Running Out of Hot Water: Causes and Fixes

Once, you enjoyed an ample supply of hot water, but now your shower turns cold unexpectedly, leaving the last person with only a lukewarm trickle. If you notice that your access to hot water is running out faster than it used to, it indicates that something has changed. This issue may arise from shifts in household usage, problems within the hot water system itself, or the energy source powering the system.

This detailed guide outlines seven common reasons for hot water shortages in Queensland homes. It also provides insights into how long you can expect to wait for hot water to return after it has been depleted and includes practical checks you can perform before contacting a plumber.

Understanding the Main Causes of Hot Water Shortages

• An electric tank that operates on an off-peak (controlled load) tariff heats up only when the electricity network activates its power supply, which may leave it cold until the next scheduled off-peak period.
• If the water remains cold the following morning, it suggests a malfunction rather than high demand.
• Common factors leading to hot water shortages include a tank that is inadequate for the household’s needs, a faulty 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 Waiting Time for Hot Water to Return After Depletion?

The waiting time primarily 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 quick reheating of the tank. Larger tanks with smaller elements may take longer to reach the optimal temperature.
• Electric storage tank on an off-peak tariff: In Queensland, these controlled load tariffs are known as Tariff 31 or Tariff 33. Your electricity provider dictates 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, allowing for immediate reheating. If it fails to ignite, check the pilot light for issues.
• Gas continuous flow: These systems heat water on demand, eliminating the risk of running out. If the water turns cold, the issue likely stems from a fault, gas supply, or flow problem rather than depletion of stored hot water.
• Solar hot water: Recovery depends on sunlight availability and the efficiency of the booster. 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 is applied to larger appliances like hot water systems operating on their own circuit, with power restricted 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 consumption.

For those using gas hot water systems and facing hot water shortages, our guide on pilot light issues can assist you in performing the necessary initial checks.

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

Hot water systems are typically sized to meet the needs of the household they serve. As families grow, teenagers take longer showers, and remote work increases daytime usage, a system designed for two people may struggle to accommodate the demands of a family of four.

Signs that your hot water system may be too small:

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

If your hot water system operates correctly but simply lacks the needed capacity, upgrading to a larger tank or a different type of system will rectify the issue. 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 starts to fail, the water may not heat adequately or may not heat at all, leading to the tank depleting more quickly 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 operate 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 Inside Your Hot Water Tank?

Over time, minerals in the water settle at the bottom of a storage tank. This sediment layer takes up space that should be occupied by hot water and, in electric tanks, can coat the heating element, reducing its effectiveness.

Signs of sediment accumulation in the hot water tank:

• Rumbling or popping sounds 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 check 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 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 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, leading to greater consumption of the tank’s contents.

The Queensland Government advises that stored hot water must 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 avoid scalding is not advisable, as the temperature control device is specifically designed for this purpose.

An improperly adjusted temperature control device can also lead to showers feeling cooler than expected. A licensed plumber can check 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 reduction in performance, this is usually linked to 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 problems with a solar hot water system:

• The shortage coincides with a period of overcast or rainy weather.
• The booster switch is off, or the booster doesn’t activate as intended.
• The controller shows a fault indicator or error message.

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

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

Many households in Queensland use 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 between these intervals, it will run out and remain cold until power is restored.

Indicators that tariff restrictions may be the issue:

• Hot water runs short in the evening but is available again the following morning.
• Your electricity bill includes a separate entry for a controlled load, specifically Tariff 31 or Tariff 33.
• Extra guests or increased 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 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 Useful Life?

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 over time, replacing the system may be more practical than continuously repairing it.

Our article on the lifespan of hot water systems offers a detailed overview of the expected 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 typically indicates.

Essential Checks Before Calling a Plumber Regarding 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.

• 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?
• Examine 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 while the tank heats.
• If you have a solar system, ensure that the booster switch is 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 Regarding Hot Water Shortages

How long does it typically 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.

What signs indicate that I need a larger hot water system or a new one?

If the issue arose when your household size increased and the system otherwise operates 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 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 served households 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 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.