What to Check Before You Buy an Oil Water Separator in Australia
Nine checks before you buy an oil water separator in Australia, in the order they bite. Most of the expensive mistakes happen before the unit is even ordered.
Before you buy an oil water separator in Australia, confirm four things: the peak flow rate reaching the unit, what your water authority wants in the trade waste consent, where the separator physically goes (bund, hazardous zone, pit), and exactly what ships in the box. Get those right and the model picks itself. For most sites that lands somewhere between a $5,927 KCPS-1000 for a single workshop bay and a $9,699 KCPS-3000 for a transport depot.
Skip any of them and you either buy too small, buy too big, or buy the right tank and then discover the pump, panel and pit were never in the price. Here is the list we run through on every enquiry.
1. Know your peak flow rate before you look at tank sizes
Peak flow rate is the single number that sizes an oil water separator, so work it out before comparing models or prices. It is set by how many hoses or bays can run at the same time and by the pump that feeds the separator from the collection pit.
Floor area does not size a separator. Neither does the number of staff, the size of the shed, or what the last tenant had. A 2000 square metre warehouse with one hose tap needs less separator than a two bay truck wash.
If nobody can give you a flow figure, the bay count and wash type get you close enough for a first pass:
| Site | Starting point | Price |
|---|---|---|
| Single service bay, small mechanical workshop, occasional floor washdown | KCPS-1000 | $5,927 |
| Workshop with a dedicated wash area, two bays, light commercial vehicles | KCPS-1500 | $6,720 |
| Busy service centre, plant wash bay, washing that runs most of the day | KCPS-2000 | $8,626 |
| Transport depot, multi bay heavy vehicle wash, large industrial site | KCPS-3000 | $9,699 |
Prices current as of October 2026, AUD including GST. Confirm the required flow rating against your trade waste consent.
Our oil water separator sizing guide walks through the flow logic in more detail if the site is borderline between two sizes.
2. Check what goes into the water, not just how much
Hot water, detergents and heavy silt each push a site up one separator size, regardless of the bay count. Ask the people doing the washing what they actually use, because the answer is often different from what the manager thinks.
Hot water and degreasers emulsify oil. The droplets get smaller and stay suspended longer, so the separator needs more retention time to pull them out. Silt is a different problem: a site washing muddy plant fills the sludge hopper long before the oil side gives any trouble, and a bigger tank means fewer shutdowns to drain it.
One more thing to rule out here. If any of the water comes from a kitchen, that stream does not go anywhere near an oil water separator. Kitchen fat blinds coalescing plates in weeks and belongs in a grease arrestor instead.
3. Talk to your water authority before you order
Your local water authority decides whether you need a separator, what oil and grease limit applies, and what conditions come with the trade waste consent. Buying the separator first and asking the authority second is backwards, and we see it constantly.
Requirements differ between authorities and between states, so do not take a mate's approval letter from another region as gospel for yours. Your hydraulic consultant or licensed plumber usually handles the application. What you want from that conversation is a confirmed flow rating and any specific equipment conditions, in writing, before money changes hands.
4. Plan the bund before the slab goes down
The separator area must be bunded to contain the full separator volume, and that bund has to keep rainwater out of the system. Bunding is one of the most common reasons an install gets delayed, because it is a concrete job that nobody priced.
Rain is the sneaky part. A separator sized for wash water cannot cope with stormwater from an open forecourt. In a downpour the extra flow pushes oily water straight through the plates and out to sewer, which is exactly the breach the separator was bought to prevent. Roof the wash area or divert the clean stormwater away from the collection pit.
5. Account for the Class 1, Zone 2 hazardous area
An oil water separator and its pit are classified as a Class 1, Zone 2 hazardous area, and that zone extends 500mm above the separator. Everything electrical inside that zone has to be rated for it.
That affects where the control panel sits, what the pump motor is rated to, what kind of junction box you use and how the conduit runs. Your electrician and whoever does the hazardous area design need to see the layout early. Moving a switchboard after the fact is not cheap.
Float switches deserve their own mention. They must be oil proof. A standard float sitting in an oily pit degrades, sticks, and then tells your panel the wrong level, which leads to pumps running dry or pits overflowing.
6. Confirm the collection pit and feed pump
Most above ground separators are fed from a collection pit by a pump, and that discharge pit typically needs a minimum 500L working volume. Too small a pit and the feed pump short cycles itself into an early grave.
The KCPS range uses a diaphragm pump on the feed side, which handles oily, silty water far more gently than a centrifugal pump. Gentle matters. A pump that smashes oil into fine droplets on the way in makes the separator work harder than it should. If the pit to separator leg still needs sorting, our water pumps range covers the transfer side.
7. Read exactly what ships in the box
Every Kwikflo KCPS model includes the tank, plate pack, galvanised frame, diaphragm pump and float switch, but only the KCPS-3000 includes a waste oil drum and none of the range includes a control panel as standard. Compare like with like when you line quotes up.
| Included | KCPS-1000 | KCPS-1500 | KCPS-2000 | KCPS-3000 |
|---|---|---|---|---|
| Tank and coalescing plate pack | Yes | Yes | Yes | Yes |
| Galvanised frame | Support frame | Support frame | Support frame | Floor mount frame |
| Diaphragm pump | Yes | Yes | Yes | Yes |
| Float switch | Yes | Yes | Yes | Yes, MAC3 oil proof |
| Waste oil drum | No | No | No | Yes |
| Control panel | Optional | Optional | Optional | Not included, specify separately |
The KCPS-3000 ships without a junction box or control panel on purpose. The panel spec depends on the site's electrical design and any explosion protected rating the hazardous zone calls for, so it gets specified to suit rather than bundled and replaced. Pipework, conduit and the collection pit are separate on every model.
A cheap quote from elsewhere often looks cheap because it is a bare tank. Ask what the number includes.
8. Check access for cleaning and the three outlets
Buy a separator you can actually get into, because the main maintenance job is pulling the plate packs out and washing them with hot water. The KCPS range uses a removable lid on quick release fasteners, and the plate packs lift straight out.
Leave room around the unit. A loaded plate pack from a KCPS-3000 can weigh up to 30kg, so the person lifting it needs space to stand and a plan that is not "just yank it". Check the three outlets too: a 50mm treated water outlet to sewer, a separate 50mm oil outlet to a waste oil container, and a 50mm sludge hopper drain with a PVC ball valve. Each needs somewhere sensible to go.
The oil water separator price guide covers what installation, bunding and electrical typically add on top of the unit itself.
9. Pick a supplier who will chase the paperwork
The right oil water separator supplier in Australia is one who can give you the manufacturer technical drawing, the inclusions list and a delivered price without three follow up emails. Your consultant needs the drawing for the hydraulic design, and the authority may ask for it with the application.
Be aware that Aline publishes full technical drawings for the KCPS-1000 and KCPS-1500, while exact dimensions and flow figures for the KCPS-2000 and KCPS-3000 should be confirmed against the current drawing before a plant room is set out to the millimetre. Ask for it early. We would rather chase a PDF now than watch someone cut a bund that does not fit.
Polyethylene suits the large majority of workshops and wash bays: chemical resistant, UV stabilised, 5mm walls and lid. Stainless steel is available on every model for aggressive chemistry or where a specification demands it. If nobody has told you that you need stainless, you probably do not.
Frequently asked questions
Where can I buy an oil water separator in Australia?
You can buy an oil water separator in Australia from Waternex, which supplies the Kwikflo KCPS coalescing plate range made by Aline Pumps in 1000L, 1500L, 2000L and 3000L sizes from $5,927 to $9,699 including GST. Each unit ships with the tank, plate pack, galvanised frame, diaphragm pump and float switch. Prices current as of October 2026.
How much does an oil water separator cost in Australia?
A Kwikflo KCPS oil water separator costs $5,927 for the 1000L, $6,720 for the 1500L, $8,626 for the 2000L and $9,699 for the 3000L, including GST. Installation, bunding, the collection pit, pipework, electrical work and any control panel are extra. Prices current as of October 2026.
What size oil water separator do I need?
The oil water separator size you need is set by the peak flow rate reaching it, which depends on how many hoses or bays run at once and on the feed pump, not on floor area. As a starting point, a single workshop bay suits 1000L, a dedicated two bay wash area suits 1500L or 2000L, and a transport depot suits 3000L. Hot water, detergents and heavy silt push a site up one size.
Do I need approval to install an oil water separator in Australia?
Yes, discharging oily wastewater to sewer in Australia normally requires a trade waste consent from your local water authority, which sets the oil and grease limit and any equipment conditions. Requirements vary between authorities, so your hydraulic consultant or licensed plumber should confirm the flow rating and conditions before the separator is ordered.
Does an oil water separator come with a pump?
Every Kwikflo KCPS oil water separator includes a diaphragm pump and a float switch, and the KCPS-3000 also includes a MAC3 oil proof float switch and a waste oil drum. Control panels are optional on the KCPS-1000, KCPS-1500 and KCPS-2000 and are not included with the KCPS-3000, where the panel is specified separately to suit the hazardous area rating.
Should I choose a polyethylene or stainless steel oil water separator?
A polyethylene oil water separator suits most Australian workshops and wash bays, using chemical resistant, UV stabilised polyethylene with 5mm walls and lid. Stainless steel is available on every KCPS model and is worth paying for only where the wash chemistry is aggressive or a project specification requires it.
Send us the site and we will size it
Tell us the bay count, whether you use hot water or degreasers, what you are washing and which water authority you are dealing with. We will come back with the model, what is included, and a delivered price, plus the technical drawing if your consultant needs it.
Talk to us about your separator
Contractors should ask about trade pricing, and we offer engineering design support on whole of site drainage packages.
This guide is general information for Australian commercial and industrial sites and is not a substitute for advice on your specific installation. Discharge limits, separator sizing and approval conditions are set by your local water authority through your trade waste consent. Hazardous area classification, electrical work and connection must be carried out by suitably qualified people. Confirm the required flow rating and configuration with your consultant or plumber before you order. Prices and specifications are current at the date of publication and change without notice.