Running out of Hot Water: Causes and Solutions Explained

Previously, you enjoyed a steady supply of hot water, but now your shower may suddenly turn cold, or the last person to bathe only experiences a lukewarm trickle. If you notice that your access to hot water is diminishing more quickly than before, it indicates that something is not right. This issue could arise from changes in how your household uses hot water, faults within the hot water system itself, or even problems with the energy source that powers your system.

This comprehensive guide outlines seven prevalent reasons for hot water shortages in Queensland homes. It also provides insights on how long you should expect to wait for hot water to be restored after it has run out, alongside practical checks you can conduct before contacting a plumber.

Identifying the Main Factors Behind 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 can leave it cold until the next scheduled off-peak period.
• If the water remains cold the following morning, this suggests a malfunction rather than high demand.
• Common issues leading to hot water shortages include a tank that lacks capacity for the household’s needs, a faulty heating element or thermostat, sediment build-up, a thermostat set too low, inadequate solar boosting, tariff restrictions, or an ageing system.

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

The waiting time is primarily dependent 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 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 might not resume reheating until the next off-peak cycle.
• Gas storage tank: the burner ignites whenever the water temperature decreases, enabling instant reheating of the tank. If this doesn’t happen, check the pilot light for any issues.
• Gas continuous flow: these systems heat water on demand, eliminating the risk of running out. If the water turns cold, the issue is likely related to 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 efficiency of the booster. After several cloudy days, the booster typically handles most 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, usually overnight and on weekends (Energy Made Easy, Understanding controlled loads). If your hot water remains cold the next morning following an off-peak period, it indicates that the tank has not reheated, suggesting a fault rather than excessive consumption.

If you are using gas hot water systems and experiencing a hot water shortage, our guide on pilot light issues can assist you with initial checks.

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

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

Indicators that your hot water system might be undersized:

• Hot water runs out after just one or two consecutive showers.
• The family must carefully coordinate shower times to avoid leaving the last person with cold water.
• The issue arose after an increase in household size, rather than as the system aged.

If your hot water system functions correctly but lacks adequate capacity, upgrading to a larger tank or a different system type will resolve your issues. 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 component starts to fail, the water may heat inadequately or not at all, leading to quicker depletion of the tank’s contents.

Indicators of a failing heating element or thermostat:

• The water is warm but fails to 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 examine both components and advise whether replacement is a viable option based on the tank’s age. Schedule an inspection of your hot water system if you notice any of these symptoms.

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 in electric tanks, it can coat the heating element, impairing 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 unchanged consumption patterns.
• 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 deterioration. Our article on hard water and hot water systems in Caboolture explores how water quality impacts a tank’s lifespan.

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. cooler water in the tank depletes more quickly, as less cold water mixes during showers, resulting in greater consumption of the tank’s contents.

The Queensland Government recommends that stored hot water in homes should 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 inadvisable, as the temperature control device is specifically designed for this purpose.

An incorrectly adjusted temperature control device can also result in showers feeling cooler than expected. A licensed plumber can check both the tank thermostat and tempering valve to ensure they are calibrated in line with Queensland regulations.

5. Is Your Solar Hot Water System Getting Enough Sunlight or Is the Booster Not Functioning?

If you own a solar hot water system and are noticing a drop in performance, this is usually related to either the weather conditions or the booster’s effectiveness. 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 that indicate issues with a solar hot water system:

• 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 explains how the booster functions and clarifies why every solar system needs one.

6. Is Your Off-Peak Tariff Restricting When Your Electric Hot Water System Can Reheat?

Many households in Queensland utilise electric hot water systems on Tariff 31 or Tariff 33. These tariffs offer reduced rates since 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 might be the cause:

• 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 system type. 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 each year, replacing the system may be more cost-effective than continual repairs.

Our article on the lifespan of hot water systems provides 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 About Hot Water Shortages

A few straightforward 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 consistent issue?
• Examine your electricity bill for mentions 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 heating.
• If you have a solar system, confirm that the booster switch is turned on and that the controller indicates no faults.
• Note the brand, model, and installation date on the label affixed to the side of the tank.

Frequently Asked Questions Regarding Hot Water Shortages

What is the typical wait time for hot water to return after it has run 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 altogether?

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.

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 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.

What is the typical time frame 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 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 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.