Choosing a pressure pump for your house
A pressure pump is only as good as its switch and its vessel. The motor is the least interesting part.
If your house runs off a tank, a bore or weak mains pressure, a pressure pump is what makes the shower feel normal. Look at how it controls pressure, not how big the motor is. That is where cheap units fall down.
What a pressure pump actually does
It senses a drop in pressure when you open a tap, starts, and stops once pressure is back. A pressure vessel holds a cushion of water so the pump does not start for every cup you fill. Without a healthy vessel, the pump cycles constantly.
Switch or controller?
Older pumps use a simple pressure switch. Many newer ones use an electronic controller that senses flow and also protects against running dry. Neither is wrong, but they behave differently.
| Question | Pressure switch | Electronic controller |
|---|---|---|
| Start and stop | By pressure only | By flow and pressure |
| Dry-run protection | Usually separate | Often built in |
| Pressure steadiness | Rises and falls between cut-in and cut-out | Steadier |
| Repair | Simple, cheap parts | Often replace the controller |
Size on flow, then check the pressure
Add up what you run at once: a shower and a washing machine, say. That is your flow. Then ask for the pump curve to see what pressure it holds at that flow. A pump rated for high pressure at no flow may sag badly when two things run together.
Bigger is not better here. A pump much stronger than the pipework can hammer fittings and short-cycle. Match it to the house.
Why house pressure pumps give trouble
Cycling on and off. The vessel has lost its air charge, or a tap or toilet valve is leaking slightly. A leaking toilet inlet is a very common cause.
Hammering. A banging noise when taps close points to pressure spikes, a failing vessel or loose pipework.
Weak flow. Check the strainer and the supply to the pump before blaming the motor.
A pump fed from a tank also suffers when the tank runs low. For tank-side choices, see choosing a water tank pump.
Questions to answer before you buy a house pressure pump
These questions narrow the choice before you look at a single model.
- What is the water source? A tank, a bore and weak mains pressure each put different demands on the pump.
- What runs at once? A shower and a washing machine together set your flow. Size the pump on that.
- What pressure does the pump hold at that flow? Ask for the pump curve, not just the maximum rating.
- Switch or controller? A controller gives steadier pressure and often built-in dry-run protection. A switch has simpler, cheaper parts.
- Is there a pressure vessel, and can you check it? A healthy vessel stops the pump starting for every cup of water.
- Who will install it? The plumbing connection is licensed work, and the wiring needs a licensed electrician.
Pressure pump symptoms and the first thing to check
| Symptom | Likely cause | Check first |
|---|---|---|
| Pump keeps starting and stopping | Vessel lost its air charge, or a small leak | Toilet inlets and taps; a leaking toilet inlet is a very common cause |
| Banging when taps close | Pressure spikes, a failing vessel or loose pipework | Pipe clips and the vessel |
| Weak flow | Blocked strainer or poor supply to the pump | Strainer and the supply before blaming the motor |
| Pressure rises and falls | Normal for a pressure switch | Ask about a controller if it bothers you |
| Sagging pressure with two taps open | Pump too small for the flow | The pump curve at your flow |
If the pump draws from a tank, the tank level matters too. See rainwater tank pump not working for the tank-side checks.
Frequently asked questions
What does a house pressure pump do?
It boosts and holds water pressure to your taps, using a pressure switch or controller and a pressure vessel to avoid constant starting.
Why does my pressure pump keep turning on and off?
Often the pressure vessel has lost its air charge, or a tap or toilet valve is leaking slightly so pressure keeps dropping.
Should I buy the most powerful pump?
No. An oversized pump can hammer fittings and short-cycle. Size it on the flow you use at once, and check the pump curve.
Can I install a pressure pump myself?
Not the plumbing connection or backflow protection, which are licensed work. The wiring needs a licensed electrician.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- NHMRC. Australian Drinking Water Guidelines
- Australian Building Codes Board. National Construction Code — Volume Three (Plumbing Code of Australia)