Running Out of Hot Water: Causes and Solutions Explained

In the past, you may have enjoyed a plentiful supply of hot water, but now you find your shower turning cold unexpectedly, or the last person to bathe is left with only a tepid trickle. If your access to hot water is diminishing more quickly than before, it is a clear indication that something is amiss. This issue could arise from changes in household usage patterns, complications within the hot water system itself, or even the energy source that powers the system.

This detailed guide explores seven prevalent reasons for hot water shortages in Queensland homes. it provides insights on the expected wait time for hot water to return after it has been exhausted, along with practical checks you can perform before contacting a plumber.

Identifying Key Reasons Behind Hot Water Shortages

• An electric tank operating on an off-peak (controlled load) tariff heats only when the electricity network activates its power supply, potentially leaving it cold until the next scheduled off-peak period.
• If the water remains cold the following morning, it indicates a malfunction rather than simply high demand.
• Frequent causes of hot water shortages include a tank that fails to meet the household’s requirements, a defective heating element or thermostat, sediment build-up, a thermostat set too low, insufficient solar boosting, tariff restrictions, or an ageing system.

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

The wait time largely depends 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 prompt reheating of the tank. Larger tanks with smaller elements may take longer to reach the desired temperature.
• Electric storage tank on an off-peak tariff: In Queensland, controlled load tariffs are known as Tariff 31 or Tariff 33. Your electricity provider determines when power is supplied, meaning a tank that depletes in the evening might not start reheating until the next off-peak cycle.
• Gas storage tank: The burner ignites whenever the water temperature drops, enabling immediate reheating of the tank. If it fails to ignite, check for issues with the pilot light.
• 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 issue rather than a lack of stored hot water.
• Solar hot water: Recovery depends on sunlight availability and the efficiency of the booster. After several overcast days, the booster generally takes on most of the workload.

As noted by Energy Made Easy, the Australian Government’s energy comparison service, a controlled load tariff is assigned to larger appliances like hot water systems that operate on their own circuit, with power limited 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, it suggests that the tank has not reheated, indicating a fault rather than excessive use.

For those using gas hot water systems and experiencing a shortage of hot water, our guide on pilot light issues can support you in conducting the necessary preliminary checks.

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

Hot water systems are typically sized to meet the needs of the household they serve. As families expand, teenagers take longer showers, and remote work increases daytime water consumption, a system designed for two may struggle to cater to 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 coordinate shower times to prevent the last person from getting cold water.
• The issue arose after an increase in household size, not as the system aged.

If your hot water system is functioning correctly yet simply lacks the required capacity, upgrading to a larger tank or a different type of system will resolve the problem. Our guide to various hot water systems suitable for Brisbane and Moreton Bay homes compares options including 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 component begins to fail, the water may heat inadequately or not at all, causing the tank to deplete more quickly than before.

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 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 operate on mains power. Avoid attempting to open this cover yourself. A qualified plumber can inspect 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 the storage tank. This sediment layer occupies space that should be filled with hot water, and in electric tanks, it can insulate the heating element, hindering the heating process.

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

• Rumbling or popping sounds coming from the tank during heating.
• Hot water depletes faster without changes in consumption.
• Cloudy, gritty, or rusty water flowing from the taps.

During a service visit, a plumber will flush the sediment from the tank and check the sacrificial anode, a rod inside the tank designed to corrode and protect the tank from damage. Our article on hard water and hot water systems in Caboolture discusses how water quality impacts a tank’s longevity.

4. Is Your Hot Water Thermostat Set Too Low?

Some individuals lower the thermostat setting to conserve energy or to avoid 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, leading to increased consumption of the tank’s contents.

The Queensland Government recommends that stored hot water in homes must be heated to a minimum of 60°C to prevent the growth of bacteria such as Legionella. New and replacement systems are required to be fitted with a temperature control device to ensure that water delivered to taps does not exceed 50°C (Business Queensland, Hot water systems). Reducing the thermostat below 60°C to avoid scalding is not advisable, as the temperature control device is specifically designed for this purpose.

An incorrectly adjusted temperature control device can also lead to showers feeling cooler than expected. A licensed plumber can assess both the tank thermostat and tempering valve to ensure they are calibrated according to Queensland regulations.

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

If you own a solar hot water system and notice a decline in performance, this is often related to weather conditions or the booster’s functionality. 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 problems with a solar hot water system include:

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

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

6. Does Your Off-Peak Tariff Restrict When Your Electric Hot Water System Can Reheat?

Numerous households in Queensland utilise electric hot water systems on Tariff 31 or Tariff 33. These tariffs offer reduced rates because the network only powers the hot water circuit during specific times. If your household consumes more hot water than the tank can replenish during these intervals, it will run out and remain cold until power is restored.

Signs that tariff restrictions may be the issue include:

• Hot water runs short 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 extra laundry loads have pushed the tank to its limits.

Energy Matters highlights 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 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 diminishing and the tank shows signs of rust, leaks around the base, or increasing noise levels annually, replacing the system can be more practical than ongoing repairs.

Our article on the lifespan of hot water systems provides a detailed 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.

Practical Checks to Perform Before Contacting a Plumber About Hot Water Shortages

A few simple checks can help identify the cause of hot water shortages and assist your plumber in diagnosing the problem. 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 specific number of showers, or is it a consistent issue?
• Check 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 any rumbling or popping sounds during the heating process.
• If you have a solar system, ensure that the booster switch is on and that the controller indicates no faults.
• Locate 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 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 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 determine if I need a larger hot water system or a new one?

If the issue arose with an increase in household size 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 may be 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 evaluate 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, particularly 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 served 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, explain 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 when it occurs. You can also learn more about our hot water services in Caboolture.