.
How long can I leave a septic alarm going off before it’s a problem?
Treat it as urgent from the moment it sounds. If it hasn’t cleared within a few hours of reducing water use and checking your breaker, or if you notice any wet ground or odours, call a professional immediately rather than waiting.
Is it safe to shower or use the toilet while my septic alarm is going off?
Minimise water use as much as possible until the system is checked. Light, essential use is usually fine short-term, but avoid laundry, dishwashers, and long showers, as extra water is exactly what pushes a borderline system into an overflow.
Why does my septic alarm go off after heavy rain?
Heavy rain can saturate the drain field so it can’t absorb wastewater as fast as usual, or it can cause groundwater to seep into the tank, both of which raise the water level enough to trigger the float switch. This is common across the Mid North Coast during wet weather.
Do I need an electrician or a plumber to fix a septic alarm fault?
It depends on the cause, a electrical fault needs an electrician, a pump or blockage needs a plumber, and many AWTS faults need both. Mid Valley Septics has licensed plumbers and electricians in-house, so we can diagnose and fix either type of fault on the same visit.
Septic alarm going off right now? Contact our team for emergency repairs across Coffs Harbour, Valla Beach, Nambucca Heads, and the wider Mid North Coast. We’re fully licensed plumbers and electricians, working in-house with no subcontractors.