Running out of Hot Water: Causes and Effective Solutions

Once upon a time, you enjoyed an endless supply of hot water, but now you find your shower turning cold unexpectedly, or the last person to bathe is left with a mere lukewarm trickle. Noticing that your access to hot water is diminishing more rapidly than before indicates that something is amiss. This issue may arise from changes in your household’s usage habits, complications within the hot water system itself, or even the energy source that powers it.

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

Essential Factors Leading to Hot Water Shortages

• An electric tank running on an off-peak (controlled load) tariff only heats water when the electricity network activates its supply, which may leave it cold until the next designated off-peak cycle.
• If the water remains cold the following morning, it indicates a malfunction rather than high demand.
• Common reasons for hot water shortages include a tank that is inadequate for the household’s requirements, 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 time you should wait 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 quick reheating of the tank. Larger tanks with smaller elements may take longer to achieve 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 as soon as the water temperature falls, permitting instant reheating of the tank. If it fails to do so, inspect the pilot light for any issues.
• Gas continuous flow: these systems heat water on demand, eliminating the possibility of running out. If the water turns cold, the issue likely lies with a fault, gas supply, or flow issue rather than a 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 the majority 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 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 suggests that the tank has not reheated, indicating a fault rather than excessive consumption.

For those using gas hot water systems that are experiencing shortages, our guide on pilot light issues can assist you in performing 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 grow, teenagers take longer showers, and remote work increases daytime usage, a system designed for two individuals may find it challenging to meet the demands 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 must carefully schedule shower timings to prevent the last person ending up with cold water.
• The issue emerged following an increase in household size, rather than as the system aged.

If your hot water system is functioning correctly but 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 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 depends on its heating element to warm the water and its thermostat to regulate the heating cycle. If either of these components begins to fail, the water may heat inadequately or not at all, causing the tank to deplete more quickly than it should.

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 assess 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 symptoms.

3. Has Sediment Accumulated in Your Hot Water Tank?

Over time, minerals present 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, hindering the heating process.

Indicators 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 consumption patterns.
• Cloudy, gritty, or rusty water emerging from the taps.

During a service visit, a plumber will flush the sediment from the tank and inspect 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 explores how water quality affects a tank’s longevity.

4. Is Your Hot Water Thermostat Set at an Inadequate Temperature?

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 greater 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 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 unwise, as the temperature control device is specifically designed for this purpose.

An improperly adjusted temperature control device can also result in showers feeling cooler than expected. A licensed plumber can examine both the tank thermostat and tempering valve to ensure they are calibrated in accordance with 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 notice a decline in performance, this is generally linked to either weather conditions or the functionality of the booster. 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 signs indicating issues 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 intended.
• The controller displays 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. Are Tariff Restrictions Affecting Your Electric Hot Water System’s Reheating Schedule?

Many 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 between 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 following morning.
• Your electricity bill includes a separate entry for a controlled load, specifically Tariff 31 or Tariff 33.
• Extra guests or additional 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 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 continually repairing it.

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 Before Contacting a Plumber Regarding 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 certain number of showers, or is it a persistent 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 turned 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 Regarding Hot Water Shortages

What is the typical wait time for hot water to return after it runs 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 ascertain whether 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 more sensible option.

Is it feasible 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.

What is the typical duration for replacing 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 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.