Submersible Pump FAQs
Reviewed by Chris Raven, Auckland Branch Manager, Pumps Online
What is a submersible pump?
A submersible pump is designed to operate while fully immersed in water. Depending on its design, it may be used for clean water, rainwater, stormwater, dirty water, grey water, sewage, effluent, household supply, irrigation or water transfer.
Not every submersible pump can handle the same water type or solids, so select a model designed for the intended application.
These frequently asked questions explain how to size, select, install and troubleshoot a submersible pump.
Choosing & Sizing a Submersible Pump
How Deep Can a Submersible Pump Go?
It depends on the type and model of pump.
Submersible pumps designed for clean water, dirty water, grey water or sewage may have maximum immersion depths of approximately 5–12 metres.
Bore pumps are designed for much deeper applications, with some operating hundreds of metres below ground.
Always check the pump specifications or ask for advice before selecting a pump.
What information do I need when choosing a submersible pump?
Before choosing a submersible pump, identify:
- The water source.
- The type of water being pumped.
- The required flow rate.
- The vertical head height.
- The horizontal distance.
- The pipe diameter.
- Whether the pump will supply a tank, house, irrigation system or discharge point.
These details help determine which pump can meet the required duty.
What size submersible pump do I need?
Choosing a submersible pump involves more than selecting a particular motor size.
The right pump depends on:
- The application
- Head height
- Distance
- Pipe size
- Required flow rate
- Water source
- Type of water being pumped
Not sure which pump meets your requirements? Contact our team before ordering: How many litres per minute should my submersible pump deliver?
The required flow rate depends on how the water will be used and how much water is needed at one time. Head height, pipe length, pipe diameter and system resistance all affect the flow a pump can deliver.
Calculate the required litres per minute for the application, then select a pump that can provide that flow at the system's total head.
Pump Types and Applications
Submersible Pump vs Jet Pump: Which Do You Need?
A submersible pump operates fully submerged in water. Depending on the model, it can be used for household supply, rainwater, dirty water, stormwater, grey water, sewage, effluent, irrigation or transfer.
A jet pump sits above ground and can draw from above-ground or below-ground water sources. Jet pumps are commonly used for household water supply, gardens, irrigation and water transfer.
The right choice depends on your water source and how the pump will be used.
Dirty-water pump vs clean-water pump: what’s the difference?
Not every submersible pump can handle the same type of water.
Some pumps are designed for clean water with little or no debris.
Others can handle dirty water, stormwater, grey water, sewage or effluent.
Different pumps use different impellers, including vortex, grinder and cutter or macerator impellers.
Choosing the right pump starts with understanding what you need to pump.
Explore submersible pumps for different applications
Can one submersible pump handle clean water, dirty water and sewage?
No. Submersible pumps are designed for specific water types and solids-handling requirements. A clean-water pump may block or become damaged if used for dirty water or sewage. Sewage and septic applications may require vortex, cutter, macerator or grinder pumps.
Choose a pump that is specifically rated for the water and solids it will handle.
Installation and Pump Controls
What is the difference between a float switch and a pressure switch?
A float switch turns a submersible pump on and off as the water level rises and falls. External float switches hang beside the pump, while internal or attached float switches are useful in smaller sumps and confined spaces.
Some high-head submersible pumps can operate with a pressure switch or automatic pressure controller, making them suitable for household supply or light irrigation.
Explore submersible pumps with different float options
Does a submersible pump need a check valve?
A check valve may be required to prevent water draining back through the pump when it switches off. This helps prevent the impeller from spinning backwards and reduces reverse flow through the system.
Swing or ball check valves may suit some submersible installations. A spring check valve may not suit a low-head pump because it requires enough pressure to open. Follow the pump manufacturer's instructions or seek advice for the specific installation.
Can a submersible pump sit on the bottom of a tank?
It can, but it is better to elevate the pump slightly above the bottom of the tank.
Sediment and debris settle at the bottom. Raising or suspending the pump can help prevent blockages and reduce the amount of sediment entering it.
A small change in positioning can make a big difference.
How do I stop sediment clogging a submersible pump?
Keep the pump intake away from sediment at the bottom of the tank. Elevate the pump slightly above the base or suspend it higher in the water so settled debris is less likely to enter the intake.
The correct position depends on the tank, pump design, water level and manufacturer's requirements.
Troubleshooting a Submersible Pump
Why does my submersible pump keep tripping the power?
A submersible pump may trip the power because of:
- An electrical fault within the pump
- A blockage
- Water entering sealed electrical components
- A problem with the alarm or control box
The fault could be inside the pump or elsewhere in the system.
Turn the pump off and have the cause checked before attempting to run it again.
Why is my submersible pump humming but not pumping?
If your submersible pump is humming but no water is moving, there may be a blockage or something caught around the impeller.
A humming noise can also occur when the capacitor has failed or needs replacing. Switch the pump off rather than leaving it running, as this could cause further damage.
Why did my submersible pump fail after running dry?
Submersible pumps are designed to operate while submerged in water.
If a pump runs dry, it can overheat and damage its internal components, potentially causing the pump to fail.
Protecting your pump from running dry can help prevent unnecessary damage and replacement costs.
Why is my submersible pump delivering less water than expected?
Reduced flow may be caused by a blocked intake or impeller, sediment, restricted pipework, excessive head, an undersized pipe, low water level, wear or a pump that is not correctly sized for the system.
Check the intake and pipework, then compare the required flow and total head with the pump's performance curve.
When should I replace rather than repair a submersible pump?
The decision depends on the cause of the failure, pump age, availability of parts and the cost of repair compared with replacement. A blockage, capacitor or control problem may be repairable, while serious motor damage or repeated failures may make replacement more practical.
Have the pump diagnosed before assuming it needs replacing.
Need Help Choosing or Troubleshooting a Submersible Pump?
Provide the water source, water type, required flow rate, head height, distance, pipe size and details of the problem. Pumps Online can use this information to help identify a suitable pump or the next troubleshooting step.