The cause will depend on whether you have a gas, electric, storage or continuous-flow hot water system.

Common causes of no hot water from a gas system include:

• The gas meter or isolation valve has been switched off

• An LPG bottle is empty or disconnected

• The pilot light has gone out on an older gas hot water system

• The ignition system is not operating

• The unit has lost electrical power

• The thermostat or main controller has failed

• The gas control valve is faulty

• Wind, rain or condensation has affected the burner or pilot assembly

• The heat exchanger or storage tank has developed a fault

• The water flow is too low to activate a continuous-flow system

A pilot light that repeatedly goes out can indicate a larger problem. It may be caused by the age or condition of the unit, poor combustion, water entering the burner area or a damaged heat exchanger. For safety, gas components should always be inspected by a licensed gas plumber.

Common electric hot water faults include:

• A faulty thermostat

• A failed heating element

• A tripped circuit breaker or safety switch

• A problem with the electrical supply

• A faulty over-temperature cut-out

• An off-peak power or timer issue

• The tank has run out of stored hot water and has not reheated

• Internal corrosion or failure of an older storage tank

If the circuit breaker continues to trip, do not repeatedly reset it. The hot water system should be professionally inspected.

Some plumbing faults can stop hot water from reaching your taps even when the hot water unit itself is operating correctly.

A burst or leaking hot-water pipe can make it appear that your storage hot water system is not heating properly. If hot water is escaping from an underground, under-slab or concealed pipe, the storage tank may continuously lose heated water and refill with cold water. The tank itself remains full, but it may be unable to heat the incoming water quickly enough to keep up with the leak. As a result, the water reaching your taps may be cold or only lukewarm.

Possible signs of a concealed hot-water leak include:

• The water meter continues moving when nothing is using water

• Your hot water runs out unusually quickly

• The hot water system appears to operate continuously

• Higher-than-normal water, gas or electricity bills

• Warm or damp areas on floors, paving or concrete

• The sound of running water when all taps are off

• Reduced hot-water pressure

• Unexplained moisture, mould or water damage

The Plumbing & Electrical Co. has specialist water leak detection equipment and experienced leak detection technicians. We use acoustic, thermal and pressure-testing equipment to help locate concealed leaks while minimising unnecessary damage to walls, floors and surrounding areas. If specialist leak detection is required, we will explain the process and confirm the applicable charges before proceeding.

You can perform a simple water-meter test before booking an inspection:

1. Turn off every tap and water-using fixture in the property.

2. Make sure the washing machine, dishwasher, reticulation, toilets and other appliances are not filling or operating.

3. Do not turn off the water supply at the meter.

4. Record the meter reading or look closely at its small leak-detection dial.

5. Wait approximately five to ten minutes without using any water.

6. Check whether the meter reading or dial has moved.

If the meter continues moving while everything is turned off, water is likely escaping somewhere within the property.

This test can indicate that a leak may be present, but it cannot confirm whether the leak is on the hot or cold water pipework or identify its location. Further professional testing will be required.

A failed tempering valve is a very common cause of lukewarm or cold water at the taps. This valve blends hot and cold water to deliver water at a safe temperature. When it fails, excessive cold water may enter the hot water line. The typical cost to supply and install a replacement tempering valve is approximately $350.00–$400.00.

Final pricing is confirmed after inspection and may vary depending on:

• The type of valve required

• Accessibility

• The existing pipework

• Whether additional plumbing alterations are needed

• Any other faults discovered during testing

A cross-connection allows cold water to push into the hot water pipework. This can make every hot tap in the property run cold or lukewarm.

Possible causes include:

• Recent plumbing work connecting a cold line to a hot line

• A faulty mixer tap or internal cartridge

• A damaged tap set

• A capped or blocked shower outlet with the taps or mixer left open

• An incorrectly connected appliance or fixture

Cross-connections can be difficult to locate because the problem may appear at a different fixture from the one causing it. We isolate and test the plumbing systematically to identify the source.

Whether your hot water unit should be repaired or replaced depends on:

• The age of the system

• The component that has failed

• The condition of the tank or heat exchanger

• The availability and cost of replacement parts

• The likelihood of further failures

• The running efficiency of the existing unit

If a hot water system is more than eight years old and has suffered a significant failure, we will generally recommend comparing the repair cost with replacement. We’ll explain the available options so you can make an informed decision.

The best way to resolve a no-hot-water problem is to test the system properly rather than replacing parts based on guesswork.

During the inspection, we will:

• Identify your hot water system type

• Check the available gas or electrical supply

• Test the system’s operation

• Inspect the relevant valves and visible pipework

• Check for possible hot-to-cold cross-connections

• Check for signs of a burst or leaking hot-water pipe

• Determine the most likely failed component

• Explain whether repair or replacement is the better option

• Provide pricing for the recommended work

The diagnostic fee covers the initial inspection and standard testing. Replacement parts, repairs, specialist leak detection and additional work are not included unless clearly stated and will be quoted separately. Some intermittent, underground or complex faults may require further testing.

Before booking a service, you can safely check whether:

• Other gas appliances are working

• Your gas meter or LPG supply is on

• The hot water unit has electrical power

• A circuit breaker or safety switch has tripped

• The problem affects every hot tap or only one fixture

• The system is displaying an error code

• The water meter continues moving when everything is turned off

Do not remove covers, dismantle the unit or work on gas or electrical components yourself. If you suspect a burst pipe, arrange an inspection promptly to limit water loss and potential property damage. If you smell gas, turn off the gas supply if it is safe to do so, avoid flames and electrical switches, move away from the area and contact your gas distributor’s emergency service.

Whether the problem is inside the hot water system, a failed tempering valve, a plumbing cross-connection or a concealed burst pipe, The Plumbing Co. can identify the cause and recommend the most practical solution.

This can be caused by a failed thermostat, heating element, gas ignition component, controller or tempering valve. A plumbing cross-connection or concealed burst hot-water pipe can also cause cold or lukewarm water at the taps.

Yes. If heated water is continually escaping from a damaged pipe, the storage tank will keep refilling with cold water. The system may be unable to reheat that water quickly enough, leaving you with cold or lukewarm water.

Turn off all taps, fixtures and water-using appliances, then monitor the water meter for five to ten minutes. If the meter continues moving, there may be a leak within the property. Professional testing is required to determine its location and whether it involves hot or cold pipework.

Yes. We have specialist acoustic, thermal and pressure-testing equipment that can help locate concealed water leaks while minimising unnecessary damage to the property.

A faulty tempering valve is one of the most common causes. Other possibilities include an incorrect temperature setting, a failing heating component, excessive demand, cold water crossing into the hot pipework or heated water escaping from a concealed pipe.

Our initial hot water diagnostic service is $180.00. If specialist leak detection, repairs or replacement parts are required, we will explain the recommended next step and confirm the applicable pricing.

A typical tempering valve replacement costs approximately $350.00–$400.00, including supply and installation. Final pricing depends on the valve type, accessibility, pipework and the condition of the existing installation.

CAN A MIXER TAP CAUSE THE WHOLE HOUSE TO LOSE HOT WATER?

Yes. A faulty mixer cartridge can create a cross-connection that allows cold water to feed into the hot water pipework. This can affect multiple taps throughout the property.

Yes. We diagnose faults affecting gas and electric hot water systems, including storage tanks and continuous-flow units. After testing, we’ll explain whether repair or replacement is the best option.

That depends on its condition and the failed component. For units older than eight years with a significant fault, it is usually worth comparing the repair cost with the cost and benefits of replacement.