Single vs Dual Pump: When You Need a Backup
Written for Australian plumbers, builders and property owners deciding whether the second pump is worth paying for.
Want your exact size? Our pump station sizing calculator works out the tank, pump head and flow from who the station serves and how high and far it pumps, then shows the stations that fit.
A dual pump station is a pump station with two pumps in the one tank, run by a control panel so that if one pump fails or the inflow spikes, the second pump takes over and the tank keeps emptying. You need one when a failed pump would shut the site down, flood something expensive, or affect people who did not choose the risk. For a single house or a granny flat, a single pump with a high level alarm is usually enough.
That covers most calls we get. The rest is where people get it wrong.
What a dual pump station actually does
A dual pump station gives you redundancy: two pumps, one float set, one control panel deciding which pump runs. The usual arrangement is called duty/standby. One pump does the work, the other waits, and the panel switches over automatically if the duty pump stops pumping or the level keeps rising.
Many dual panels also alternate the duty pump between cycles, so both pumps wear evenly instead of one doing all the work while the other sits idle and seizes. The BlueSelect 700L panel, for example, is sold as duty/standby with automatic changeover. Check the panel spec on whichever unit you buy.
The second pump also helps on inflow. If both bathrooms, the laundry and the dishwasher dump at once, a panel with an assist float can bring the standby pump in alongside the duty pump until the level drops.
When a single pump is fine
A single pump station is fine for one household where a failure means inconvenience, not damage. A granny flat, a basement bathroom, a laundry below the main, a single dwelling pump away. If the pump dies, the high level alarm goes off, the family stops using water for a day, and a plumber swaps the pump.
That is a bad day. It is not a disaster.
Most of these sites are served well by a 250L or 900L single station. Our 250L versus 900L versus 1200L comparison covers which size. The options:
- Kwikflo 250L Sewer Pump Station, priced by state from $3,199
- REEFE RGM055A 250L Sewer Pump Station, $3,305
- Kwikflo 900L Sewer Pump Station, $4,699
- Kwikflo 1200L Sewer Pump Station, $4,999
The one thing a single pump station must have is an alarm that someone will actually hear. A single pump with no alarm is how basements flood. If yours is already beeping, read what a pump station alarm actually means.
When you need a dual pump station
You need a dual pump station when the cost of the tank overflowing is far bigger than the cost of a second pump. In practice that means these sites:
- Multiple dwellings on one station. Units, townhouses, duplexes sharing a pit. One failure affects several households, and they did not sign up for it.
- Commercial sites that stop trading. Cafes, offices, medical suites, childcare. No toilets means no staff and no customers.
- Anything below finished floor with nowhere to overflow. Basement car parks, below ground amenities, sites where a surcharge goes straight into a habitable room.
- Sites nobody visits often. Holiday houses, sheds, rural amenities blocks. A single pump can fail on day one of a three week absence.
- When the approval says so. Some water authorities and hydraulic designers require dual pumps above a certain number of connections or for certain building classes. That is set locally, so your plumber or hydraulic consultant confirms it.
If a site hits any of those, stop debating. Buy the dual.
What a dual pump station costs compared to a single
A dual pump station costs roughly $1,000 to $4,000 more than the equivalent single, depending on tank size, pump type and power supply. The real numbers from our range:
| Station | Pumps | Pump | Power | Price |
|---|---|---|---|---|
| Kwikflo 900L single | 1 | ALC750 cutter | 240V | $4,699 |
| Kwikflo 900L dual | 2 | ALC750 cutter | 240V | $5,716 |
| Kwikflo 900L dual | 2 | ALG1500 grinder | 415V | $8,495 |
| Kwikflo 1200L dual | 2 | ALG1500 grinder | 415V | $9,327 |
| Kwikflo 2000L dual | 2 | ALG1500 grinder | 415V | $11,028 |
| BlueSelect 700L single | 1 | 1.1kW grinder | 240V | $4,154 |
| BlueSelect 700L dual | 2 | 1.1kW grinder | 240V | $7,874 |
Waternex list prices in AUD including GST, current as of September 2026. Installation, excavation and electrical work are extra.
Put the Kwikflo 900L single and dual side by side and the backup costs about $1,017. One overflow into a unit block's basement costs more than that in carpet alone. For a shared or commercial station, the maths is not close.
The two dual lines are here: the Kwikflo Dual Sewer Pump Station in 900L, 1200L and 2000L, and the BlueSelect 700L Dual Pump Station in 1.1kW or 1.5kW.
Check the power supply before you pick a dual station
Most larger dual grinder stations run on 415V three phase power, and most Australian houses only have 240V single phase. This catches people every month. In the Kwikflo dual range, only the 900L with ALC750 cutter pumps runs on 240V. The 900L, 1200L and 2000L grinder versions are all 415V.
The BlueSelect 700L dual is the exception worth knowing: it comes in 240V single phase at both 1.1kW and 1.5kW, so a site without three phase can still get grinder pumps in a dual configuration.
Ask your electrician what the site has before you order. Getting three phase connected to a house is a separate job with its own cost and wait time.
Cutter or grinder in a dual station
A cutter pump suits most domestic sewage in a dual station, and a grinder pump is the step up for long discharge runs and higher head. The cutter shreds solids at the intake. The grinder reduces waste to a fine slurry that travels further through smaller pipe.
The ALC750 cutter fitted to the Kwikflo 900L 240V dual is rated to 14 metres of head and 420 litres per minute. If your lift and pipe run sit well inside that, the cutter version is the sensible buy. If you are near the limit, go grinder. Work the number out properly first with our guide to calculating head height for a pump station.
Never put drainage pumps on sewage duty, single or dual. They block. Stormwater is a different product: the Kwikflo Dual Stormwater Pump Station starts at $5,297 for the 900L 240V version.
What a dual pump station does not protect you from
A dual pump station does not protect you from a power outage. Both pumps run off the same supply. If the grid drops during a storm, both pumps stop, and storms are exactly when stormwater stations get busy.
It also does not protect you from a blocked discharge line, a stuck float or a tripped circuit breaker on the shared panel. For real resilience on a critical site, add a high level alarm with a remote or monitored signal, a dedicated circuit, and a generator inlet or battery backup. Your electrician and hydraulic consultant specify those.
And the tank size still matters. The volume above the alarm float is your emergency storage, the time you have between the alarm and an overflow. Bigger tank, more time.
The spare pump on the shelf
A spare pump on the shelf is a cheaper halfway option for a single house that wants faster recovery without a dual station. Buy a matching pump, keep it on site, and a plumber can swap it the same day instead of waiting on freight. It does nothing while you are away or asleep, which is the whole reason dual stations exist.
For a house, it is a reasonable compromise. For a unit block, it is not. Pumps wear out on a schedule, covered in our guide to how long a sewer pump station lasts.
Frequently asked questions
Do I need a dual pump station for a house in Australia?
Most single houses in Australia do not need a dual pump station. A single pump with a high level alarm is normal for one dwelling. Go dual if the station serves more than one dwelling, sits below habitable rooms with no overflow path, or your water authority or hydraulic design requires it.
What does duty/standby mean on a pump station?
Duty/standby means one pump does the pumping while the second pump waits, and the control panel switches to the standby pump automatically if the duty pump fails or the level keeps rising. Many panels also alternate the duty pump so both wear evenly.
How much more does a dual pump station cost?
A dual pump station costs about $1,000 to $4,000 more than a comparable single station in our range. The Kwikflo 900L sewer station is $4,699 single and $5,716 dual with 240V cutter pumps, prices current as of September 2026.
Can a dual pump station run on 240V single phase power?
Yes, some dual pump stations run on 240V single phase. The Kwikflo 900L dual with ALC750 cutter pumps and the BlueSelect 700L dual are both available in 240V. The larger Kwikflo dual grinder stations need 415V three phase.
Will a dual pump station keep working in a blackout?
No, a dual pump station stops in a blackout because both pumps share the same power supply. Critical sites need a generator inlet or battery backup, plus enough tank volume above the alarm to hold the inflow until power returns.
Send us the site details
Tell us how many dwellings or fixtures feed the station, the lift to the main, the length of the discharge run and whether the site has three phase. We will tell you if single is enough or dual is worth it, and which unit fits.
Get a pump station quote for your site
Building or plumbing trade? Ask about trade pricing, or browse the wider Packaged Pump Stations range.
This guide is general information for Australian conditions and is not a substitute for advice from a licensed plumber. Pump station installation and sewer connection are regulated work, and requirements differ between states and water authorities. Have your plumber confirm sizing, approvals and compliance before you order.