How to compare pressure pumps: what actually matters

Start with the duty point, not the maximum

Max flow and max head never happen together. Max head is what the pump reaches at zero flow, with the tap shut. Max flow is what it delivers at almost no pressure. Neither is how you use it.

What matters is the middle: how much pressure the pump still holds at the flow you draw. Two showers and a tap is roughly 25 to 30 litres a minute. Ask for the pump curve, find that flow, and read the head across. A pump quoting a big maximum can sit below a modest one at the flow you care about.

If a seller can’t produce a curve, that in itself is an answer.

How the pump decides to run

This is the biggest split in the market and it’s rarely explained.

A traditional pump uses a mechanical pressure switch: pressure drops to a set point, contacts close, the motor runs flat out, pressure builds, contacts open. It only has two states, off and full speed. That means it starts and stops constantly through a shower, uses full power whether you’re filling a bath or rinsing a cup, and everything wears at that rate. The switch itself is a moving contact under load. They stick, they pit, and a switch that jams closed runs the pump against a shut tap.

An electronic pressure switch, often sold as a pump controller, does much the same job with less to go wrong. It senses pressure and flow electronically instead of through a contact carrying the motor current, so there is no mechanism to pit or stick, and it usually brings dry-run protection with it. Some versions also delay the restart or hold a small reserve to cut down on short cycling. What it does not change is the motor. The pump still runs at one speed, so the energy used for a small draw, and the wear from starting flat out every time, stay where they were.

A variable-speed pump reads pressure continuously and changes motor speed to hold it. It runs slower for small draws, holds pressure steady instead of sawing between two set points, and starts and stops far less often. Quieter, less energy for the same water, less wear.

Worth asking whichever of the three you are looking at: can you set the pressure it holds, and the pressure at which it stops? Fixed factory settings are fine until your house doesn’t match them.

The motor itself

Most pumps use an induction motor. A permanent-magnet motor uses magnets in the rotor rather than inducing current in it, so less energy is lost as heat. In practice that means meaningfully better efficiency, and it is also what makes fine speed control possible. The two go together.

Ask about winding insulation class as well. It sounds obscure, but it’s the thermal headroom the motor has before the windings degrade. Class F tolerates more heat than Class B, which matters on hot days, long runs and undersized installations. It’s a number that only appears on datasheets of people who are proud of it.

What the water touches

Two pumps can look identical and have completely different wet ends.

Impellers are commonly plastic (often PPO) or stainless steel. Plastic is fine in clean water and cheaper to make. Stainless handles grit, silt and years of duty better, which is the normal condition for tank water. Casing and fittings are the same question: stainless resists corrosion where coated steel or brass eventually doesn’t, and the fittings are what you’ll be undoing in ten years if something needs replacing.

Ask what the impeller, the pump casing and the inlet and outlet connections are each made from. They are often three different answers.

What it does when something goes wrong

Pumps mostly fail in predictable ways, and good ones expect it.

Dry running is the big one: a tank runs empty or a valve is shut, and the pump keeps going with nothing to cool it. Seals go quickly. Ask whether it detects that, stops, and then restarts by itself when water returns, or whether someone has to go out and reset it. That last part matters more than it sounds.

Then ask about over-current and over-temperature protection, and whether the pump self-primes or has to be primed by hand each time air gets in. Self-priming is one of those features you never think about until you’re lying on wet ground with a jug.

Noise, and why the number usually means nothing

A decibel figure without conditions is marketing. Measured at what distance, at what flow, at what pressure? A pump is much louder working hard than idling, and 1 metre versus 3 metres is a large difference on its own.

If you’re comparing noise, ask for the distance and the operating point, and treat any figure without them as unquoted. In practice, a pump that runs slower for small draws and starts less often is quieter in a house than the datasheet difference suggests.

Connectivity: useful, and a dependency

App connection helps most with the things that are otherwise invisible: pressure over time, whether the pump ran overnight when nobody was home, a fault you would otherwise discover in the shower.

It is also another thing that can break, and it needs a network where the pump lives, which is often a shed or a pump housing at the edge of the WiFi. Ask whether the pump still works normally with the app removed or the internet down. It should. If connectivity is load-bearing rather than additive, that’s a fair reason to walk away.

Approvals, and who stands behind them

Electrical approval is not optional. In Australia a pump should carry the RCM mark and be registered by a responsible supplier, meaning that supplier takes legal responsibility for it complying. Ask which approvals a pump holds rather than accepting a general claim of being certified, and be wary of listings that show marks without saying who holds them.

Water-contact approvals are worth asking about too, and the answer varies by product type and by what the pump connects to. It’s a fair question to put to any seller, and a straight answer is a good sign.

Warranty, and what it’s worth

Length is the headline. The useful questions sit underneath it.

Who honours it, an Australian entity or an overseas factory via a reseller? What’s covered, and specifically is the motor covered for the same period as the rest? Is a failed seal from dry running excluded, given that’s a common failure? And what happens in practice: replacement, repair, or a parts-only claim where you pay a plumber twice.

Ask about spare parts while you’re there. A pump you can get a seal kit for in five years is worth more than a slightly cheaper one you replace entirely.

When simpler is the right answer

None of this means the most sophisticated pump wins every time.

If you want to run a single garden tap off a tank a few times a week, a basic constant-speed pump is cheaper, has fewer things in it, and any plumber can work on it. The case for variable speed, protections and app connection gets stronger the more the pump runs, and the more it matters that it doesn’t stop. A whole house, a family, a pump you would rather not think about.

Common questions

Is a higher wattage pump better?

Not by itself. Wattage is what the pump consumes, not what it delivers. A more efficient motor can produce the same pressure and flow for less power, so comparing wattage alone can lead you to the worse pump.

What flow rate do I need?

Roughly 25 to 30 litres a minute covers two showers and a tap in a typical home. Bigger homes, multiple bathrooms running at once, or long pipe runs push it higher. Work out the flow first, then compare the pressure each pump holds at that flow.

Does variable speed really save much energy?

It depends how much you use it. The saving comes from running slower for small draws instead of full speed for everything, so households that use water often see more benefit than an occasional garden tap.

Is a stainless impeller worth paying for?

In clean water a plastic impeller lasts well. In tank water carrying a little silt or grit, stainless holds its shape and clearances longer. If the pump is on tank supply, it is worth asking about.

What should I ask a seller for?

The pump curve, the impeller and casing materials, what protections it has, which approvals it holds and who registered them, and what the warranty covers and who honours it. If those answers are hard to get, that tells you something.