Why is my water only warm instead of hot?
I can hear the cylinder heating when the immersion heater is turned on, but the water isnt hot, even if it has been on for a couple of hours
Hi Nikki
If your immersion heater is making its normal heating noises but the water is only ever warm, there are a few common causes.
The first thing to check is the immersion heater thermostat setting. Before removing any covers, switch off the power to the immersion heater at the fused spur or consumer unit and make sure the electricity is isolated. Remove the plastic thermostat cover (some require a screwdriver or pliers), and check the thermostat setting. Most have a dial marked with a + / – or a numbered scale. A typical hot water temperature is around 60°C. If it has been set too low, increase the setting, replace the cover, restore the power and allow the cylinder a couple of hours to reheat.
If the thermostat is already set correctly, the fault could be with the immersion heater itself. Heating elements can deteriorate with age, becoming less efficient or partially failing. In this case, the immersion heater may need replacing.
The type of hot water cylinder you have is also important. If you have an unvented hot water cylinder, another possibility is a faulty Temperature and Pressure Relief (T&P) Valve. This safety valve is designed to open only if the water overheats, normally at around 90–95°C. As these valves age, they can begin opening prematurely, allowing hot water to discharge into the drain before the cylinder reaches its normal operating temperature.
A simple check is to look at the tundish (the clear plastic fitting on the discharge pipe) after the immersion heater has been running for around an hour. If you can see a steady drip or continuous flow of water through the tundish, the T&P valve may be passing water and should be inspected and replaced by a G3-qualified engineer.
If there is no discharge from the tundish and the thermostat is correctly set, the next most likely causes are a faulty thermostat, a failing immersion heater, or, in systems with two immersion heaters, the wrong immersion heater being switched on.
Hi Nikki
If your immersion heater is making its normal heating noises but the water is only ever warm, there are a few common causes.
The first thing to check is the immersion heater thermostat setting. Before removing any covers, switch off the power to the immersion heater at the fused spur or consumer unit and make sure the electricity is isolated. Remove the plastic thermostat cover (some require a screwdriver or pliers), and check the thermostat setting. Most have a dial marked with a + / - or a numbered scale. A typical hot water temperature is around 60°C. If it has been set too low, increase the setting, replace the cover, restore the power and allow the cylinder a couple of hours to reheat.
If the thermostat is already set correctly, the fault could be with the immersion heater itself. Heating elements can deteriorate with age, becoming less efficient or partially failing. In this case, the immersion heater may need replacing.
The type of hot water cylinder you have is also important. If you have an unvented hot water cylinder, another possibility is a faulty Temperature and Pressure Relief (T&P) Valve. This safety valve is designed to open only if the water overheats, normally at around 90–95°C. As these valves age, they can begin opening prematurely, allowing hot water to discharge into the drain before the cylinder reaches its normal operating temperature.
A simple check is to look at the tundish (the clear plastic fitting on the discharge pipe) after the immersion heater has been running for around an hour. If you can see a steady drip or continuous flow of water through the tundish, the T&P valve may be passing water and should be inspected and replaced by a G3-qualified engineer.
If there is no discharge from the tundish and the thermostat is correctly set, the next most likely causes are a faulty thermostat, a failing immersion heater, or, in systems with two immersion heaters, the wrong immersion heater being switched on.