An aerated wastewater treatment system (AWTS) is an electrically powered treatment plant, not a passive tank, so a power outage stops it working the moment the lights go out. Storm-related blackouts are common across the Hastings during wet-season low-pressure systems and east coast lows, exactly when a lot of AWTS owners are also dealing with saturated ground, so this guide sets out what actually stops when the power drops, what keeps happening regardless, and what to check once power comes back on.
What actually stops when the power goes out?
An AWTS relies on electricity to run three separate jobs: the air pump or blower that feeds oxygen to the treatment bacteria in the aeration chamber, the irrigation pump that sends treated effluent out to the dispersal area, and the control panel that monitors the whole system and triggers the alarm if something’s wrong. All three stop the instant power is lost. There’s no battery backup on a standard domestic AWTS, and no manual override that keeps treatment running during an outage.
The air pump stopping is the part that matters most. The bacteria doing the actual treatment work in the aeration chamber need continuous oxygen, and they start to die off within hours of the blower stopping, faster in warm weather, more slowly in cool conditions. A short outage of an hour or two generally isn’t a problem: the bacterial population dips but recovers once aeration resumes. A prolonged outage, the kind that can follow a serious storm when a whole area is off grid for a day or more, is a different situation, and the treatment quality your system produces afterward may be reduced until the bacterial population re-establishes itself.
The irrigation pump stopping means wastewater simply isn’t being dispersed. Wastewater entering the system during the outage still flows into the primary chamber as normal, gravity handles that part regardless of power, but nothing is pumped out to the irrigation area until power returns. On a short outage this just means the system briefly holds more volume than usual. On a longer outage combined with continued household water use, the system can back up toward capacity.
The alarm and control panel go dark too, which means an AWTS that develops a genuine fault during the outage, a stuck float switch, a component that doesn’t restart cleanly, may not visibly alert you the way it normally would. That’s exactly why a check once power is restored matters, rather than assuming everything picked up where it left off.
What keeps working regardless of power?
The primary settling chamber keeps receiving and settling wastewater by gravity throughout an outage, the same as it would in a conventional septic tank. Solids still settle to the bottom and the scum layer still forms on top; none of that depends on electricity. This is the reason a short-to-moderate outage is rarely an emergency on its own: the system has spare capacity built in, and normal treatment simply resumes once power is back and the pumps restart.
What should you do while the power is out?
- Cut back water use for the duration of the outage, particularly if it looks like being an extended one. Every litre sent down the drain during an outage is adding to a system that currently has no way to disperse treated effluent.
- Don’t run the washing machine or dishwasher if you can avoid it. These send a large volume through in a short burst, exactly the load the system is least able to absorb with the irrigation pump offline.
- Keep an eye out for surface pooling near the irrigation area. If wastewater starts surfacing before power returns, that’s the point to stop all water use and treat it as urgent regardless of how long the outage has been running.
What should you check once power comes back on?
Don’t assume the system has simply picked back up where it left off, particularly after an outage of more than a few hours.
- Check the control panel and alarm. Confirm the panel has power and isn’t showing a fault light. A unit that restarts cleanly usually shows nothing unusual within the first hour or two.
- Listen for the blower. The air pump should be audible once running, a faint, steady hum near the tank is normal. Silence, or a different noise than usual, suggests it hasn’t restarted properly.
- Check the irrigation area for pooling. If wastewater backed up during the outage, the irrigation pump clearing that backlog once power returns can mean a temporarily heavier discharge to the dispersal area. Some transient dampness is normal; standing water that doesn’t clear within a day is not.
- Extend water-conservation habits for a day or so afterward, particularly following a longer outage, to give the system a chance to work through anything that built up while it was offline.
- If the alarm is on and stays on, treat it as a genuine fault rather than an outage artefact. A float switch, pump or blower can fail during a power event and not recover on its own once electricity returns.
Is a power-outage AWTS issue ever a genuine emergency?
Usually not on its own. A short-to-moderate outage followed by a clean restart is the most common outcome, and it doesn’t call for an urgent visit. Two situations do warrant treating it as urgent: visible sewage pooling or surfacing near the irrigation area at any point, and an alarm that stays active once power has been restored for a reasonable period. Both point to something beyond the outage itself needing attention.
Power outages during storms often overlap with the exact conditions covered in our wet season septic checklist, sustained rain, saturated ground and reduced dispersal capacity, all arriving at once. If your AWTS alarm comes on during or after a major storm and there’s also visible overflow, our emergency septic overflow health risks guide covers the health risks and the immediate steps to take, since an active overflow is treated as an emergency regardless of what caused it.
What does an AWTS check after a power outage cost?
| Scenario | Indicative price | Notes |
|---|---|---|
| Routine check-up after an outage, no visible issues | $150-$300 | Confirms restart, blower, alarm and irrigation area |
| AWTS scheduled service (per visit) | $180-$330 | Standard regional rate if a routine visit is also due |
| Emergency call-out for active overflow or a fault that won’t clear | $400-$800+ | Priced as a standard job plus the usual urgent/after-hours premium |
These are indicative guide ranges only, confirmed once we know your system and, where relevant, have sighted it.
Power outage AWTS FAQs
Will a short power outage damage our AWTS?
No, not typically. A brief outage of an hour or two causes a temporary dip in the aeration chamber’s bacterial activity, but it recovers once the blower restarts. The system’s mechanical components aren’t damaged by the outage itself.
Our power was out for two days during a storm. Should we get the system checked?
Yes, that’s worth a check-up rather than an assumption. An extended outage affects treatment quality for longer while the bacterial population re-establishes, and it’s also long enough that a genuine fault could have developed without the alarm being visible to you at the time.
Can we still use water at all during a power outage?
Minimally, yes, the primary chamber keeps settling solids by gravity regardless of power. But cut back hard: no washing machine or dishwasher, shorter showers, and spread out anything unavoidable, since the irrigation pump isn’t dispersing anything until power returns.
The alarm went off during the outage and is still going now that power is back. What does that mean?
Treat it as a genuine fault rather than something the outage will fix on its own. A float switch, pump or blower can fail during a power event without recovering when electricity returns, and it’s worth booking a service rather than waiting to see if it resolves.
Do generators help during an extended outage?
A generator can keep the blower and irrigation pump running if you have one connected, which avoids the whole issue. For anyone on a property prone to frequent or extended outages, particularly in the more remote parts of the Hastings hinterland, it’s worth discussing with an electrician whether the AWTS circuit can be included on a backup supply.
Get your AWTS checked after an outage
If your power’s been out for an extended stretch, the alarm won’t clear once electricity is back, or you’ve seen any pooling near the irrigation area, get a free quote and ask for a check-up. Tell us how long the outage ran and what the panel and alarm are showing now.