Running Out of Hot Water: Causes and Solutions

You may remember when a steady flow of hot water was always available, but now, you’re faced with sudden cold showers, or the last person to bathe is left with only a lukewarm trickle. If you notice that your hot water supply is dwindling faster than before, it indicates that something is not quite right. This issue could arise from changes in how your household uses hot water, problems within the hot water system itself, or issues with the energy source powering the system.

This detailed guide outlines seven prevalent reasons for hot water shortages in Queensland households. It also provides insights on how long you might expect to wait for hot water to return after it has run out, along with practical checks you can perform before calling 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 indicates a fault rather than high demand.
• Common factors contributing to 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 wait time for hot water to return 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, enabling quick reheating of the tank. Larger tanks paired with smaller elements may require more time to reach the desired 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 determines when power is supplied, meaning a tank that empties in the evening may not begin reheating until the next off-peak cycle.
• Gas storage tank: The burner ignites as soon as the water temperature falls, allowing for immediate reheating. If it fails to ignite, check the pilot light for any issues.
• Gas continuous flow: These systems heat water on demand, which eliminates the risk of running out. If the water turns cold, the issue likely lies with a fault, gas supply, or flow problem rather than a depletion of stored hot water.
• Solar hot water: Recovery depends on sunlight availability and the booster’s efficiency. After several overcast days, the booster usually takes on the majority of the load.

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 that operate on their own circuit, with power restricted to specific time slots, typically 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 consumption.

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

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

Hot water systems are typically sized to meet the demands of the households 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 needs of a family of four.

Signs that your hot water system may be too small:

• Hot water runs out after only one or two consecutive showers.
• The family must meticulously plan shower times to prevent the last person from facing cold water.
• The issue arose following an increase in household size rather than being a result of system age.

If your hot water system operates 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 regulate the heating cycle. If either of these components starts to fail, the water may not heat properly, resulting in the tank depleting quicker 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 examine both components and advise whether replacement is a feasible 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.
• Cloudy, gritty, or rusty water flowing from the taps.

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

4. Is Your Hot Water Thermostat Set Too Low?

Some people lower the thermostat setting to save 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 higher usage of the tank’s contents.

The Queensland Government recommends that stored hot water in homes should be heated to at least 60°C to prevent the growth of bacteria such as Legionella. New and replacement systems must be fitted with 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 for this purpose.

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 are calibrated in accordance with Queensland regulations.

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

If you have a solar hot water system and notice a drop in performance, this is often related to weather conditions or the booster’s operation. 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 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 explains why every solar system requires one.

6. Do Tariff Restrictions Affect When Your Electric Hot Water System Can Reheat?

Many households in Queensland use electric hot water systems on Tariff 31 or Tariff 33. These tariffs provide reduced rates because the network only powers the hot water circuit during specific times. If your household uses 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 causing the problem:

• 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.
• Additional visitors or extra laundry loads have pushed the tank to its limits.

Energy Matters states 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 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 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 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 Engaging 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.

• Note when the hot water runs out: Is it only in the evenings, after a specific number of showers, or is it a recurring issue?
• Review your electricity bill for any mention of a controlled load, Tariff 31, or Tariff 33.
• Examine 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 turned on and that the controller shows no faults.
• Locate the brand, model, and installation date on the label affixed to the side of the tank.

Common Inquiries About Hot Water Shortages

What Is the 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 may 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 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 is likely the better option.

Can I 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, 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 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, 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.