The shower is running normally.
Then someone turns on the kitchen tap.
Suddenly the shower loses pressure.
Or the washing machine starts filling and the water from the bathroom tap slows noticeably.
A small change can be normal because several fixtures are sharing the water available to the house.
A dramatic change is different.
If using one tap regularly causes another part of the house to lose a significant amount of flow, there may be more going on.
Pressure and Flow Aren’t Quite the Same Thing
People usually describe the problem as “low water pressure”.
Sometimes the real issue is water flow.
Pressure describes the force pushing the water through the plumbing system.
Flow describes how much water is actually moving through it.
A plumbing system can appear perfectly adequate when only one fixture is operating.
Open several fixtures at once and a restriction somewhere in the system becomes much more obvious.
Think of it like traffic.
One car can move through a narrow road without a problem.
Send twenty cars through at once and suddenly the bottleneck matters.
Start With the Simplest Question: Is It the Whole House?
Try several fixtures.
Does the problem occur everywhere?
Or does it only affect one shower or tap?
If only one fixture has poor performance, the problem may be local to that fixture.
Possible causes include:
- a clogged aerator
- a restricted shower head
- a faulty tap or mixer
- debris within the fitting
- an issue with the pipe supplying that fixture
If several parts of the house are affected at the same time, it is worth looking further upstream.
Check Whether the Stop Valve Is Fully Open
The property’s stop valve controls the drinking water entering the property.
Urban Utilities recommends checking that it is fully open when investigating low water pressure or flow.
A partially closed valve can restrict the amount of water available to the entire house.
With one tap running, you might barely notice.
Once several fixtures demand water at the same time, the restriction becomes much more obvious.
What About the Pressure Reduction Valve?
Many newer homes have a pressure reduction valve, sometimes called a pressure limiting valve, installed to help protect internal plumbing and appliances from excessive pressure.
Urban Utilities notes that these are common on properties built after 2005.
If the valve has been adjusted, damaged or is no longer operating correctly, it may affect the way water is supplied through the house.
This is something worth having inspected rather than simply adjusting components at random.
A Leak Can Also Reduce Available Flow
Not every leak announces itself with water pouring through a ceiling.
A leak somewhere in the plumbing system can reduce the amount of water reaching the fixtures where you actually want it.
Look for things such as:
- unexplained increases in water usage
- damp ground
- wet areas beside the house
- water meter movement when everything is turned off
- moisture marks
- sounds of running water
RJT Plumbing & Gas can investigate suspected leaks and use professional leak-detection methods where appropriate.
Older Plumbing Can Create Restrictions
The internal condition and size of the plumbing also matter.
Older pipework can develop restrictions.
Previous renovations may have created unusual pipe layouts.
Extensions may have added additional fixtures to plumbing that was originally designed for a smaller house.
Sometimes the problem is not one failed component.
It is the combined effect of the plumbing system trying to serve more demand than it once did.
Does Hot Water Pressure Drop More Than Cold?
This is another useful clue.
If cold-water performance is reasonable but hot-water flow is consistently poor, the problem may relate specifically to the hot-water side of the system.
The hot-water unit, valves, pipework or other components may need investigation.
That is different from a house where both hot and cold water lose flow under demand.
What If It Only Happens at Peak Times?
It is worth noting when the problem occurs.
Does it happen every time two fixtures are used?
Only occasionally?
Only on hot water?
Only in one bathroom?
Only when the washing machine fills?
Small details can help narrow down where the restriction is likely occurring.
Should Every Tap Run at Full Flow at the Same Time?
Not necessarily.
Opening several fixtures places greater demand on the plumbing system and some reduction can occur.
The question is whether the change is reasonable.
If turning on one ordinary household fixture makes another almost unusable, it is worth finding out why.
You should not have to schedule showers around whether somebody is washing the dishes.
Get the Cause Checked Rather Than Guessing
Low water pressure is not one problem with one solution.
The issue could be at a fixture, valve, hot-water system, internal pipework or elsewhere within the property’s plumbing.
That is why diagnosing the cause matters.
RJT Plumbing & Gas services North Lakes, Mango Hill, Griffin, Kallangur, Murrumba Downs and surrounding areas across Moreton Bay and Brisbane’s northside.
If the shower disappears every time someone turns on another tap, get in touch and let the team work out where the water is really being held back.
Frequently Asked Questions
Why does my shower pressure drop when another tap is opened?
Multiple fixtures share the water available through the plumbing system. A large drop can indicate a restriction, valve issue, leak, fixture problem or limitation within the internal plumbing.
Can a pressure reduction valve cause low water pressure?
A pressure reduction valve forms part of the property's pressure-control system. An issue with the valve or its setting can contribute to poor water-flow performance and should be properly inspected.
Can a hidden leak reduce water pressure?
A leak can reduce the amount of water available to fixtures. Other signs can include unexpected water usage, damp areas or meter movement when no water should be running.
Why is only my hot-water pressure low?
If cold flow is normal but hot flow is poor, the issue may be associated with the hot-water system, valves or hot-water pipework.
