Learn how to adjust your boiler's water temperature with our easy guide. Fix hot or cold water and save energy.
Is your shower turning into a scalding nightmare, or are your taps giving you a lukewarm dribble that’s barely fit for washing up?
Don’t worry - you can sort it out by tweaking your boiler’s water temperature. It’s a quick fix that’ll have your water just the way you like it.
Whether you’re trying to save a few quid on your energy bills or just want a comfy shower, we’ve got you covered with this handy guide.
Quick Takeaways:
Check Water Temp: Measure with a thermometer; aim for 60°C.
Know Your Boiler: Combi adjusts taps directly; system/regular needs cylinder thermostat tweak too.
Separate Controls: Radiator and tap temps aren’t the same - adjust the right one.
Set the Temp: Combi: 55-60°C; system/regular: boiler at 65°C, cylinder at 60°C.
Test It: Run a tap/shower, tweak until comfy.
Avoid Legionnaires’: Keep water at 60°C to kill bacteria.
Check for Faults: No change? Could be thermostat, limescale, or valves - call a Gas Engineer for assistance.
Save Energy: Set radiators to 60-65°C, add a smart thermostat.
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Confirm the Temperature of Your Hot Water
First things first - let’s figure out what you’re dealing with. Run a hot tap for a minute, then grab a thermometer (a kitchen one will do) and check the temperature.
Ideally, your hot water should be around 60°C. If it’s way off - say, scalding at 70°C or chilly at 40°C - it’s time to take action.
Too hot, and you’re wasting energy (and risking burns); too cold, and you might be inviting trouble like Legionella bacteria. Let’s get it sorted.
What Kind of Boiler Do You Have?
Before you start fiddling, you need to know what type of boiler you’ve got, as it’ll affect how you adjust the temperature:
Combi Boiler: These heat water on demand for your taps and showers, so you’ll adjust the hot water temperature directly on the boiler.
System or Regular Boiler: These use a hot water cylinder, so you might need to tweak both the boiler and the cylinder thermostat.
Not sure what you’ve got? A combi doesn’t have a separate tank, while system or regular boilers usually have a cylinder tucked away in an airing cupboard. Check your setup, and let’s move on.
Room Temperature Is Not Water Temperature
Here’s a common mix-up: the temperature for your radiators (room heating) isn’t the same as your hot water temperature.
Most boilers have separate controls for each. The radiator setting (often marked with a radiator icon) usually needs to be around 60-65°C to heat your home efficiently.
But for hot water (look for a tap icon), we’re aiming for that 60°C sweet spot. Don’t confuse the two, or you might end up with a toasty house but freezing showers!
Radiator Temperature Is Not Tap Temperature
To hammer this home, your radiator and tap temperatures are controlled separately on most boilers.
If you’ve got a combi boiler, the hot water dial directly affects your taps and showers.
On a system or regular boiler, the boiler heats the cylinder, and the cylinder thermostat controls the tap temperature.
So, if your taps are scalding but your radiators are fine, focus on the hot water setting, not the heating one. Clear? Good.
How To Adjust the Water Temperature
Right, let’s get to the nitty-gritty. Here’s how to adjust your boiler’s water temperature, step by step.
Grab your boiler manual if you’ve got it - models can vary - but this’ll cover most setups. If you’re unsure at any point, a Gas Safe engineer can help.
Locate the Controls
On your boiler, look for the control panel. You’re after the “hot water” setting - usually marked with a tap symbol. It might be a dial, buttons, or a digital display.
For system or regular boilers, you’ll also need to find the cylinder thermostat, often on the side of the tank.
Check the Current Settings
If it’s a digital display, it’ll show the temperature in °C. Dials might have numbers (like 1-5) or a “min” to “max” range - your manual will decode this if it’s unclear. Note where it’s at so you know what you’re adjusting.
Make the Adjustment
Combi Boilers: Turn the hot water dial or press the buttons to set it to 55-60°C.
If you’re after energy savings, you can try 40-50°C, but test it to make sure it’s still comfy for showers.
System/Regular Boilers: Set the boiler to around 65°C to heat the cylinder, then adjust the cylinder thermostat to 60°C. This keeps things efficient and safe.
Test It Out
Run a tap or hop in the shower to see how it feels. Too hot? Dial it down a notch. Too cold? Nudge it up. Give it a few minutes to settle before you judge the change.
Lock It In
Once you’ve found the Goldilocks zone, leave it be. If the temperature still isn’t playing ball, there might be a bigger issue - more on that in a bit.
How To Prevent Legionnaires’ Disease
Here’s a serious bit: keeping your water temperature right isn’t just about comfort - it’s about safety. Legionnaires’ disease is caused by Legionella bacteria, which can grow in water that’s too cold (below 50°C).
That’s why we recommend keeping your hot water at 60°C - it’s hot enough to kill off those nasties but not so hot you’re scalding yourself.
If you’ve got a cylinder, make sure it’s insulated properly too, so the water stays at that safe temperature. Safety first, always.
Could a Fault Be Causing My Water To Be Too Hot?
If you’ve adjusted the settings and your water’s still coming out like lava - or not changing at all - there might be a fault. Here are a few culprits to consider:
Thermostat Issues: A dodgy thermostat on the boiler or cylinder might not be reading the temperature right.
Limescale Build-Up: Hard water areas can get limescale clogging the system, messing with temperature control.
Faulty Valves: A stuck or broken valve could be letting water get too hot.
If you suspect a fault, don’t mess about - call a Gas Safe engineer to take a look. Better safe than sorry.
The image above shows a standard boiler diverter valve / Heatable
Bonus: Save a Few Quid While You’re At It
While you’re tweaking your boiler, why not check your radiator temperature too?
Setting it to 60-65°C is usually plenty for heating your home - any higher, and you’re just burning cash.
Pair that with a smart thermostat, and you’ll be laughing all the way to a lower energy bill.
All Sorted!
There you have it - your boiler’s water temperature fixed in a few easy steps. No more scalding showers or chilly washes, just water that’s spot on for your needs. And if your boiler’s too old to behave itself, maybe it’s time for a shiny new one.
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