Unexplained Water Bill Spike? You Probably Have a Hidden Leak

If your water bill has jumped and your usage hasn't changed, there's a very good chance you have a hidden leak. A leaking pipe can waste thousands of litres of water a month — silently, underground, or behind a wall where you'll never see it.

Here's how to tell if you have a hidden leak, where they most commonly occur, and what to do about it.

How Much Is Too Much?

A typical Sydney household uses about 200–300 litres per person per day. If your bill has jumped 30% or more and you can't explain it (no new pool, no extra houseguests, no new irrigation system), a leak is the most likely culprit.

A slow drip from a single tap wastes about 20–30 litres a day. A leaking toilet cistern can waste 200–400 litres a day. A cracked underground pipe can waste thousands.

The Most Common Hidden Leaks

1. Leaking Toilet Cistern

The most common hidden leak in Australian homes. The flapper valve at the bottom of the cistren degrades over time and lets water trickle into the bowl continuously. You won't see it, but you'll hear a faint hiss or see a slight ripple in the bowl water.

Quick test: Put a few drops of food colouring in the cistern. If colour appears in the bowl within 15 minutes without flushing, you have a leak.

2. Underground Pipe Leaks

Cracked or corroded underground water pipes leak silently into the soil. Common in homes with original galvanized steel pipes (pre-1980s construction). Look for unexplained wet patches, lush green patches in the lawn, or a hissing sound near the water meter.

3. Hot Water System Leaks

A slow leak from the temperature/pressure relief valve or the tank itself can waste significant water. Check around the base of the system for water staining or pooling.

4. Hidden Wall Leaks

Pipes inside wall cavities can leak from corroded joints. Look for bubbling paint, damp patches, or mould on walls. These leaks can cause structural damage if left.

5. Irrigation System Leaks

A cracked irrigation pipe or broken sprinkler head underground can waste enormous amounts of water. Check for soggy patches in the garden.

How to Check for a Leak

1. Turn off all taps and water-using appliances in the house.
2. Check your water meter. If the dial is still moving, water is flowing somewhere — you have a leak.
3. Note the reading, wait an hour without using any water, then check again. Any change confirms a leak.

What to Do

Hidden leaks don't fix themselves. The longer you wait, the more water you waste and the more damage you risk — especially if the leak is inside a wall or under your slab.

At Tru Blu Plumbing, we use acoustic leak detection and thermal imaging to pinpoint the exact location of hidden leaks without digging up your entire property. Once located, we repair the leak with minimal disruption.

Call 0452 317 892 if you suspect a hidden leak — early detection saves water, money, and structural damage.