26th July 2026
A water leak is not always easy to see.
Sometimes there is no water pooling, no obvious dripping tap and no damp patch inside the home. The first sign may be an unexpectedly high water bill—or a water meter that continues moving when nobody is using water.
Precision Pipes is currently investigating a suspected underground water leak at an older property in Pymble. After the plumbing inside the house was isolated, the water meter continued registering water flow. This indicated that water was likely escaping somewhere along the underground water service running between the meter and the house.
Water Meter Continuing to Run During Pymble Leak Test
The meter continued registering water flow after the house plumbing was isolated, indicating a likely leak along the underground water service.
What first indicated there may be a water leak?
At this Pymble property, one of the clearest warning signs was the water meter moving rapidly when no water was intentionally being used.
A water meter records the water passing into a property. Therefore, if all taps, toilets, appliances and irrigation systems are off but the meter continues moving, water is still flowing somewhere.
However, the meter alone does not tell us exactly where the leak is located.
The water could be escaping from:
A running toilet cistern
A leaking shower, bath or basin tap
A kitchen or laundry tap
An outdoor tap
A hot-water system
A washing machine or dishwasher connection
An irrigation system
Concealed plumbing inside the building
The underground water pipe between the meter and the house
Sydney Water recommends turning off all water-using taps and appliances, recording the meter reading, avoiding water use for at least one hour and then checking whether the reading has changed.
Why can water leaks be more common in older properties?
Water leaks can occur in homes of any age, but older properties may be more vulnerable because their pipework, valves, joints and plumbing fixtures have been in service for many years.
Possible causes include:
Corrosion or deterioration of older pipes
Failed pipe fittings or joints
Natural ground movement
Accidental damage to underground pipework
Excessive pressure within the water service
Worn toilet inlet or outlet valves
Deteriorated tap washers, cartridges or O-rings
Ageing flexible hoses and appliance connections
Previous repairs or alterations that have started leaking
A small internal leak may appear insignificant, but a toilet that continually runs or a pipe that leaks around the clock can waste a substantial amount of water. Sydney Water advises homeowners to check taps, toilets, hot-water expansion valves and connected garden hoses regularly.
Checking for leaks inside the home
Before assuming that an underground pipe has failed, it is important to rule out the common sources of water loss inside and around the house.
Check the toilets
A running toilet cistern is one of the easiest leaks to overlook.
The toilet may not make much noise, but water can continually pass from the cistern into the bowl because of a worn inlet valve, outlet valve or internal seal.
Sydney Water suggests placing a small piece of dry toilet paper against the back of the toilet bowl. It should remain dry between flushes. If it becomes wet, water may be leaking from the cistern into the bowl.
Also listen for a toilet that:
Refills when nobody has flushed it
Makes a faint hissing sound
Continually runs into the bowl
Takes an unusually long time to fill
Check every tap
Inspect kitchen, bathroom, laundry and outdoor taps.
Look for:
Dripping from the spout
Water around the handle
Moisture beneath the basin
Leaking flexible hoses
Water around the base of an outdoor tap
A leaking washer, O-ring, cartridge or fitting may be responsible.
Check appliances and connected services
Do not forget water connections serving:
Washing machines
Dishwashers
Refrigerators
Water filters
Irrigation systems
Pool-filling systems
Hot-water units
A concealed appliance hose leak may continue even when the appliance itself is not operating.
Look for signs of concealed moisture
Possible warning signs include:
Damp walls or cabinetry
Mould growth
Peeling or bubbling paint
Stained ceilings
Warped flooring
Musty smells
Reduced water pressure
The sound of water running behind a wall
An unexplained increase in the water bill
Wet patches on lawns and damp walls are also recognised signs of a possible leak.
Isolation Valve Installation
The existing copper water service before new isolation valves were installed for testing.
New isolation valves installed to separate the house plumbing from the underground water service.
Why did we install an isolation valve?
The existing pipework at the Pymble property did not have a suitable house isolation point that allowed us to separate the internal plumbing from the underground water service.
We installed a new isolation point into the visible copper pipework entering the property.
The house isolation valve—also commonly called a shut-off valve or ball valve—allows the plumbing within the home to be turned off independently.
This is important because turning the valve off prevents water from entering the house while the underground pipe between the meter and the new valve remains pressurised.
We could then observe the water meter again.
What did the isolation test tell us?
After the plumbing inside the house was isolated, the water meter continued registering water flow.
This meant the water was unlikely to be escaping from a tap, toilet, appliance or pipe located after the new isolation valve.
Instead, it indicated a likely leak along the underground water service between the meter and the house.
This test helps narrow down the investigation before excavation begins. It does not identify the exact point of failure, but it separates the underground service from the plumbing inside the building.
What happens after an underground leak is suspected?
The next step is to locate the damaged section of pipe as accurately as possible.
The investigation may begin with a visual inspection for:
Water pooling above ground
Damp or muddy soil
Unusually green or fast-growing grass
Soft or sunken ground
Moisture around paving
Water emerging near retaining walls
Known pipe joints
Previous repair locations
Changes in the likely direction of the pipe
A visible wet patch may help identify the area, but underground water does not always rise directly above the damaged pipe. It can travel through soil, beneath paving or along trenches before becoming visible elsewhere.
Where a leak cannot be identified visually, further concealed-leak investigation may be required. Depending on the property, this can involve pipe-location equipment, acoustic listening devices, pressure testing or other specialised methods.
Can the leaking section simply be repaired?
Sometimes.
A targeted repair may be appropriate when:
The leak location can be identified accurately
The surrounding pipe remains in sound condition
The damaged section is accessible
The failure appears isolated
Excavation will not cause unnecessary damage
However, replacing the water service from the meter to the house may provide a better long-term result when:
The pipe is badly corroded or deteriorated
There have been several previous leaks
The exact leak location cannot be determined
The existing pipe has multiple weak sections
A repair would leave ageing pipework in the ground
Repeated excavation would cost more than replacement
The correct approach depends on the pipe condition, its location, access and the likelihood of further failures.
How homeowners can perform a basic water-meter leak test
Homeowners can complete an initial check before calling a plumber.
Turn off all taps inside and outside the home.
Make sure toilets have finished filling.
Turn off the dishwasher and washing machine.
Check that irrigation systems are not running.
Avoid using showers, sinks and toilets during the test.
Find the water meter, usually near the front boundary.
Take a clear photo of the reading.
Wait at least one hour without using water.
Take another photo and compare the readings.
If the numbers have changed, there is likely water flowing somewhere on the property. A larger change generally indicates a greater rate of water loss.
For a very slow leak, an overnight test may make the change easier to identify—provided nobody uses any water during that time.
Keep the area around your water meter clear
Homeowners should also keep the meter visible and accessible.
Remove excessive soil, leaves, weeds and plants from around it so the reading can be checked and the meter can be accessed for inspection or maintenance.
Sydney Water recommends keeping at least 30 centimetres of clear space around the meter. Sydney Water maintains the meter itself, while property owners are generally responsible for the other private pipes and fittings supplying their buildings and taps.
If the leak appears to be coming from the meter itself or from pipework on the street side of the meter, contact Sydney Water to confirm responsibility before arranging private excavation.
Do not ignore a moving water meter
A water meter that continues moving when no water should be in use warrants investigation.
Waiting may result in:
Higher water bills
Ongoing water loss
Saturated ground
Damage beneath paving or landscaping
Moisture reaching the building
A minor pipe failure becoming more severe
Where the source cannot be found through a basic inspection, a licensed plumber can check the fixtures, test the water service and help determine whether the leak is inside the house or underground.
Water leak investigation in Pymble and the North Shore
Precision Pipes provides water leak investigation and plumbing repairs for homeowners in Pymble, across the North Shore and throughout the Hills District.
At this property, installing a suitable isolation point allowed us to separate the internal house plumbing from the underground service. Because the water meter continued registering water flow after the house was isolated, the investigation could then focus on the underground pipe between the meter and the home.
If your water meter is still moving when every tap and appliance is turned off, arrange an inspection before the leak causes further water loss or property damage.
FAQ
Why is my water meter moving when all the taps are off?
Does a moving water meter always mean there is an underground leak?
How does a house isolation valve help find a leak?
Should I repair or replace an underground water pipe?
Can I receive help with a high water bill caused by a hidden leak?
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Investigating a Concealed Water Leak in Pymble