Buying a pump sounds easy enough.
You need to move a liquid from A to B. Find a pump, click buy and job done.
Except… not quite.
There are hundreds of different pumps designed for different applications, liquids, flow rates and installation conditions. Pick the wrong one, and you could end up with a pump that doesn’t deliver enough water, doesn’t produce enough pressure or simply isn’t designed for its intended purpose.
The good news is that choosing the right pump doesn’t have to be complicated.
Before you start comparing prices and specifications, there are a few key questions to answer.
What are you actually pumping?
First things first: what liquid needs moving?
This might sound obvious, but it’s one of the most important things to consider.
Clean water, dirty water, rainwater, sewage and other liquids can all require completely different types of pumps.
For example, a clean water pump may be perfectly happy moving water from a tank or well, but it isn’t necessarily designed to handle solids, debris or wastewater.
If you’re draining a flooded area, emptying a pit or moving dirty water, you’ll generally need a drainage or dirty water pump designed to cope with the conditions.
For sewage and heavily contaminated water, you’ll need a pump specifically designed for that application, often with features such as larger free passages to allow solids to pass through.
The rule is simple: don’t just ask how much water you need to move. Ask what is in the water too.
How much liquid do you need to move?
This is where flow rate comes in.
Flow rate tells you how much liquid a pump can move over a given period, commonly measured in litres per minute (L/min), litres per second (L/s) or cubic metres per hour (m³/h).
If you’re draining a large area, for example, you may need a much higher flow rate than someone simply transferring water between two domestic tanks.
But bigger isn’t automatically better.
A pump capable of moving huge volumes of water isn’t necessarily the right choice for a smaller application. It could use more energy than necessary or operate outside its ideal range.
Think about what you actually need the pump to achieve, rather than simply choosing the pump with the biggest number.
How far does the water need to travel?
Flow rate is only half the story.
You also need to consider head – essentially, the amount of pressure or lift the pump needs to overcome.
If you’re moving water uphill, the vertical height between the water source and the discharge point matters.
But it’s not just vertical distance.
Pipe length, pipe diameter, bends, valves, filters, and other restrictions in the system can all create resistance. The pump needs to overcome these losses while still delivering the required flow.
For example, a pump might be advertised as capable of producing a certain maximum head, but that doesn’t necessarily mean it will deliver your required flow rate at that height.
That’s why looking at a pump’s performance curve is important when selecting a pump for anything beyond a straightforward application.
Submersible or surface pump?
Another big question: where is the pump going to sit?
Submersible pumps are designed to operate while submerged in the liquid they’re pumping. They’re commonly used for drainage, wastewater, tanks, pits and other applications where the pump needs to sit directly in the water.
Surface pumps, on the other hand, are installed outside the liquid and draw liquid through pipework.
Neither option is automatically better. It depends on the application.
A submersible pump can be a straightforward choice when you’re draining a flooded area or tank, while a surface pump may be more suitable where the pump needs to remain accessible and dry.
Do you need a self-priming pump?
If you’re using a surface-mounted pump, priming is another consideration.
Some pumps need to be manually primed before operation, while self-priming pumps are designed to remove air from the suction pipe and establish pumping automatically, within the manufacturer’s specified conditions.
This can be particularly useful in applications where the pump may regularly lose prime or where ease of operation is important.
However, “self-priming” doesn’t mean “will pump anything from anywhere.”
There are still limits around suction lift, pipework, liquid conditions and the manufacturer’s operating requirements.
What size are the connections?
It’s easy to overlook the physical side of choosing a pump.
Before buying, check the inlet and outlet connection sizes and types. You’ll also need to consider the existing pipework and whether adapters or additional fittings will be required.
A pump can have all the right performance specifications and still cause headaches if it doesn’t connect properly to your existing system.
Check the details before ordering rather than discovering you’ve got the perfect pump… and absolutely no way of connecting it.
How often will the pump be used?
There’s a big difference between a pump that runs occasionally and one that’s expected to operate continuously.
Consider how frequently the pump will run, how long it will operate for and whether the application is temporary or permanent.
A pump used for occasional drainage doesn’t necessarily need the same specification as one operating for hours every day.
Duty cycle, motor rating, cooling method and the overall construction of the pump can all become important depending on the application.
If you’re unsure, it’s worth getting advice before making a decision.
Don’t forget the liquid temperature and conditions
Water isn’t always just water.
Temperature can affect which pump is suitable, while abrasive particles, chemicals or other contaminants can affect the materials and components required.
If you’re pumping anything other than clean water, make sure you provide as much information as possible about the liquid.
What is it? What’s the temperature? Does it contain solids? Is it abrasive or chemically aggressive?
The more information you can provide, the easier it is to identify a suitable pump.
Still not sure which pump is right?
That’s exactly what PSD is here for.
We stock a wide range of pumps, spares and accessories for different applications, from drainage and dirty water through to clean water, boosting, irrigation and more.
If you know exactly what you need, you can browse our range and get straight to it. If you’re staring at a list of specifications and wondering what on earth half of them mean, we’re happy to help point you in the right direction.
