Running Out of Hot Water: Causes and Solutions Explained

In the past, you enjoyed a steady supply of hot water, but now your shower may turn cold without warning, leaving the last bather with only a lukewarm trickle. If you notice that your access to hot water is diminishing faster than before, it’s a clear indication that something is amiss. This situation could arise from changes in how your household uses hot water, issues within the hot water system itself, or concerns related to the energy source that fuels it.

This detailed guide outlines seven prevalent causes of hot water shortages in Queensland homes. It also explains how long you should expect to wait for hot water to return after it has run out, and provides practical steps you can take before contacting a plumber.

Understanding the Key Reasons Behind Hot Water Shortages

• An electric storage tank operating on an off-peak (controlled load) tariff heats water only during specified times when the electricity network supplies power, which may leave it cold until the next off-peak cycle.
• If the water is still cold the following morning, it indicates a malfunction rather than high demand.
• Common reasons for hot water shortages include an inadequately sized tank for the household’s needs, a malfunctioning heating element or thermostat, sediment build-up, a thermostat set too low, insufficient solar boosting, tariff limitations, or an ageing system.

What is the Expected Waiting Time for Hot Water to Return After Depletion?

The time you need to wait for hot water largely depends on the type of hot water system you have and the energy source it uses.

• Electric storage tank on a standard tariff: the heating element activates immediately when the water temperature drops, allowing for prompt reheating of the tank. Larger tanks equipped with smaller elements may take longer to reach the desired temperature.
• Electric storage tank on an off-peak tariff: in Queensland, these controlled load tariffs are classified as Tariff 31 or Tariff 33. Your electricity provider controls when power is delivered, meaning a tank that empties in the evening might not start reheating until the next off-peak cycle.
• Gas storage tank: the burner ignites whenever the water temperature decreases, allowing for swift reheating of the tank. If it fails to ignite, check the pilot light for potential issues.
• Gas continuous flow: these systems heat water on demand, eliminating the risk of running out. If the water turns cold, the issue likely lies with a fault, gas supply, or flow problem rather than depletion of stored hot water.
• Solar hot water: recovery is dependent on sunlight availability and the efficiency of the booster. After several cloudy days, the booster typically takes on the majority of the workload.

According to Energy Made Easy, the Australian Government’s energy comparison service, a controlled load tariff applies to larger appliances like hot water systems that operate on their own circuit, restricting power usage to specific time slots, usually overnight and on weekends (Energy Made Easy, Understanding controlled loads). If your hot water remains cold the next morning after an off-peak period, this indicates that the tank has not reheated, suggesting a fault rather than excessive demand.

For those using gas hot water systems that experience a lack of hot water, our guide on pilot light issues can guide you through the necessary initial checks.

1. Is Your Hot Water System Sufficiently Sized for Your Household?

Hot water systems are typically sized to meet the demands of the households they serve. As families grow, with teenagers taking longer showers and more people working from home, a system designed for two individuals may struggle to provide adequate hot water for a family of four.

Signs your hot water system may not be adequately sized:

• Hot water runs out after just one or two consecutive showers.
• The family must schedule shower times to prevent the last person from running out of hot water.
• The issue occurred following an increase in household size, rather than as the system aged.

If your hot water system functions correctly but lacks capacity, upgrading to a larger tank or a different type of system will solve the problem. Our guide to various hot water systems suitable for Brisbane and Moreton Bay homes compares options such as electric, gas, solar, and heat pump systems.

2. Are There Problems with the Heating Element or Thermostat in Your Electric Hot Water System?

An electric storage tank relies on its heating element to warm the water and its thermostat to regulate the heating cycle. If either of these components begins to fail, the water may heat inadequately or not at all, resulting in the tank depleting more rapidly than before.

Symptoms of a failing heating element or thermostat:

• The water is warm but does not reach the desired hot temperature.
• Hot water runs out noticeably sooner than it did a few months ago.
• The safety switch trips when the hot water system is powered on.

Both the heating element and thermostat are located behind a cover on the tank and function on mains power. Avoid attempting to open this cover yourself. A qualified plumber can assess both components and advise whether replacement is a viable option based on the tank’s age. Schedule a hot water system inspection if you notice any of these signs.

3. Has Sediment Built Up in Your Hot Water Tank?

Over time, minerals in the water settle at the bottom of a storage tank. This sediment layer occupies space that should be filled with hot water and can coat the heating element in electric tanks, hindering the heating process.

Signs of sediment accumulation in the hot water tank:

• Rumbling or popping sounds coming from the tank while heating.
• Hot water depletes faster despite no changes in consumption patterns.
• Cloudy, gritty, or rusty water coming from the taps.

During a service visit, a plumber will flush the sediment from the tank and inspect the sacrificial anode, a rod inside the tank designed to corrode and protect the tank from deterioration. Our article on hard water and hot water systems in Caboolture explores how water quality affects a tank’s lifespan.

4. Is Your Hot Water Thermostat Set at an Inadequate Temperature?

Some individuals lower the thermostat setting to save energy or to avoid excessively hot water at the taps. cooler water in the tank depletes more rapidly, as less cold water mixes during showers, resulting in greater consumption of the tank’s contents.

The Queensland Government recommends that stored hot water in homes should be heated to a minimum of 60°C to prevent the growth of bacteria such as Legionella. New and replacement systems must include a temperature control device to ensure that water reaches taps at no more than 50°C (Business Queensland, Hot water systems). Lowering the thermostat below 60°C to prevent scalding is not advisable, as the temperature control device is specifically designed to prevent this issue.

An incorrectly adjusted temperature control device can also result in showers feeling cooler than expected. A licensed plumber can check both the tank thermostat and tempering valve to ensure they are properly calibrated in accordance with Queensland regulations.

5. Is Your Solar Hot Water System Getting Enough Sunlight or Is the Booster Not Working?

If you own a solar hot water system and notice a drop in performance, this is usually linked to either weather conditions or the functionality of the booster. The system depends on its electric or gas booster during cloudy or rainy days, as well as in winter when sunlight is less intense.

Key indicators of issues with a solar hot water system:

• The shortage coincides with periods of overcast or rainy weather.
• The booster switch is turned off, or the booster fails to activate as intended.
• The controller shows a fault indicator or error message.

Our guide to solar hot water boosters in Queensland elaborates on how the booster operates and clarifies why every solar system requires one.

6. Are Off-Peak Tariffs Restricting Your Electric Hot Water System’s Reheating Capability?

Many households in Queensland use electric hot water systems on Tariff 31 or Tariff 33. These tariffs offer reduced rates because the network powers the hot water circuit only during certain times. If your household uses more hot water than the tank can replenish between these intervals, it will deplete and remain cold until power is restored.

Indicators that tariff restrictions may be the issue:

• Hot water runs low in the evening but is available again the next morning.
• Your electricity bill includes a separate entry for a controlled load, specifically Tariff 31 or Tariff 33.
• Additional guests or more laundry loads have pushed the tank to its limits.

Energy Matters notes that the second controlled load option is slightly more expensive than the first but provides power for a longer duration, often covering part of the day (Energy Matters, Controlled Load Tariff Explained). Your options include upgrading to a larger tank, switching to a tariff with longer supply hours, or choosing a different type of system. Your electricity retailer can confirm your current tariff.

7. Is Your Hot Water System Approaching the End of Its Lifespan?

As hot water storage tanks age, they often lose capacity due to sediment build-up and wear on components. If your hot water supply is diminishing and the tank shows signs of rust, leaks around the base, or increasing noise levels each year, replacing the system may be more practical than ongoing repairs.

Our article on the lifespan of hot water systems provides a comprehensive overview of the expected duration for each type, while our guide on leaks from the bottom of a water heater explains what a leak around the tank’s base generally signifies.

Essential Checks Before Contacting a Plumber About Hot Water Shortages

A few straightforward checks can help identify the cause of hot water shortages and assist your plumber in diagnosing the issue. None of these steps require you to open the hot water system.

• Track when the hot water runs out: Is it only in the evening, after a specific number of showers, or is it a constant problem?
• Review your electricity bill for any mention of a controlled load, Tariff 31, or Tariff 33.
• Inspect the base of the tank and the relief valve pipe for any signs of dripping or pooling water.
• Listen for rumbling or popping sounds while the tank heats up.
• If you have a solar system, confirm that the booster switch is on and that the controller indicates no faults.
• Find the brand, model, and installation date on the label affixed to the side of the tank.

Common Questions About Hot Water Shortages

How long does it take for hot water to return after running out?

The wait time varies based on the type of system. Electric tanks on a standard tariff and gas storage tanks begin reheating immediately. An electric tank on Tariff 31 or Tariff 33 only reheats when the network powers the circuit, which may leave it cold until the next off-peak period. If the water remains cold the next morning, it’s advisable to have the system inspected.

How can I tell if I need a larger hot water system or a new one?

If the issue arose when your household size increased and the system otherwise functions well, it likely indicates a need for a larger system. Conversely, if the problem has developed gradually in an older tank, or if the tank shows signs of rust, leaks, or unusual noises, replacement is probably the better option.

Is it possible to increase the size of my hot water tank?

While you cannot physically enlarge an existing hot water tank, you can replace it with a larger system. We assess the number of residents in the household, their hot water usage patterns, and the system’s energy source to recommend an appropriately sized tank and system type.

How long does it take to replace a hot water system?

Most hot water system replacements are completed within a single day, especially when the new system matches the type and size of the old one.

Trusted Hot Water Solutions in Caboolture, Morayfield, and Moreton Bay

Creek to Coast Plumbing has been proudly serving homes throughout Caboolture, Morayfield, and the Moreton Bay region since 2012. Our licensed plumbers and gas fitters specialise in the installation and servicing of electric, gas, solar, and heat pump hot water systems. We will identify the cause of your hot water shortages, clarify your options, and provide a quote before any work begins.

Contact us at 1300 793 962 or send a message to Damian or our team detailing your hot water issue and its occurrence. You can also learn more about our hot water services in Caboolture.