A high water bill is usually caused by a hidden leak, a running toilet, a dripping tap, or an inefficient hot water system. Most homeowners do not notice the problem until the bill arrives because these faults waste water silently around the clock.
If your water bill has jumped unexpectedly, older homes across South Sydney are especially vulnerable. Ageing pipes, worn tap washers, and failing toilet cisterns all contribute to water waste that shows up on your next Sydney Water bill. At Steve Bennett Plumbing, we track down the source of high water bills across St George and Sutherland Shire every week. This guide covers the common causes, how to test your meter, what you can check yourself, and when you need a licensed plumber.
Why Do Water Bills Spike Without Warning?
Your water bill reflects the total volume of water that passes through your meter during the billing period. Sydney Water reads meters quarterly and charges per kilolitre of usage. When a leak or fault develops between readings, it runs continuously for weeks or months before you see the financial impact.
A dripping tap losing one drop per second wastes roughly 12,000 litres per year. A running toilet cistern can waste 60,000 to 90,000 litres per year, depending on the severity. A hidden pipe leak in a wall or under a slab can waste hundreds of litres per day. None of these produces obvious signs until the bill arrives or physical damage appears.
Understanding this matters because a high water bill is a symptom, not the problem itself. The bill tells you that water is going somewhere it should not. Your job is to find where.
The Most Common Causes of a High Water Bill
The following causes account for the vast majority of unexpectedly high water bills in Sydney homes:
Running Toilet Cistern
A toilet cistern that leaks into the bowl is the single biggest cause of high water bills in residential homes. The flush valve seal wears out over time and allows a constant trickle from the cistern into the bowl. You may not hear it. You may not see it. But your meter records every litre. A severely leaking cistern can waste 60,000 litres or more per year, adding hundreds of dollars to your bill.
Dripping Taps and Mixers
A dripping tap seems minor, but even a slow drip adds up over a full billing quarter. Worn washers, damaged cartridges, and corroded valve seats all cause drips that persist 24 hours a day. Multiple dripping taps across a home compound the waste. A tap and mixer repair is one of the fastest ways to bring your bill back down.
Hidden Pipe Leaks
Leaks inside walls, under concrete slabs, or in the supply line between the meter and the house are the hardest to detect. Signs include damp patches on walls, mould growth, warped flooring, or unexplained wet spots in the garden. These leaks can run for months before they are noticed. If you suspect a hidden leak, book leak detection before the damage worsens.
More: Leaking Pipe in Wall: Signs and Solutions
Faulty Hot Water System
A hot water system with a stuck pressure relief valve, a failed tempering valve, or a leaking tank connection wastes both water and energy. If only your hot water bill is high, the fault is likely in the hot water unit itself. A leaking pressure relief valve that drips into the drain can waste thousands of litres per quarter without any visible sign inside the house. The Australian Government energy guide notes that hot water accounts for roughly 25 per cent of household energy use, so a faulty system hits both your water and energy bills.
Outdoor Water Use and Irrigation Leaks
Garden hoses left running, leaking irrigation connections, and automated sprinkler systems set to run too frequently all drive up water usage. A cracked underground irrigation line can waste significant amounts of water with no visible surface signs. Check hose connections, sprinkler heads, and any buried irrigation lines for damp patches or unusually green spots.
Inefficient Appliances and Fixtures
Older toilets, showerheads, and washing machines use far more water per cycle than modern water-efficient models. A pre-2005 single-flush toilet uses roughly 11 litres per flush compared to 3 litres for a modern dual-flush half-flush. Upgrading to WELS-rated water-efficient products can reduce household water consumption significantly.
Faulty Water Meter
In rare cases, the meter itself is inaccurate. If you have ruled out every other cause and your bill remains high, contact Sydney Water to request a meter accuracy test. Sydney Water will test the meter at no charge if you believe it is faulty.
How to Test Your Water Meter for Leaks
The meter test is the fastest way to confirm whether you have a leak. It takes 15 minutes and requires no tools:
Step 1: Turn Off All Water
Turn off every tap, shower, washing machine, dishwasher, and any automated irrigation system. Make sure no one in the household uses any water during the test.
Step 2: Record the Meter Reading
Locate your water meter, usually near the front boundary of your property. Write down the exact reading, including the red numbers or dials that show litres.
Step 3: Wait 15 Minutes
Do not use any water for 15 minutes.
Step 4: Check the Meter Again
If the reading has changed or the flow indicator (small triangle or dial on the meter face) is moving, water is flowing somewhere in your system. You have a leak.
Step 5: Isolate the Source
Turn off the isolation valve at your house (usually near the hot water system or at the front tap). Check the meter again. If the meter stops, the leak is inside the house. If the meter keeps running, the leak is in the supply line between the meter and the house, which requires a licensed plumber.
More: 9 Basic Plumbing Maintenance Tips & Signs of Damage
Quick Diagnostic: Where Is the Water Going?
Once you have confirmed a leak through the meter test, the symptom pattern helps you narrow down the source:
Your Bill Is High But Nothing Looks Wrong
This is almost always a silent toilet cistern leak or a hidden pipe leak. Perform the food colouring test on every toilet in the house. Drop a few drops of food colouring into the cistern, wait 10 minutes without flushing, and check the bowl. If colour appears, the flush valve seal is faulty.
Your Hot Water Bill Is Unusually High
If your hot water usage has spiked, the fault is likely in the hot water system itself. Check the pressure relief valve overflow pipe for dripping. Check for dampness around the base of the tank. A hot water system repair visit can identify and fix the source in one appointment.
Your Bill Spiked Suddenly After Moving In
First water bills in a new home are often higher than expected. This can be caused by a longer billing period than you assumed, leaks in the property that were not disclosed, unfamiliarity with local water rates, or higher baseline usage than your previous home. Compare your usage per day against Sydney Water’s published average. If it is significantly higher, investigate for leaks.
Your Bill Is Higher in the Summer
Seasonal increases are normal. Garden watering, filling pools, pressure washing, and longer showers all drive up summer usage. Check your quarterly usage against the same period last year. If usage is higher than expected for the season, a leak may be compounding the seasonal increase.
Meter Keeps Running With Everything Off
If the meter moves with every fixture turned off and the house isolation valve open, the leak is in the supply line between the meter and the house. This pipe runs underground, and leaks are not visible from the surface. You need a licensed plumber with leak detection equipment.
What to Do Before Calling a Plumber
Several safe checks can help you identify or rule out common causes before booking a service call:
Perform the Food Colouring Test on Every Toilet
This test catches the most common cause of high water bills. Drop food colouring into each cistern, wait 10 minutes without flushing, and check the bowl. Colour in the bowl means a leaking flush valve seal. This single test can identify the fault that is costing you hundreds of dollars per year.
Check Every Tap and Mixer
Turn off every tap in the house firmly and check for drips. Look at the base of mixer taps and underneath sinks for seepage. Pay attention to outdoor taps, laundry taps, and any fixtures you rarely use. A tap that drips once per second wastes roughly 12,000 litres per year.
Inspect the Hot Water System
Check the pressure relief valve overflow pipe for any dripping or moisture. Look for dampness, rust, or pooling water around the base of the unit. Listen for hissing or running water sounds near the system. If the unit is older than 10 years, component wear is likely contributing to water waste.
Check Outdoor Hoses and Irrigation
Walk the perimeter of the property and inspect all hose connections, outdoor taps, and irrigation lines. Look for damp patches, puddles, or unusually green grass that could indicate a buried leak. Check automated sprinkler timers to confirm they are set correctly.
Review Your Sydney Water Bill
Compare your usage in kilolitres against the previous quarter and against the same quarter last year. Sydney Water bills include a daily average consumption figure. If this has jumped without a change in household habits, a leak is the most likely explanation.
When to Call a Licensed Plumber
Call a plumber if the meter test confirms a leak, if you cannot locate the source after basic checks, if the leak is in the supply line between the meter and the house, if you suspect a hidden pipe leak behind a wall or under a slab, or if your hot water system is leaking. All plumbing repair work in NSW must be carried out by a licensed plumber. You can verify any plumber’s licence through Service NSW before booking.
Why High Water Bills Are Common in South Sydney’s Older Homes
The housing stock and plumbing infrastructure across St George and Sutherland Shire make high water bills a recurring issue:
Ageing Galvanised Pipes in Post-War Housing
Homes across Hurstville, Kogarah, and Peakhurst built in the 1950s to 1970s often still have original galvanised steel supply pipes. These pipes corrode from the inside over decades, developing pinhole leaks that weep continuously. The leaks are too small to see but large enough to move your meter.
Original Tap Washers and Cistern Seals
Mortdale, Oatley, and Carlton have many homes where bathroom and laundry fixtures have never been updated. Original tap washers harden and crack over time, causing persistent drips. Original cistern seals perish and allow constant water flow into the bowl. These small leaks add up to large bills.
Coastal Corrosion on Outdoor Plumbing
Cronulla, Caringbah, and Sans Souci face salt-heavy air that accelerates corrosion on outdoor taps, hose fittings, and exposed pipe connections. These corroded fittings develop slow leaks that run unnoticed into garden beds and drainage.
Older Hot Water Systems Past Service Life
Hot water systems across Miranda, Sylvania, and Kirrawee are often 10 to 15 years old. Pressure relief valves on these ageing units begin to drip continuously, wasting water directly into the drain. Homeowners rarely notice because the overflow pipe runs outside.
Mature Gardens with Ageing Irrigation
Menai and Engadine have established properties with mature gardens and older irrigation systems. Buried poly pipe connections degrade over time, cracking at joints and leaking underground. The surface shows nothing, but the meter keeps turning.
How a Licensed Plumber Diagnoses a High Water Bill
When DIY checks do not pinpoint the source, here is what to expect from a professional:
Meter Test and Zone Isolation
A licensed plumber starts with a comprehensive meter test, then systematically isolates zones by shutting off sections of the plumbing system. This narrows the leak to a specific area: the supply line, the internal cold water network, the hot water system, or the outdoor plumbing.
Acoustic Leak Detection
For hidden leaks behind walls, under slabs, or in buried supply lines, acoustic listening equipment amplifies the sound of water escaping through a crack or joint. This technology pinpoints the leak location without cutting tiles or digging. Steve Bennett Plumbing uses advanced leak detection equipment to locate faults with minimal disruption to your home.
Fixture-by-Fixture Inspection
Every toilet, tap, mixer, hot water system, and outdoor connection is tested individually. Cisterns are checked for flush valve leaks. Taps are checked for washer wear and valve seat damage. Hot water pressure relief valves are tested for drip rate. This thorough approach ensures nothing is missed.
Repair and Replacement
Once the leak is found, the plumber carries out the repair on the spot, where possible. Common fixes include toilet cistern valve replacement, tap washer or cartridge replacement, pressure relief valve replacement, pipe joint repair, and supply line repair. Most of these are completed in a single visit. You can learn more about our team and our 40-year history of helping South Sydney homeowners reduce water waste.
After tracking down a hidden leak for a homeowner in our service area, Steve Bennett Plumbing received this feedback: “Great service. Friendly and a pleasure to deal with. They carry out the work quickly and extremely well. I wouldn’t be using anyone else.” Christine Duncan. That is the standard of diagnostic work a high water bill demands.
More: How to Repair a Leaking Tap Like a Pro
How to Prevent High Water Bills
Once the immediate issue is resolved, these habits keep your water usage and bills under control:
Fix Drips Immediately
A dripping tap or running toilet that you “will get to later” costs you money every day it runs. Book a repair as soon as you notice any drip, hiss, or trickle. The repair cost is almost always less than one quarter of the elevated water bills.
Test Your Meter Every Quarter
Run the 15-minute meter test at the start of each billing cycle. This catches new leaks early, before they have three months to run up your bill. Write down the reading and compare it to the previous quarter.
Service Your Hot Water System Regularly
Book a professional service every 3 to 5 years. The plumber checks the pressure relief valve, inspects connections for drips, and tests the thermostat. A well-maintained system wastes less water and lasts longer. Steve Bennett Plumbing offers scheduled plumbing maintenance visits across our full-service area.
Upgrade Inefficient Fixtures
Replace pre-2005 single-flush toilets, old showerheads, and dripping taps with WELS-rated water-efficient products. Modern dual-flush toilets use 3 to 4.5 litres per flush compared to 11 litres for older models.
Check Irrigation Systems Before Summer
Inspect all sprinkler heads, hose connections, and buried poly pipe joints before the summer watering season. Fix any drips or cracks before they run for months undetected.
Know Your Baseline Usage
Write down your daily average water consumption from each bill. Sydney Water includes this figure on every invoice. If it rises without a change in household habits, investigate immediately rather than waiting for the next bill.
Areas We Service
Steve Bennett Plumbing serves homeowners across the St George and Sutherland Shire regions. Our service area includes Hurstville, Kogarah, Peakhurst, Sans Souci, Mortdale, Oatley, Carlton, Miranda, Cronulla, Engadine, Caringbah, Kirrawee, Sylvania, Menai, and Gymea.
Find the Leak and Fix Your Water Bill in Sydney
If your water bill has spiked and you cannot find the source, do not pay another inflated quarter. A hidden leak left running for three more months costs far more than a single diagnostic visit. Finding and fixing the fault now puts money back in your pocket from the next bill onwards.
Call Steve Bennett Plumbing today on 02 9538 7864 or reach our emergency line on 0413 158 600. Every callout includes a $0 call-out fee, a fixed-price quote, and same-day service where possible. Our lifetime labour warranty means the repair stays fixed. We respond to emergencies when a burst pipe or major leak needs urgent attention.
Frequently Asked Questions
Why is my water bill so high all of a sudden?
A sudden spike is almost always caused by a new leak. Running toilets, burst pipes, stuck pressure relief valves, and cracked supply lines all develop without warning. Run the 15-minute meter test to confirm whether water is flowing when everything is turned off.
Why is my hot water bill so high?
If only your hot water usage has increased, the fault is likely in the hot water system. A dripping pressure relief valve, a leaking tank connection, or a stuck tempering valve all waste heated water. Check for moisture around the unit and the overflow pipe.
Why is my first water bill so high?
First bills in a new home are often higher than expected because the billing period may be longer than you assumed, pre-existing leaks may not have been disclosed, or your baseline usage is higher than your previous property. Compare your daily average to Sydney Water’s published benchmarks.
How do I check if I have a water leak at home?
Turn off all water in the house. Record your meter reading. Wait 15 minutes without using any water. Check the meter again. If the reading has changed or the flow indicator is moving, you have a leak. Isolate sections of the plumbing to narrow down the source.
Can a running toilet really increase my water bill?
Yes. A running toilet cistern can waste 60,000 to 90,000 litres per year, depending on the severity of the leak. This adds hundreds of dollars to your annual water bill. The food colouring test confirms whether your cistern is leaking.
When should I call a plumber about a high water bill?
Call a licensed plumber if the meter test confirms a leak you cannot find, if the leak is in the supply line, if you suspect a hidden pipe leak behind a wall or under a slab, or if your hot water system is dripping. Professional leak detection locates the source without unnecessary damage to your home.
