Low water pressure, high pressure or banging pipes?

Low pressure: check the supply first

1. Check Water Corporation’s outages and works page. Works on a main nearby can drop the pressure for the whole street.
2. Work out whether it’s every tap or just one, and whether it’s hot, cold or both. That tells you where to look next.
3. Do Water Corporation’s flow test. Turn off every tap and water-using appliance, and write down the black and red numbers on the meter. Then run the front garden tap for 60 seconds (catch the water for the garden) and read the meter again. The difference is how much came out in a minute.
4. Keep in mind that the flow at a tap is always lower than at the meter. Water Corporation’s 20-litres-a-minute aim is measured at the meter outlet, not at your shower.
5. If the result looks poor, you can ask Water Corporation for a pressure and flow test at the meter through their website, or ring 13 13 75.

When the supply is fine but the house isn’t

If the street supply checks out, the restriction is in the property plumbing, which is the owner’s side of the meter. The usual suspects:

• One tap or shower only: a blocked aerator or shower head, a worn mixer cartridge, or an isolation valve under the basin that’s been left half closed.
• Hot water only: something in or around the hot water system, such as a tempering valve, an inlet strainer or a valve on the unit. Our no hot water page goes through the checks by system type.
• The whole house: a main stop tap that isn’t fully open, a pressure limiting valve that has failed and is restricting flow, or old galvanised pipe that has rusted up inside. That last one is common in older homes that still have their original supply line.
• Pressure dropping for no obvious reason, together with a meter that keeps moving when everything is off, points to a leak. Start with our leak detection page.

High pressure: why Perth homes need a pressure limiting valve

Under its licence, Water Corporation’s standard range for the Perth metro area is 15 to 100 metres head at the meter. One hundred metres head works out at nearly 1,000 kPa, about double the 500 kPa limit for outlets inside a home. Water Corporation says the pressure you get depends on how high the reservoir or water tower is above your property. Homes lower on a hill, or below a reservoir, can get high pressure.

Water Corporation also says high pressure can mean more leaks and bursts, shorter-lived appliances and fixtures, and noisy pipes. A pressure limiting valve, usually fitted on the house side of the meter, brings the house supply back under the limit. Like any valve, it wears out, and when it fails it can let full mains pressure through or choke the flow.

Some properties get water pressure outside the standard range. Water Corporation flags this with a message on the bill and a notification on the Landgate Property Interest Report, so it’s worth looking for if you’re buying.

Water hammer: the bang when a tap shuts

That thump or knock in the wall when a tap snaps shut, or when the washing machine or dishwasher finishes filling, is water hammer. Water moving through the pipe is stopped suddenly by a fast-closing valve, and the shock travels back along the pipe. It gets worse when the pressure is high and when pipes aren’t clipped firmly in the wall or roof space.

The fix starts with a pressure test, because high pressure is often what’s behind it. After that, the options are a pressure limiting valve if there isn’t one or the old one has failed, re-securing loose pipework, and a water hammer arrestor near the appliance or valve that sets it off. Don’t ignore it. Repeated shocks are hard on joints, flexi hoses and appliance valves.

What we do

We put a gauge on the supply and measure the static pressure, then check the stop tap and any pressure limiting valve and track down where the flow is being lost or where the hammer starts. You’ll get a straight answer on what’s causing it. If the problem turns out to be the supply at the meter, that’s for Water Corporation to test and sort out, and we’ll tell you so rather than charge you to keep looking inside.

Common questions

What is normal water pressure in Perth?

Water Corporation supplies the Perth metro area within a standard range of 15 to 100 metres head, measured at the meter, and aims for at least 20 litres a minute. Inside the house, the plumbing standard caps static pressure at outlets at 500 kPa, about 50 metres head.

Why has my water pressure suddenly dropped?

Check Water Corporation’s outages and works page first. If nothing is listed, likely causes are a partly closed stop tap, a failing pressure limiting valve, a blocked aerator or shower head, or a leak. If the meter keeps moving with everything turned off, treat it as a leak.

Do I need a pressure limiting valve?

If the static pressure at your meter is over 500 kPa, the pressure at outlets inside the house has to be brought under that limit, and a pressure limiting valve is the usual way to do it. A plumber can measure it with a gauge in a few minutes.

What causes pipes to bang when a tap turns off?

Water hammer. A fast-closing valve stops the water suddenly and the shock runs back through the pipe. High pressure and loose pipe clips make it worse. Fixes include lowering the pressure, securing the pipes and fitting a water hammer arrestor.

Is low pressure Water Corporation’s problem or mine?

Up to the meter it’s Water Corporation’s, and you can ask them for a pressure and flow test at the meter. From the meter into the house it’s the property owner’s plumbing, and a licensed plumber needs to find and fix the restriction.

Related pages

• Burst pipe: what to do
• Leak detection Perth
• Hot water system leaking
• No hot water? Hot water repairs
• Emergency plumber Perth
• Get a quote