Running Out of Hot Water: Causes and Solutions Explained

Once, you enjoyed an endless supply of hot water, but now your shower turns cold without warning, leaving the last bather with only a lukewarm trickle. If you’re noticing that your access to hot water is diminishing more quickly than before, it indicates that something is amiss. This issue could arise from changes in household consumption, problems within the hot water system itself, or the energy source that fuels the system.

This detailed guide outlines seven prevalent reasons for hot water shortages in Queensland homes. It also provides insights on how long you should expect to wait for hot water to return after it has been used up, along with practical checks you can carry out before contacting a plumber.

Primary Reasons for Hot Water Shortages in Queensland Homes

• An electric tank operating on an off-peak (controlled load) tariff heats up only when the electricity network activates the power supply, which could leave it cold until the next scheduled off-peak period.
• If the water remains cold the next morning, it points to a malfunction rather than high demand.
• Typical causes of 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 Wait Time for Hot Water to Return After Depletion?

The time you need to wait depends significantly on the type of hot water system you have and its energy source.

• Electric storage tank on a standard tariff: The heating element activates immediately when the water temperature drops, allowing for quick reheating of the tank. Larger tanks with smaller heating elements may take longer to reach the desired temperature.
• Electric storage tank on an off-peak tariff: In Queensland, these controlled load tariffs are referred to as Tariff 31 or Tariff 33. Your electricity provider determines when power is supplied, meaning a tank that empties in the evening may not start reheating until the next off-peak cycle.
• Gas storage tank: The burner ignites whenever the water temperature decreases, facilitating immediate reheating of the tank. If it fails to ignite, check the pilot light for any issues.
• Gas continuous flow: These systems heat water on demand, eliminating the risk of running out. If the water turns cold, the issue is likely related to a fault, gas supply, or flow issue rather than a lack of stored hot water.
• <a href="https://writebuff.com/heat-pumps-vs-solar-hot-water-which-is-superior/">Solar hot water:</a> Recovery time depends on sunlight availability and the booster’s efficiency. After several overcast days, the booster typically takes on most of the workload.

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

For those with gas hot water systems facing a lack of hot water, our guide on pilot light issues can help you perform the necessary initial checks.

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

Hot water systems are typically sized to accommodate the household they serve. As families expand, teenagers extend their showers, and working from home increases daytime usage, a system designed for two people may struggle to meet the demands of a family of four.

Indicators that your hot water system may be undersized include:

• Hot water runs out after just one or two consecutive showers.
• The family must carefully coordinate shower times to prevent the last person from having cold water.
• The issue arose after an increase in household size, rather than as the system aged.

If your hot water system functions correctly but lacks the necessary 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 control the heating cycle. If either component begins to fail, the water may heat inadequately or not at all, leading to a faster depletion of the tank’s contents.

Signs of a failing heating element or thermostat include:

• The water is warm but does not reach the desired hot temperature.
• Hot water runs out noticeably sooner than it did a few months prior.
• 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 operate on mains power. Avoid attempting to access this cover yourself. A qualified plumber can assess both components and determine whether replacement is a viable option based on the tank’s age. Schedule a hot water system inspection if you notice any of these symptoms.

3. Has Sediment Accumulated 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 in electric tanks, it can coat the heating element, obstructing the heating process.

Signs of sediment build-up in the hot water tank include:

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

During a service visit, a plumber will flush out the sediment from the tank and examine the sacrificial anode, a rod within 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 impacts a tank’s lifespan.

4. Is Your Hot Water Thermostat Set Too Low?

Some individuals lower the thermostat setting to save energy or to prevent excessively hot water at the taps. The downside is that cooler water in the tank depletes more quickly, as less cold water mixes during showers, resulting in greater consumption of the stored hot water.

The Queensland Government advises that stored hot water in homes must be heated to a minimum of 60°C to inhibit the growth of bacteria such as Legionella. New and replacement systems must feature 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 avoid scalding is not advisable, as the temperature control device is specifically designed to prevent this issue.

An improperly adjusted temperature control device can also cause showers to feel cooler than expected. A licensed plumber can check both the tank thermostat and tempering valve to ensure they comply with Queensland regulations.

5. Is Your Solar Hot Water System Receiving Enough Sunlight or Is the Booster Malfunctioning?

If you have a solar hot water system and experience a drop in performance, this is often linked to either weather conditions or the booster’s functionality. The system relies 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 include:

• The shortage coincides with a period of overcast or rainy weather.
• The booster switch is 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. Could Your Off-Peak Tariff Be Restricting Your Electric Hot Water System’s Reheating Times?

Many households in Queensland utilise 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 specific times. If your household consumes more hot water than the tank can replenish between these intervals, it will run out and remain cold until power is restored.

Signs that tariff restrictions may be causing the issue include:

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

Energy Matters notes that the second controlled load option is slightly pricier than the first but offers 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 extended supply hours, or selecting 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 dwindling and the tank exhibits signs of rust, leaks at 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 an overview of the typical duration for each type, while our guide on leaks from the bottom of a water heater clarifies what a leak around the tank’s base generally indicates.

Essential Checks Before You Contact a Plumber About Hot Water Shortages

Performing a few simple 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.

• Monitor when the hot water runs out: Is it only in the evening, after a certain number of showers, or is it a persistent issue?
• Review your electricity bill for mentions 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.
• If you have a solar system, ensure that the booster switch is turned on and that the controller shows no faults.
• Locate the brand, model, and installation date on the label attached to the side of the tank.

Common Questions About Hot Water Shortages

What is the typical wait time for hot water to return after running out?

The wait time varies depending on the system type. 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 could leave it cold until the next off-peak period. If the water remains cold the following 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 problem emerged when your household size increased and the system otherwise functions well, it likely indicates a need for a larger system. Conversely, if the issue has gradually developed in an older tank, or if the tank shows signs of rust, leaks, or unusual noises, a 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 your 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 typically 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.

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

Creek to Coast Plumbing has proudly provided services to homes across 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, explain your options, and provide a quote before any work commences.

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