Low water pressure in one tap is usually a blocked aerator or failing tap part. Low pressure through the whole house points to a partly closed valve, a leak, a failing pressure limiting valve or old pipes. Water hammer, the bang when a tap shuts, comes from pressure that’s too high or pipes not secured. A plumber can test it in minutes.
One tap or the whole house?
Start by working out how widespread the problem is. Turn on several taps and the shower, one at a time and then together.
- One tap or shower is weak: the problem is at that fixture.
- All hot taps are weak, cold is fine: the problem is on the hot water side, such as the hot water system, its valves or a tempering valve.
- Everything is weak: the problem is on the supply to the house.
Causes of low pressure
| Cause | Clue | Fix |
|---|---|---|
| Blocked tap aerator | One tap sprays unevenly or weakly | Unscrew and clean the aerator |
| Clogged showerhead | Weak or uneven spray from one shower | Clean or replace the showerhead |
| Partly closed isolation valve or meter valve | Pressure dropped after recent work | Open the valve fully |
| Hidden leak | Meter moves when all water is off | Find and repair the leak |
| Failing pressure limiting valve | Whole house weak, valve is old | Replace the valve |
| Corroded galvanised pipes | Older home, rusty water, gradually worsening | Replace the pipework |
| Street supply issue | Neighbours affected too | Contact Unitywater |
If you suspect a leak, our guide on how to find a water leak explains the meter test.
What is water hammer?
Water hammer is the bang, thud or shudder you hear in the pipes when a tap, washing machine or dishwasher shuts off quickly. Water moving through a pipe has momentum. When a valve slams shut, that moving water stops suddenly and sends a pressure wave back through the pipe, which bangs against fittings and bends.
It’s made worse by:
- high water pressure
- quick-closing valves in appliances and mixer taps
- pipes that aren’t properly clipped, so they move and knock against the frame
It’s not just noise. Each spike puts stress on joints, valves, flexi hoses and appliance hoses, and over time can cause leaks.
Need a local plumber?
Morrisons Maintenance Plumbing has served Caloundra to Maroochydore for 14+ years. Book a plumber or call 1300 149 288.
The 500 kPa guideline
The Australian plumbing standard AS/NZS 3500.1 sets a maximum static water pressure of 500 kPa at outlets inside a building, other than fire services. Mains pressure in some streets is higher than that, especially in lower-lying areas. When it is, a pressure limiting valve is used to bring it down.
A plumber can screw a pressure gauge onto an outside tap and read the static pressure in a few seconds.
Pressure limiting valves
A pressure limiting valve (PLV) is fitted on the water supply, usually near the meter, and reduces mains pressure to a safe level for the house. It:
- protects taps, the hot water system, appliances and flexi hoses
- reduces water hammer
- can stop a hot water relief valve from dripping constantly
Like any valve, a PLV wears out. When it fails, pressure can drop too low, or it can let full mains pressure through. If your pressure has changed noticeably and your PLV is many years old, it’s worth having it tested.
Quick checks you can do
- Check the meter valve is fully open. It’s at the water meter, usually near the front boundary.
- Clean the aerators on weak taps. Unscrew the tip of the spout and rinse out the screen.
- Soak the showerhead in vinegar to dissolve mineral build-up.
- Do the meter test to rule out a leak.
- Ask the neighbours whether their pressure has dropped too.
If those don’t solve it, or you have banging pipes, a plumber can test the pressure, check the PLV and secure loose pipes. See our plumbing services or book a pressure check.
Frequently asked questions
Why is my water pressure suddenly low?
Check whether it’s one tap or the whole house. One tap often means a blocked aerator or worn part. Throughout the house, it can be a partly closed valve at the meter, a hidden leak, a failing pressure limiting valve or a supply issue in the street.
What causes water hammer?
Water hammer happens when fast-moving water is stopped suddenly, such as when a tap or appliance valve shuts. The shockwave bangs through the pipes. High water pressure and pipes that aren’t properly secured make it worse.
Is water hammer dangerous?
It can damage your plumbing over time. Repeated pressure spikes strain joints, valves, flexi hoses and appliances, which can lead to leaks. It’s worth having a plumber check the pressure and fix the cause.
What is a pressure limiting valve?
A pressure limiting valve is fitted near the water meter to reduce mains pressure to a safe level for the house. It protects taps, hot water systems and appliances, and can reduce water hammer.
What is the maximum water pressure for a house in Australia?
The plumbing standard AS/NZS 3500.1 sets a maximum static pressure of 500 kPa at outlets inside a building, except fire services. If your mains pressure is higher, a pressure limiting valve is used to bring it down.
Honest, upfront pricing from a local, family-owned plumber.
Call 1300 149 288 or request a quote. QBCC licence 1296541.