Grinder vs Drainage Pump: Which One You Actually Need
Written for Australian homeowners, builders and plumbers standing in front of two pumps that look similar and cost wildly different amounts.
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A grinder pump is for sewage and a drainage pump is for clean water. That is the whole answer in one line. A grinder has a cutting mechanism that shreds solids, toilet paper and the wet wipes people swear they never flush, so the waste can be pushed up a narrow pipe. A drainage pump has no cutter. It moves rainwater, groundwater and stormwater at high flow, and it will destroy itself trying to pass sewage. Put the wrong one in and you either burn out a pump or block a pipe. Neither is cheap to fix.
So before you pick, work out one thing: is the water dirty with solids, or is it basically clean?
The short version
Use a grinder pump for anything carrying human waste. Toilets, a granny flat, a basement bathroom, a below-ground laundry that runs to a sewer main. The grinder shreds the solids so a 32mm or 40mm rising main does not block.
Use a drainage pump for anything that is water and not much else. Driveway runoff, a flooded basement, groundwater seepage, a stormwater pit. Higher flow, bigger passage for grit and leaves, no cutter to wear out on clean water.
Same pit, same tank, completely different machine sitting in the bottom of it. That is the part people miss.
What a grinder pump does
A grinder pump cuts solid waste into a slurry, then pumps that slurry up a small-diameter pipe under pressure. The cutting head, a rotating blade against a fixed plate, is the whole point. It lets a 40mm pipe carry sewage that would otherwise need a 100mm gravity line. That means smaller trenches, longer runs and the ability to lift waste up and over obstacles.
Grinders live in sewer pump stations. If the drain sits below the sewer main, or the toilet is in a basement, the waste has to be lifted, and it has to be lifted without blocking. A grinder does both.
The grinder pumps we stock
Waternex carries grinder pumps from compact single-toilet units up to three-phase commercial. Prices current as of July 2026:
- The REEFE REG015 Grinder & Macerator Pump at $1,299 suits a single bathroom or an ensuite lift, the small jobs.
- The REEFE RGM055A Sewage Grinder Pump at $1,590 moves 9,600L/h and is the workhorse for a granny flat or a small dwelling.
- The REEFE RGS11A Automatic Sewage Grinder Pump at $2,135 runs 11,500L/h with a built-in float, so it switches itself on and off.
- The REEFE RGS22M 2.2kW Grinder Pump at $4,287 is three-phase heavy duty for commercial and high-head work.
Most people buying a grinder are not buying a bare pump. They are buying a REEFE RGM055A 250L Sewer Pump Station at $3,349, which is the grinder already fitted into a tank with the valves, pipework and a high-level alarm. That is the normal way to do it.
What a drainage pump does
A drainage pump moves large volumes of relatively clean water and passes small solids like grit, sand and leaves without cutting them. No blade, no fixed plate, just a vortex or open impeller that shifts water fast. That is why a drainage pump is cheaper than a grinder of the same power. There is less inside it to build and less to wear out.
Drainage pumps handle stormwater, groundwater and surface runoff. A vortex design keeps the impeller clear of the debris path, so leaves and grit go through the middle of the flow rather than jamming the blades.
The drainage pumps we stock
Waternex stocks vortex sump pumps sized by flow, all with a vertical float so they run automatically. Prices current as of July 2026:
- The REEFE RVS200VF Vortex Sump Pump at $674 moves 12,000L/h, enough for a domestic pit or a small basement.
- The RVS250VF Vortex Sump Pump at $635 steps flow up to 14,100L/h.
- The REEFE RVS300VF Vortex Sump Pump at $939 hits 18,000L/h for a larger catchment or a heavy runoff area.
For a full stormwater setup, the REEFE Stormwater Pit & Pump comes pre-assembled from $799 in 40L, 85L and 180L, or step up to a Kwikflo 250L Stormwater Pump Station at $2,607 for a bigger job.
Grinder vs drainage pump: the comparison
The table below is the fast version. Match your job to the left column and the pump follows.
| Feature | Grinder pump | Drainage pump |
|---|---|---|
| Handles | Sewage, solids, toilet paper | Stormwater, groundwater, clean runoff |
| Cutting head | Yes, shreds solids | No |
| Rising main | Narrow, 32mm to 40mm under pressure | Wider, lower pressure |
| Flow | Lower, works against high head | Higher, moves big volumes fast |
| Typical price | $1,299 to $4,287 | $635 to $939 |
| Goes in | Sewer pump station | Stormwater pit or pump station |
Prices are Waternex list prices in AUD including GST, current as of July 2026.
How to tell which one your job needs
Ask what is going into the pit. If a toilet, a kitchen sink or a laundry drains into it, you need a grinder. If it is only rain, groundwater or surface water, you need a drainage pump. That single question settles nearly every case.
Jobs that need a grinder
Any fixture connected to the sewer needs a grinder pump. A granny flat with a bathroom and kitchenette. A basement toilet below the main. A garbage room, a laundry, a shop amenities block. Anywhere waste has to be lifted to reach the sewer, the pump has to cut solids, so it has to be a grinder. There is no clean-water shortcut here.
Jobs that need a drainage pump
Clear water with no sewage needs a drainage pump. A driveway that floods in a downpour. A basement carpark taking seepage. A stormwater pit collecting roof and surface runoff. A low section of yard that will not drain. The water is dirty with grit and leaves, not solids, so a vortex drainage pump is the right and cheaper tool.
The one that catches people out
Greywater sits in the middle and usually still wants a grinder-class pump, not a plain drainage pump. Water from a washing machine, shower or sink carries lint, hair and food scraps that a bare drainage impeller can choke on over time. When in doubt on greywater, ask us before you order, because the cheap pump is a false economy if it clogs every month.
What happens when you fit the wrong one
Fitting a drainage pump on sewage blocks the pump and the pipe, fast. A drainage impeller cannot cut toilet paper or wipes, so the passage jams, the motor overheats and the pump trips or burns out. Meanwhile the narrow rising main a plumber sized for a grinder chokes on uncut solids. You get a blocked line and a dead pump in the same week.
Fitting a grinder on clean stormwater is the less dangerous mistake but still a waste. The grinder works, but you have paid two to four times the price for a cutting mechanism that never cuts anything, and its lower flow means it clears a flooding pit slower than a drainage pump would. Right tool, wrong job.
Flow and head still matter after you pick the type
Choosing grinder or drainage is step one, not the whole decision. Once the type is set, size the pump to the head, the vertical lift plus friction loss in the pipe run. A pump rated for 9,600L/h on paper moves far less once it is pushing up six metres and along thirty metres of pipe. Undersize it and the flow drops to a trickle. Our guide on what size sewer pump station you need walks through measuring head in about five minutes, and it applies to both pump types.
New to the whole idea of a pumped system? Start with what a sewage pump station is, then come back here to pick the pump.
Where to buy each in Australia
Buy the pump as part of a packaged station unless you are replacing a failed unit. A packaged station arrives with the correct pump already matched to the tank, valves and alarm, which removes the guesswork. Browse grinder-based Sewer Pump Stations, or clean-water Stormwater Pit and Pump Systems. If you want to see both ranges side by side, the Sewage & Stormwater Pump Stations collection lists them together.
Frequently asked questions
What is the difference between a grinder pump and a drainage pump?
A grinder pump has a cutting head that shreds solids like toilet paper and waste so sewage can be pushed up a narrow pipe, while a drainage pump has no cutter and moves large volumes of clean water such as stormwater and groundwater. Grinders go in sewer stations, drainage pumps go in stormwater pits.
Can I use a drainage pump for sewage?
No. A drainage pump cannot cut solids, so sewage will block the impeller and the rising main, and the motor will overheat and fail. Sewage always needs a grinder or cutter pump built to shred solids.
Do I need a grinder pump for a granny flat in Australia?
Yes, a granny flat connected to sewer needs a grinder pump because the toilet, shower and kitchen waste all carry solids. A 250L sewer pump station with a grinder, such as the REEFE RGM055A package, is the standard choice for a granny flat.
What pump goes in a stormwater pump station?
A drainage pump goes in a stormwater pump station, usually a vortex sump pump. It moves rainwater, runoff and groundwater at high flow and passes grit and leaves without a cutter. It is not built for sewage.
How much does a sewage grinder pump cost in Australia?
A sewage grinder pump costs from about $1,299 for a compact single-bathroom unit up to $4,287 for a three-phase heavy-duty model, as of July 2026. A packaged 250L sewer pump station with the grinder already fitted starts around $3,349.
Not sure which pump your job takes? Ask first
Tell us what drains into the pit, whether it is sewage or stormwater, and the lift to the discharge point, and we will tell you the exact pump. It costs nothing and it is a lot cheaper than pulling the wrong pump back out of the ground.
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This guide is general information for Australian conditions and isn't 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 pump selection, sizing and compliance before you order.