Common Causes of Water Leaks at Home

Dripping Taps and Failing Tap Washers

A dripping tap is one of the most common — and most underestimated — water leaks in Australian homes. A tap dripping once per second wastes over 30 litres per day, or roughly 11,000 litres per year. The cause is almost always a worn tap washer or cartridge inside the tap mechanism. In older compression taps this is a rubber washer that wears out over years of use. In modern ceramic disc taps it's a ceramic cartridge that can crack or collect mineral deposits. Both are straightforward to replace and the repair typically takes under an hour.

Running Toilet Cisterns

A continuously running toilet is the second most common household water leak, and often goes unnoticed because it's relatively quiet. Water passes continuously from the cistern into the toilet pan through a worn flush valve or a misadjusted fill valve float. The leak can be confirmed with the food colouring test — add a few drops to the cistern and check whether colour appears in the pan without flushing. A running cistern can waste 400 litres per day or more, and is one of the most common explanations for an unexpectedly high water bill.

• Worn flush valve (flapper) — most common cause of running cistern
• Incorrect float height — cistern overfills and water enters overflow pipe
• Cracked cistern — rare but causes slow persistent leak at base
• Loose supply connection — small leak at wall fitting, often behind cistern

Pipe Joints and Fittings

Joints between pipes and fittings are natural weak points. Over time, the thread sealant or rubber gaskets at threaded joints dry out and allow small amounts of water past. Push-fit fittings can work loose if disturbed by renovation work or ground movement. In older properties with galvanised steel pipes, corrosion at joints is common — the galvanised coating wears off the interior first, then rust weakens the pipe wall until a pinhole or joint failure occurs.

These leaks often start small and invisible — inside wall cavities or under floors — and become evident only when water damage becomes visible as staining, dampness, or mould.

Hot Water Systems

Hot water systems are a frequent source of leaks, particularly as they age. The temperature and pressure relief (T&P) valve is designed to release water if pressure or temperature inside the tank becomes too high — so a small amount of occasional dripping from this valve is normal during heating cycles. Constant dripping or flowing from the T&P valve indicates excessive pressure (often a failing PLV) or a fault with the valve itself. A weeping relief valve that's left running will continue to deteriorate and can fail suddenly.

Tank corrosion is the other major hot water system leak source. Once a storage tank begins to corrode through internally, the tank cannot be repaired — it needs replacement. Signs include rusty or discoloured hot water, or visible rust staining around the base of the unit.

Underground and Slab Leaks

Water supply lines that run underground or under concrete slabs can develop leaks from ground movement, root intrusion, or corrosion over many decades. These leaks can run undetected for months or years, gradually softening soil, damaging foundations, and adding hundreds of dollars per quarter to water bills. Detection typically requires specialist equipment — pressure testing, acoustic detection gear, or thermal imaging. A licensed plumber with leak detection equipment can locate these leaks without unnecessary excavation in most cases.

• Unexplained wet patches on lawn or driveway — possible underground supply leak
• Meter ticking with all fixtures off — leak is occurring somewhere in the supply line
• High water bill with no obvious explanation — underground or slab leak
• Warm patch on floor — hot water slab leak

Appliance Connections

Washing machines, dishwashers, and refrigerators with ice makers or water dispensers all have supply line connections that can fail. Washing machine rubber hoses degrade over time and can burst suddenly — often while the machine is running unattended. Replacing rubber hoses with braided stainless steel hoses is a worthwhile upgrade that significantly reduces burst risk. Dishwasher and refrigerator connections are typically smaller-diameter flexible hoses that can crack or come loose at the connection points.