Submersible Pumps for Bores, Sumps and Sewage

A submersible pump sits under the water and pushes it up and out. The motor is sealed, so the whole unit can live in a bore, a pit, a tank or a sewage well. It never needs priming, and the water around it keeps it quiet.

The trick is picking the right type. A bore pump and a sewage pump are both submersible, but swap them and neither will do the job properly. Start with where the pump is going and what's in the water. Then check flow, head and power supply.

Submersible pumps by application

Bore and well pumps

Bore pumps are long, narrow multistage pumps built for clean water and high head. Grundfos SQ and SQE pumps fit bores 3 inches (76 mm) and wider, and have dry-run protection built in. The SQE runs at variable speed, so with its controller it holds steady pressure as taps open and close. Grundfos SP pumps suit 4 inch bores and larger, and move more water for irrigation, stock and farm supply.

Browse the full range of submersible bore pumps.

Sump and drainage pumps

Sump pumps keep pits, sheds, basements, laundries and low yards dry. Most people want an automatic model with a float switch, so the pump turns on when water rises and off when the pit is empty. Stainless steel domestic pumps like the Ebara Best One and Grundfos Unilift KP handle clean to lightly dirty water. If the water carries leaves, grit or small stones, pick a vortex model like the Unilift AP35 or AP50. The impeller sits back out of the flow, so solids pass through instead of jamming it.

Shop sump pumps or the full Grundfos Unilift range.

Sewage and wastewater pumps

Raw sewage, grey water, septic tanks and trade waste need a pump built to handle solids. There are two main types.

• Vortex sewage pumps like the Grundfos SEV and Tsurumi PU series let solids pass straight through. The biggest SEV models pass solids up to 100 mm. They suit sewage pits and pump stations that discharge into larger pipe.
• Grinder pumps like the Grundfos SEG cut solids into a fine slurry. That lets you pump sewage through small pipe over long distances, which is why grinders are the standard pick for pressure sewer systems.

Site drainage and dewatering

Building sites, flooded trenches, excavations and mine pits need a tough portable pump that copes with sand and silt. Tsurumi's HS, LB and KTVE series are built for this work, with automatic versions that switch themselves on and off. For slabs and floors, the Tsurumi LSC pumps water down to around 1 mm, so you can finish the job instead of mopping.

See the full Tsurumi range.

Rainwater tank pumps

A submersible tank pump sits inside the tank, so there's no pump box to build and very little noise. The Grundfos SB is a multistage tank pump with a float switch. The SBA adds an automatic pressure switch, so it starts when you open a tap and stops when you close it.

Pond and water feature pumps

Pond pumps run all day, every day. The Davey Dynapond range is rated for continuous duty and has an adjustable inlet strainer to keep leaves out of fountains and pond filters.

Which submersible pump do I need?

How to size a submersible pump

You need three numbers before you pick a model.

1. Flow. How many litres per minute you need at the outlet.
2. Total head. The height from the water level to the highest outlet, plus friction loss in the pipe, plus the pressure you want at the tap. Every 1 bar (100 kPa) of pressure adds about 10 metres of head.
3. Power supply. Most homes run 240V single phase. Bigger bore, drainage and sewage pumps often need 415V three phase.

Pick a pump that hits your flow and head near the middle of its curve. Too big and it cycles on and off and wears out early. Too small and it never delivers the pressure you need.

For bores, also check the bore diameter, the standing water level and how much water the bore can yield. Never pick a pump that pulls more than the bore can supply. Our bore pump buying guide walks through it step by step.

Reading the model code

Model codes look like gibberish, but they tell you most of what you need.

• Grundfos SP: in SP 5A-12, "5A" is the rated flow in cubic metres per hour and "12" is the number of stages. More stages means more head.
• Grundfos Unilift AP: the number after AP is the largest solid it passes, in mm. An AP12 passes 12 mm and an AP50 passes 50 mm. "A" means a float switch is fitted, a "1" means single phase, a "3" means three phase and a "V" on the end means a vortex impeller.
• Tsurumi: the first number is the outlet size in mm, so a 50PU has a 50 mm outlet. An "A" in the series name (PUA, PNA) means automatic, and an "S" on the end means single phase 240V.

Protect your pump

Running dry, pumping sand and constant short cycling are the usual killers of submersible pumps. A float switch stops a sump pump running dry. A high-level alarm warns you before a sewage or stormwater pit overflows. On bores, dry-run protection and correct sizing do the same job.

Need help choosing?

Send us the job, the flow and head you need, your power supply, and a photo of the old pump's nameplate if you're replacing one. We'll match the right model before you order. Call (08) 6384 5884 or contact the team.

Submersible pump FAQs

What is a submersible pump used for?

Moving water up from places a surface pump can't reach or shouldn't sit: bores and wells, sump pits, sewage and septic pits, stormwater, building site dewatering, rainwater tanks and ponds. For a full walkthrough, read our submersible pump guide.

Is a submersible pump better than a surface pump?

For deep water, yes. A surface pump has to suck water up, and suction lift tops out at around 7 to 8 metres in practice. A submersible pump pushes from below, so depth isn't a problem. It also never needs priming and runs quieter. Surface pumps are easier to reach for servicing and are the better pick for boosting mains or tank pressure. See centrifugal vs submersible pumps.

Can a submersible pump handle dirty water?

Some can. Standard sump pumps handle clean to lightly dirty water. Vortex pumps handle grit, leaves and small solids. Sewage pumps handle raw sewage. Always check the solids passage in mm before you buy. There's more detail in our guide to submersible pumps for dirty water.

Do I need a float switch?

For a sump, drainage or sewage pit, yes, unless someone will switch the pump on and off by hand. Many models come with automatic switching built in, so look for "A" or "automatic" in the name. Bore pumps don't use float switches. They rely on dry-run protection instead, which Grundfos SQ and SQE pumps have built in.

Do you deliver submersible pumps Australia-wide?

Yes. Orders ship Australia-wide. Heavy or oversized pumps may need extra freight, which we confirm with you before dispatch. See our delivery and shipping page for details.