Running out of Hot Water? Seven Causes and Solutions

You used to enjoy an abundance of hot water, but now you find the shower turning cold midway through, or the last person to use it is left with only a lukewarm trickle. When you notice that your hot water runs out more quickly than it once did, something has changed. This could be related to the household dynamics, an issue within the hot water system itself, or the method by which the system is powered.

This guide outlines seven prevalent reasons for a shortage of hot water in Queensland homes. It also provides insight into the expected wait time for hot water to return after depletion, along with some checks you can perform before contacting a plumber.

Essential Insights on Hot Water Shortages

• An electric tank operating on an off-peak (controlled load) tariff only reheats when the electricity network activates its power, meaning it may remain cold until the next off-peak interval.
• If water remains cold the following morning, it indicates a fault, not heavy usage.
• Common culprits include a tank that is too small for the household’s needs, a malfunctioning heating element or thermostat, sediment buildup, a low thermostat setting, an insufficient solar booster, tariff limitations, or an ageing system.

What Is the Wait Time for Hot Water to Return After Running Out?

The time you should wait depends largely on the type of hot water system you have and its power source.

• Electric storage tank on a standard tariff: the heating element activates immediately when the water temperature decreases, allowing the tank to start reheating right away. larger tanks with smaller elements may take longer to recover.
• 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 network determines when power is supplied, so a tank that runs out in the evening may not start reheating until the next off-peak period.
• Gas storage tank: the burner ignites whenever the water temperature drops, leading to immediate reheating of the tank. If it fails to return, check the pilot light.
• Gas continuous flow: these systems heat water on demand, without a tank to deplete. If the water turns cold, the issue lies with a fault, gas supply, or flow problem, rather than a lack of stored hot water.
• Solar hot water: recovery relies on sunlight and the efficiency of the booster. After several cloudy days, the booster typically does most of the work.

According to Energy Made Easy, the Australian Government’s energy comparison service, a controlled load tariff applies to larger appliances like hot water systems that operate on their own circuit, with power restricted to specific periods, 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 the tank has not reheated, indicating a fault rather than excessive use.

For those with gas hot water systems who experience a lack of hot water, our guide on gas hot water pilot light issues can help you identify the initial checks to perform.

1. Is Your Hot Water System Inadequate for Your Household Size?

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

Indicators that your hot water system is too small:

• Hot water runs out after just one or two consecutive showers.
• The family coordinates showers strategically to prevent the last person from experiencing cold water.
• The issue began when the household size increased, rather than as the system aged.

If your hot water system is functioning correctly but simply lacks capacity, upgrading to a larger tank or a different type of system will resolve the issue. Our guide to the various hot water systems suitable for Brisbane and Moreton Bay homes compares options such as electric, gas, solar, and heat pump systems.

2. Are You Experiencing Issues 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 component begins to fail, the water may only heat partially or not at all, causing the tank to deplete faster than before.

Signs of a failing heating element or thermostat:

• The water is warm but never reaches a proper hot temperature.
• Hot water runs out significantly sooner than it did a few months back.
• The safety switch trips when the hot water system is powered on.

Both the element and thermostat are located behind a cover on the tank and operate on mains power. Do not attempt to open the cover yourself. A licensed plumber can assess both components and advise whether replacing them is a viable option based on the tank's age. Schedule a hot water system inspection if you notice any of these symptoms.

3. Has Sediment Accumulated Inside 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, slowing down the heating process.

Indicators of sediment buildup in the hot water tank:

• Rumbling or popping sounds emanating from the tank during heating.
• Hot water depletes faster despite no changes in usage patterns.
• Cloudy, gritty, or rusty water appearing at 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, protecting the tank itself from deterioration. Our article on hard water and hot water systems in Caboolture discusses how water quality influences the longevity of a tank.

4. Is Your Hot Water Thermostat Set Too Low?

Some individuals lower the thermostat to conserve energy or to prevent excessively hot water at the taps. The downside is that cooler water in the tank runs out quicker, as less cold water is mixed during showers, leading to greater consumption of the tank’s contents.

The Queensland Government advises that stored hot water in homes must be heated to at least 60°C to inhibit the growth of bacteria like Legionella. new and replacement systems must be fitted with a temperature control device to ensure water reaches taps at no more than 50°C (Business Queensland, Hot water systems). Reducing the tank thermostat below 60°C to avoid scalding is not a suitable solution since the temperature control device is specifically designed for that purpose.

An incorrectly adjusted temperature control device can also lead to showers feeling cooler than expected. A licensed plumber can examine the tank thermostat and tempering valve together, ensuring both are calibrated to comply with Queensland regulations.

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

If you have a solar hot water system and start noticing a shortage, it is usually related to either the weather or the booster. This system relies on its electric or gas booster during cloudy and rainy days, as well as in winter when sunlight is less intense.

Key indicators of issues with a solar hot water system:

• The shortage coincided with a period of cloudy or rainy weather.
• The booster switch is turned off, or the booster fails to activate.
• The controller displays a fault indicator or error code.

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

6. Does Your Off-Peak Tariff Restrict When Your Electric Hot Water System Can Reheat?

Many Queensland households utilise electric hot water systems on Tariff 31 or Tariff 33. These tariffs offer lower rates because the network only powers the hot water circuit during specific periods. If your household consumes more hot water than the tank can supply between these intervals, it will run out and remain cold until power is restored.

Signs indicating tariff limitations are 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, Tariff 31 or Tariff 33.
• Extra guests or additional loads of laundry have pushed the tank's 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 extended supply hours, or choosing 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 tend to lose capacity due to sediment accumulation and component wear. If your hot water supply is dwindling and the tank exhibits signs of rust, leakage around the base, or increasing noise each year, replacing the system often becomes more practical than continually installing new parts.

Our article on the lifespan of hot water systems provides a breakdown of the typical duration for each type, while our guide on leaks from the bottom of a water heater explains what a leak around the tank’s base typically signifies.

Simple 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 as well. None of these steps require you to open the hot water system.

• Observe when the hot water runs out: Is it in the evening only, after a certain number of showers, or is it a constant issue?
• Review 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 the controller indicates no faults.
• Locate the brand, model, and installation date on the label affixed to the side of the tank.

Common 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 initiate 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 determine 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 displays rust, leaks, or unusual noises, replacement is likely 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 assess the number of residents in the household, their hot water usage patterns, and the system's power 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 the same 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 homes throughout Caboolture, Morayfield, and the Moreton Bay region since 2012. Our licensed plumbers and gas fitters specialise in installing and servicing 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 the hot water issue and when it occurs. You can also explore more about our hot water services in Caboolture.