Narrow it down
One tap or every tap?
If only one tap or shower is weak, the problem is most likely at that fitting.
Hot, cold or both?
Weak hot water with strong cold points to the hot water system or the valves on it.
Sudden or slow?
A sudden drop suggests a leak, a burst or a valve. A slow decline over years suggests pipes clogging inside, or a valve wearing out.
Ask the neighbours
If they've lost pressure too, ring your water company: there may be works or a fault in the street.
Check the stop tap
Make sure the stop tap at your meter is fully open. It's easy to leave it half closed after a repair.
What the pattern usually means
| Likely cause | Who to call | |
|---|---|---|
| One tap or shower weak | A blocked aerator or shower head, or a worn tap cartridge | Try cleaning it first, then a plumber |
| Hot water weak everywhere | A valve on the hot water system, a tempering valve or a blocked inlet | A hot water specialist: see tempering valves |
| Whole house, sudden drop | A leak or burst, a part-closed valve, or a problem in the street | Check the meter, then your water company or a plumber |
| Whole house, worse over years | Old pipe clogged inside, or a failing pressure reducing valve | A plumber |
| Pressure too high | No pressure reducing valve, or one that has failed | A plumber |
Signs the pressure is too high
- Pipes bang or shudder when taps close: see water hammer.
- Taps spray hard when you open them only a little.
- The hot water relief valve drips more than it used to.
- Washers, cistern valves and flexible hoses wear out early.
What a plumber will do
A plumber will measure the pressure with a gauge at the meter and at the weak fitting, which shows straight away whether the supply or your pipes are the problem. From there they might clean or replace a blocked part, fix a leak, replace a run of corroded pipe, or fit or replace a pressure reducing valve.
Where your water comes from a tank, weak pressure is often down to the pump: see tank pumps.
What changes the job
Finding the cause is most of the work. A blocked aerator takes minutes; old galvanised pipe that has narrowed inside may mean replacing whole runs, and a pipe under a slab is harder to reach than one under a timber floor. If the supply in the street is the problem, that's for your water company, not a plumber.
What you can try first
You can
- Unscrew a tap aerator or shower head and rinse out the grit.
- Check the stop tap at the meter is fully open.
- Change a whole-house filter cartridge if you have one and you're in Queensland or WA, where the homeowner lists include it.
- Ask your water company whether there's work or a fault in your street.
Leave to a licensed plumber
- Fitting, adjusting or replacing a pressure reducing valve.
- Replacing corroded or narrowed pipe.
- Valves on the hot water system, and tempering valves.
- Fitting or connecting a pump.
Rules that apply
In WA and Queensland, the regulators publish lists of small jobs you may do yourself. WA's list covers maintaining, repairing or replacing a shower head, repairing a tap other than a thermostatic mixing tap, replacing a cistern washer and replacing a water filter cartridge; all other water supply plumbing "must be carried out by a licensed plumber or permit-holder." The QBCC guide's list for Queensland includes "replacing a shower head or domestic water filter cartridge".
For the other states, see what you can do yourself, and check any plumber's licence on your state's register before the work starts.
Questions to ask the plumber
- What's the pressure at the meter, and at this tap?
- Is the problem in my pipes or in the supply?
- Do I need a pressure reducing valve, or is mine failing?
- Would replacing one section fix it, or does the whole run need doing?
What we would do
Start at the weak tap: a clogged aerator or shower head is a common cause of one poor flow, and it's a five-minute check. If the whole house is weak or the pipes bang, get a plumber to put a gauge on it before anyone sells you a pump or a new valve. Measuring first means you fix the real cause, and a plumber who specialises in pressure and pipe problems will start there.