Septic & AWTS Float Switch Australia: Pump-Out, High-Level Alarm & Greywater
Where floats sit in an Australian septic or Aerated Wastewater Treatment System (AWTS), how to spec pump-out control and a high-level alarm, and the heavy-duty IP68 floats that survive dirty, corrosive effluent — for installers, pump shops and on-site sewerage OEMs.
Most Australian homes outside town-sewer reach run an on-site system: a septic tank, an AWTS (aerated wastewater treatment system), or a pump-out well that discharges to drip line, sprinkler or council connection. Every one of these moves liquid on a level, and the level is set by a float switch. A failed or wrongly specified float means a surcharge — effluent at the surface — which is an environmental breach and an expensive cleanup. This guide is for Australian installers, pump resellers and packaged-treatment OEMs specifying level control for 240V single-phase sewage duty.
1. Where the floats sit in the system
A typical AWTS or pump-out installation uses floats in two places:
- Pump well (treatment tank or dosing tank): a low-level float starts the discharge pump, a high-level float stops it. That pair gives the hysteresis so the pump does not short-cycle.
- High-level alarm point: a third float, set above the pump stop point, triggers an audible/visual alarm so an operator is warned before the tank surcharges.
Greywater and stormwater-sumppump reuse systems use the same logic: pump on at low, off at high, alarm above.
2. Pump-out control: start/stop hysteresis
Use two separate cable floats in the pump well — never one float doing both jobs. A low float with a normally-open contact starts the pump when the effluent rises; a high float with a normally-closed contact stops it when the tank is drained to set point. The vertical gap between them sets the pump's duty volume. Two floats cost little and remove the single point of failure that a shared float creates.
3. The high-level alarm is not optional
A dedicated high-level alarm float, wired to an alarm panel (buzzer + beacon) and, where the design calls for it, a backup pump or lagoon, should sit above the pump stop point. Keep it electrically independent from the pump floats: if the pump-control float jams, the alarm still fires. Many Australian states and councils expect a visible high-level alarm on AWTS units, and it is the cheapest insurance against a surcharge callout.
4. 240V pump control in Australia
Septic and AWTS discharge pumps are usually 240V single-phase. A float can switch a small pump directly only within its contact rating (e.g. 10(8) A at 250 V AC); for most duty pumps the float should signal a contactor or pump controller so the contacts only carry the coil. All wiring must follow AS/NZS 3000 (Wiring Rules) with RCD protection on the pump circuit, and the alarm circuit should be on a separate supply so a pump fault cannot take down the warning. We supply the floats; the licensed installer owns the wiring and compliance.
5. Heavy-duty floats for dirty, corrosive duty
Septic and AWTS effluent is dirty, anaerobic and mildly corrosive — exactly the conditions that kill a cheap float. Specify:
- IP68 sealing for continuous submersion, with an oil- and chemical-resistant cable jacket (neoprene or PVC rated for the medium).
- A free-hanging weight so the float cannot be trapped by sludge or rope.
- A contact form that fails safe if the float is blocked — a jammed "off" float is far safer than a jammed "on" float。
- PP body as standard; 316 stainless where the duty is aggressive or high-temperature.
We do not claim WaterMark certification on these floats; whether a specific model is accepted for a given plumbing installation is a question for the specifying plumber and the relevant water authority.
6. Greywater and sump reuse
Greywater diversion pumps, basement sumps and stormwater harvesting pits all use the same start/stop + alarm pattern. The only change is the medium: greywater carries soaps and grit, so favour the heavier jacket and a side-mounted option where a pendant would tangle in a narrow pit.
7. Spec checklist for your RFQ
- System type: septic, AWTS, greywater, or stormwater sump.
- Pump voltage and current (usually 240V single-phase), inrush estimate.
- Number of floats needed: 2 for pump (start/stop) + 1 independent alarm.
- Medium and temperature: dirty/corrosive effluent, ambient range.
- Mounting: cable pendant with weight, or side-mount for narrow pits.
- IP rating (IP68), cable length, and contact form (NO/NC) per job.
ELEHPD supplies heavy-duty cable floats and rod floats in PP and stainless bodies with IP68 sealing, NO/NC contacts and leads sized for direct pump control or contactor signalling, built to IEC practice for sewage and greywater duty when installed by a licensed operator.
FAQ
What float switch do I need for a septic pump-out?
You need at least two heavy-duty cable floats in the pump well: a low-level float to start the pump and a high-level float to stop it, giving the start/stop hysteresis that stops short-cycling. Both must be IP68 with an oil- and chemical-resistant jacket, because septic and AWTS effluent is dirty and mildly corrosive. A third, separate high-level alarm float wired to an audible/visual alarm is best practice so an overflow is caught before it surcharges.
How do I add a high-level alarm to my AWTS or septic tank?
Fit a dedicated high-level float set above the pump stop point, wired to an alarm panel (buzzer and beacon) and, where required, a lagoon or backup pump. Keep the alarm float electrically independent from the pump floats so a pump-control fault cannot also silence the alarm. Many Australian councils require a visible high-level alarm on AWTS installations.
Can one float do both pump control and alarm?
Not safely. Combining pump and alarm on a single float means a stuck or failed float takes out both functions at once. Use separate floats: two for pump start/stop and one independent high-level alarm. The small extra cost is far cheaper than a surcharge callout or an environmental breach.
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Supplying the Australian market
ELEHPD manufactures and wholesales float switches and level controllers to distributors, pump packagers and OEMs. For the Australian market we supply factory-direct with English datasheets and labelling, OEM/private-label options, and short lead times — spares and documentation are supplied from the factory, not from a local warehouse. See our Australia market page for voltage, standard and application notes.
Talk to us about your specification
Send the system type, pump rating and how many floats (pump start/stop + alarm) you need and we will confirm the closest match from the ELEHPD catalogue, the compliance documents available for it and the lead time. OEM branding and buyer-specific cartons are available on qualified volumes.