How to Check for a Hidden Water Leak

What the signs can tell you

For the work involved, see our leak-detection service and cost guide.

Start with the Water Meter and Fault Signs

A concealed leak can show up as unexpected water use, a damp finish, an unusual warm patch or the sound of water when fixtures are off. None of those signs confirms the exact source on its own.

The safest first step is to record what is happening and check whether the water meter moves when the property should not be using water.

How to Check the Meter

If you have your own accessible meter, follow Sydney Water’s meter check:

1. Turn off taps and water-using appliances, including irrigation. Let cisterns finish filling.
2. Leave the meter tap turned on.
3. Note or photograph the complete reading, including the smaller numbers.
4. Use no water for at least one hour.
5. Compare the reading. A change means water passed through the meter during the test.

Movement can indicate water is escaping, but irrigation, pools, filters, automatic appliances and shared supplies may need to be isolated before the result is clear.

A stationary meter does not rule out a waste-pipe leak that occurs only when a fixture drains, an intermittent supply leak or a waterproofing problem. Keep investigating unexplained dampness even if this check is clear. Do not remove covers, open walls or disturb electrical areas to investigate.

Signs Worth Recording

• A water-use increase that does not match household activity
• Damp, discoloured or bubbling finishes
• A sound of running water when fixtures are off
• An unusual warm area on a floor
• Water appearing outside near the route between meter and building
• A leak that stops when one service or fixture is isolated

Mark the affected area and note whether it changes after showers, appliance use, rain or irrigation. That timing can help separate plumbing water from other moisture sources.

Common Places to Check Safely

Look only at accessible areas:

• Under sinks and vanities
• Around toilet and appliance connections
• Near the hot water unit and visible valves
• At outdoor taps and exposed pipework
• Along the visible route from meter to house

If water is near electrical equipment, a ceiling is sagging or a surface feels unsafe, keep clear and arrange urgent help.

How Leak Detection Narrows the Source

Different leaks need different tests:

• Meter and isolation checks help identify the affected service or section.
• Acoustic listening may help with an active pressurised leak.
• Thermal imaging can show useful temperature differences around some hot-water leaks.
• Moisture readings help compare affected and unaffected finishes.
• Pressure testing may help confirm loss on an isolated line.
• CCTV inspection is for the inside of accessible drainage pipe, not a general view through walls.

No single tool suits every building. Some leaks still need a targeted opening before the pipe can be confirmed and repaired.

Repair Comes After the Source Is Understood

The repair may involve a fitting, a short pipe section, an external water service or broader pipe renewal. Access, pipe material, surrounding finishes and whether failures have happened before all affect the recommendation.

Pipe relining is a method for suitable damaged drainage pipe. It is not a general repair for a concealed pressurised water leak.

What to Send with an Enquiry

Send the meter behaviour, affected rooms, photos, when the signs appear and any recent plumbing, building, pool or irrigation work. For active water damage, call. For a suspected concealed leak, see the leak-detection service.

Call 0404 939 121 if water is actively escaping, or send the meter and fault details online.

For supply-side checks, see Sydney Water’s current supply updates and water-meter leak checks.