Why Is My Water Bill So High? 6 Causes Gold Coast Homeowners Miss

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Your water bill just arrived, and the number is noticeably higher than usual. Nobody's mentioned a new pool, a garden overhaul, or extra houseguests. So where is all that extra water actually going?

A sudden or gradual jump in your water bill almost always has a specific, findable cause. Most of the time, it's something small that's easy to miss day to day, like a toilet that's silently running or a tap washer that's worn out. Occasionally, it points to something more serious happening underground or behind a wall.

Here are the six most common causes Gold Coast homeowners overlook, and how to check for each one before you call a plumber.

1. A Running or Silently Leaking Toilet

This is, by a wide margin, the most common cause of an unexplained water bill increase. A worn flapper or fill valve can let water trickle from the tank into the bowl continuously, often without any audible running sound, wasting hundreds of litres a day.

How to check:
Add a few drops of food colouring to the tank and wait 15 minutes without flushing. If colour appears in the bowl, water is leaking through the flapper seal.

We've covered this in detail, including all the causes and fixes, in our guide to why your toilet is running.

2. A Dripping Tap or Fixture

A slow drip looks harmless, but a tap losing just one drip per second wastes roughly 20 litres a day, more than 7,000 litres a year. Outdoor taps are especially easy to overlook since they're not in daily view the way kitchen or bathroom taps are.

How to check:
Walk the property and check every tap, including outdoor taps, hose connections, and any irrigation fittings, for drips or damp patches underneath.

If you find one, our guide on how to fix a dripping tap quickly covers the simple fix.

3. A Hidden Underground or Slab Leak

This is the cause homeowners are most likely to miss entirely, because there's often no visible sign at all. A leak in a pipe under your slab or lawn can waste enormous volumes of water while showing nothing more than a persistently high bill, and occasionally, a warm patch on the floor or an unexplained damp area in the yard.

How to check:
Turn off every tap and appliance in the house, then check your water meter. If the meter is still moving, water is escaping somewhere between the meter and your fixtures.

We walk through this exact process in our guide to the water meter test, and if you suspect the leak is under the slab specifically, our slab leak signs guide covers what to look for.

4. A Faulty Pressure Limiting Valve

If your home's water pressure is running higher than it should, it doesn't just stress your pipes and fittings, it also pushes more water through every fixture than necessary every time you turn one on. A failed or missing pressure limiting valve is a common, often overlooked contributor to a creeping water bill.

How to check:
If your taps feel unusually forceful, or you've had multiple fittings fail or start leaking around the same time, high pressure is a likely factor. Our guide on how high water pressure secretly damages your pipes explains the signs to look for and how a pressure limiting valve fixes it.

5. An Old, Inefficient Toilet or Fixture

If your home still has original fittings from before the early 2000s, it may be using significantly more water per use than a modern fixture, without anything being "broken" at all. Older toilets can use 9 to 12 litres per flush compared to 3 to 4.5 litres for a modern dual-flush model, and older showerheads can use double the flow rate of a modern water-efficient one.

How to check:
Look for a WELS (Water Efficiency Labelling Scheme) star rating on your toilets, showerheads, and taps. No rating usually means an older, less efficient fixture.

6. A Leaking or Overflowing Cistern, Hot Water System, or Irrigation Line

A few less obvious culprits round out the list:

• An overflowing toilet cistern where the fill valve doesn't shut off properly, constantly running water down the overflow tube
• A leaking hot water system, particularly around the pressure relief valve or tank seams on an ageing unit
• A stuck or leaking irrigation controller watering the garden on a schedule you're not aware of, or continuing to run after a fault

How to check:
Check your hot water system for pooling water or rust stains around its base, and if you have irrigation, confirm the controller's schedule matches what you'd expect and that no zones are stuck running.

What to Do If You Can't Find the Cause

If you've worked through this list and the water meter test still shows usage you can't explain, the leak is likely hidden underground, inside a wall cavity, or under the slab, none of which are practical to find without the right equipment.

Professional leak detection uses acoustic listening devices and thermal imaging to pinpoint a leak's exact location without needing to dig up your yard or break into walls speculatively. This is almost always faster and cheaper than guessing.

Get to the Bottom of a High Water Bill

An unexplained jump in your water bill is always worth investigating properly rather than just accepting it as "one of those things." Left unresolved, most causes on this list get worse, and more expensive, over time.

Coastal Plumbing Professionals provides professional water leak detection and repair across the Gold Coast, using non-invasive detection equipment to find hidden leaks quickly and accurately.

Call 1300 590 085 to book a leak detection inspection.

Frequently Asked Questions

How much water usage increase should trigger concern?
Compare your current bill to the same period last year, or to your typical quarterly usage, rather than just the previous bill, since seasonal factors like garden watering can explain some variation. A jump of 20% or more without an obvious explanation is worth investigating.

Can a running toilet really affect my bill that much?
Yes. A continuously running toilet can waste several hundred litres a day, which adds up to a significant, very noticeable jump on your next quarterly bill.

How do I know if a leak is on my property or the council's side?
Your water meter marks the boundary. If the meter itself is spinning while every fixture in your home is off, the leak is on your property's side and is your responsibility to fix. If you suspect the leak is between the meter and the street, contact your water authority.

Is professional leak detection expensive?
It's generally far more cost-effective than guessing and digging speculatively, since acoustic and thermal detection equipment pinpoints the exact leak location, minimising the repair work needed once it's found.

What's the fastest way to check for a leak myself?
The water meter test, turning off every fixture and appliance, then watching whether the meter still moves, is the quickest way to confirm whether water is escaping somewhere on your property before you call a plumber.

Resources

1. Water & sewerage | City of Gold Coast
2. Water Efficiency Labelling and Standards (WELS) Scheme | Australian Government
3. AS/NZS 3500 Plumbing and Drainage Standards | Standards Australia