Your water may not be getting hot due to an issue with your water heater's power supply, a tripped reset switch, a broken heating component, or heavy sediment buildup.
To fix water that isn't getting hot, first check your circuit breaker to ensure the water heater hasn't tripped. If power is on, reset the water heater’s safety limit switch, check that gas pilot lights are active (if applicable), or adjust the thermostat to 120∘F120 raised to the composed with power cap F120∘𝐹.
A sudden loss of hot water usually means your water heater has stopped heating or there is a plumbing crossover. Common culprits include a tripped circuit breaker, an extinguished pilot light, or a failed heating element.
To reset an electric water heater, turn off its dedicated circuit breaker. Remove the upper access panel and pull back the insulation to reveal the red safety reset button. Firmly press the button until you hear a click, replace the panel, and turn the breaker back on.
No hot water is usually caused by a tripped circuit breaker, an extinguished pilot light, a malfunctioning thermostat, or heavy sediment buildup in your tank.
Clearing a hot water pipe blockage typically involves cleaning the faucet aerator, back-flushing the supply lines to remove mineral sediment, or thawing frozen pipes. Start with the most common and accessible fixes:
Signs a Water Heater is Going Bad
The reset button's location depends on your thermostat type. For older models, it is usually a recessed button on the circuit board (often behind the faceplate) or a dedicated button on the front or side. For modern smart thermostats, you typically reset the device through the digital menu.
A water heater's reset button takes only a few seconds to press, but the unit will take 1 to 2 hours to fully reheat a tank of cold water. For normal "recovery" between uses, it takes about 30 to 60 minutes for water to heat up.
If you suddenly have no hot water, the very first step is to isolate whether the issue is with a single faucet or your entire home. If it affects the whole house, your water heater is the culprit, and you should check the following based on your system:
When you have cold water but no hot water, the issue almost always stems from the water heater or a plumbing crossover, rather than the faucets themselves.
A tap or shower that keeps switching between hot and cold water could be a sign that the heat exchanger inside a combi boiler is blocked. Sludge and sediment buildup is fairly common in older boilers, especially when the filters are old. This blockage will then cause water to run hot and cold intermittently.
A bad thermostat—whether in your vehicle or your home’s HVAC system—fails to regulate temperature. In cars, it causes engine overheating or poor fuel efficiency. In homes, it leads to unresponsive systems, short cycling (turning on and off rapidly), or incorrect temperature readings.
If you are experiencing lukewarm water from your hot taps but your radiators heat up fine, or vice versa, the diverter valve is the likely culprit. You should not attempt to fix the issue yourself, but rather enlist the help of a qualified engineer who can advise you on whether it needs to be cleaned or replaced.
Pushing the reset button on a thermostat clears errors and restores communication with your HVAC unit. However, depending on the type of reset, it will usually erase all custom schedules, temperature settings, and Wi-Fi configurations.
Why you might need to reset/reboot your HVAC thermostat
Resetting can recalibrate the temperature sensor. Failure to Turn On HVAC System: A thermostat reset reboots its system and attempts to restart normal functioning. This resolves problems where it fails to turn on your AC, heat, or fan.
Symptoms of a bad water heater thermostat include inconsistent water temperatures (fluctuating between hot and cold), water that is scalding hot, completely cold water, or unusually high electric bills. You may also notice the unit running constantly or hear unusual popping/banging noises.
A manual thermostat replacement cost is usually between £110 and £140, including labour and materials. However, you may want to consider upgrading to a programmable or smart thermostat, which can offer you more convenience, comfort, and energy savings.
Common Causes of Water Heater Failure
Traditional tank water heaters last 8 to 12 years, while tankless models typically last 15 to 20 years. Lifespans vary greatly depending on water quality, unit design, and whether you perform regular maintenance like flushing the tank and checking the anode rod.
Electric vs. Gas Safety Limits: With electric water heaters, minor external leaks may allow brief continued use, provided water isn't contacting any electrical components. For gas heaters, any gas smell or pilot light issues demand immediate shutdown and professional assessment.