Water from boiler too hot? Here is how to fix it

For advice on how to reduce the flow temperature of your boiler, please watch our video.

Why is my hot water getting too hot?

If your hot water is scalding or tepid, you might need to consider your combi boiler temperature settings. Here’s how to accurately gauge the temperature of your hot water, and then how to adjust it:

Test your boiler’s current temperature

The first thing to do is work out what causes the water to go too hot. Testing a running tap with your finger isn’t particularly accurate, so you’ll need a thermometer. You can pick one up from most supermarkets. Turn your hot tap on at normal speed. Let it run for around half a minute, then fill a cup. Pop the thermometer into the cup. You should now get an accurate reading. Note it down.

Adjust your combi boiler temperature settings

Next, you should check your boiler’s settings. If you don’t have a combi boiler, skip to the next section.

Most BAXI boiler temperature settings are shown on a digital display. If you don’t have a BAXI, your boiler should have some sort of manual or digital temperature control.

Temperature controls on combi boilers are separated by tap and radiator. This might be displayed by an image of each; ideally it should be clear which is which. Locate the tap temperature, and if your hot water’s too hot, turn it down a little. This shouldn’t affect your radiator heat.

Adjust your system or heat-only boiler

If you don’t have a combi boiler, how to set your hot water temp is different. On a heat only boiler, to change the temperature of your hot water you will need to go to your cylinder and adjust the cylinder stat, the correct setting should achieve a minimum of 60°C. Consult your manual for how to change the temperature. Once you’ve found it, you should be able to adjust it.

Doing this tells the boiler to flow hot water into the cylinder until it reaches the temperature you’ve set. If you’re wondering ‘why is my hot water getting too hot?’, it could be because the temperature was set too high to begin with: cylinders may take a while to cool down, especially if they are well-insulated.

As such, you should wait a few hours, and run the hot taps a few times, to allow the temperature to settle at the point you’ve set it. Then you can test the temperature again with a cup of water and a thermometer.

What causes the water to go too hot?

If you’ve adjusted your BAXI boiler temperature settings and your water’s still too hot hours later, there’s a chance your boiler may be faulty. After all, it is the heart of your home and works hard every day to keep your water hot and your home cosy.

If turning down the temperature doesn’t lower the water heat, it could be due to a faulty thermostat. Your boiler may have a mechanical or electrical issue causing the water to overheat. For instance, the water might run too slowly through the heater, causing it to heat up more than it should. Whatever the issue, you’ll need to call in a heating engineer to service, maintain, or fix your boiler.

Finding the right temperature

Having the temperature set too high is what causes the water to go too hot, but on the other hand turning it down too low might allow bacteria to flourish in your water system. Legionnaire’s disease, for instance, thrives in lukewarm water (between 25-45°C) but is killed at 60°C. Health professionals recommend you keep your minimum temperature at this level.

Having combi boiler temperature settings between 60-65°C is generally comfortable for most people. Turning your temperature down to within this range will possibly make your boiler more environmentally-friendly and your bills a little lower. However, it could make your hot water too cool for your liking. You should strike a balance, and opt for a temperature that everyone in your home enjoys.