Hot Water Issues: Understanding Causes and Solutions

Previously, you may have relished a steady flow of hot water. Now, however, you might find your shower turning unexpectedly cold, or the last person to bathe is left with only a lukewarm trickle. If your hot water supply is diminishing faster than it used to, this is a strong indicator that something is wrong. This issue could stem from changes in how your household uses water, complications within the hot water system, or even problems with the energy source that powers the system.

This comprehensive guide delves into seven common reasons for hot water shortages in homes across Queensland. It also provides insights on how long you can expect to wait for hot water to return after it runs out, along with practical checks you can carry out before calling a plumber.

Explore the Main Causes of Hot Water Shortages

• An electric tank operating on an off-peak (controlled load) tariff heats water only when the electricity network activates the power supply. If this occurs, the tank may remain cold until the next scheduled off-peak period.
• If you find the water remains cold the following morning, this suggests a malfunction rather than simply high demand.
• Common culprits for hot water shortages include a tank that is too small for your household’s needs, a faulty heating element or thermostat, sediment accumulation, a thermostat set too low, inadequate solar boosting, tariff restrictions, or an ageing system.

What Is the Anticipated Wait Time for Hot Water to Reappear After Depletion?

The time you need to wait mainly 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 as soon as the water temperature drops, allowing for quick 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 such as Tariff 31 or Tariff 33 dictate when power is supplied. If your tank depletes in the evening, it might not start reheating until the next off-peak cycle.
• Gas storage tank: The burner ignites whenever the water temperature decreases, allowing for 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 problem likely lies with a fault, gas supply, or flow issue rather than a lack of stored hot water.
• Solar hot water: Recovery is contingent on sunlight availability and the efficiency of the booster. After several cloudy days, the booster typically assumes the majority of the workload.

As highlighted by Energy Made Easy, the Australian Government’s energy comparison service, a controlled load tariff is designated for 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 indicates that the tank has not reheated, suggesting a fault rather than excessive use.

If you have a gas hot water system and are facing a shortage, our guide on pilot light issues can assist you in performing the necessary preliminary checks.

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

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

Signs that your hot water system may be undersized include:

• Hot water runs out after just one or two consecutive showers.
• The family has to coordinate shower times to ensure the last person does not receive cold water.
• The problem arose after an increase in household size, not simply due to the system’s age.

If your hot water system is functioning correctly but lacks the necessary capacity, upgrading to a larger tank or a different type of system will resolve the issue. 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 Issues 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 not heat adequately or 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 feasible based on the tank’s age. Schedule an inspection of your hot water system if you notice any of these signs.

3. Has Sediment Accumulated 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, impeding the heating process.

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

• Rumbling or popping sounds emanating from the tank during heating.
• Hot water depletes faster without any 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 affects a tank’s longevity.

4. Is Your Hot Water Thermostat Set Too Low?

Some individuals 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, resulting in increased consumption of the tank’s contents.

The Queensland Government recommends that stored hot water in homes be heated to a minimum of 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 the water delivered to taps does not exceed 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 incorrectly adjusted temperature control device can also lead to showers feeling cooler than expected. A licensed plumber can evaluate both the tank thermostat and tempering valve to ensure they are calibrated according to Queensland regulations.

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

If you own a solar hot water system and have noticed a decline in performance, this is often linked to 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 include:

• The shortage coincides with a period of overcast or rainy weather.
• The booster switch is off, or the booster fails to activate as needed.
• The controller displays 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. Are Off-Peak Tariff Restrictions Affecting Your Electric Hot Water System’s Reheating?

Many households in Queensland utilise 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 consumes more hot water than the tank can replenish during these intervals, it will run out and stay 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 features 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 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 Nearing 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 over the years, replacing the system may 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.

Essential Checks to Conduct Before Contacting a Plumber Regarding Hot Water Shortages

A few straightforward checks can help pinpoint 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?
• 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.

Frequently Asked 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 is 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.

Professional 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.