Shower too hot or too cold? This is usually the cause
Sound familiar?
You always set the shower to the same position, but sometimes the water is scalding hot and other times freezing cold. Annoying, especially with kids at home. Usually the problem isn't the faucet itself, but a small part behind it: the thermostatic cartridge.
What does a thermostatic cartridge actually do?
The cartridge automatically mixes hot and cold water to the temperature you set. If this mechanism wears out or gets clogged, the mixing ratio is thrown off — resulting in fluctuating temperatures.
3 possible causes
- Limescale build-up — the mixing mechanism moves less smoothly and reacts slower to temperature changes.
- Worn cartridge — after 5-10 years the rubber and springs wear out, making the mix unreliable.
- Pressure difference between hot and cold — for example when someone else in the house opens a tap at the same time.
Check it yourself: which cause is it?
Does the temperature only change when water is used elsewhere in the house? That's the pressure difference. Does the problem persist even when no one else is using water? Then the cartridge itself usually needs replacing.
Replacing the cartridge in 5 steps
- Shut off the main water supply or the angle valves.
- Remove the cover cap and temperature handle from the faucet.
- Loosen the locknut and pull out the old cartridge.
- Insert the new cartridge in exactly the same position as the old one.
- Reassemble everything, turn the water supply back on and test the temperature.
Still not right?
If temperatures are still off after replacement, the cartridge's adjustment ring may be set incorrectly — you can fix this without needing new parts.
Done? Here's your next step
Find the correct thermostatic cartridge for your faucet brand in our webshop. Want to prevent limescale and pitting corrosion in the future? Read our article on preventing pitting corrosion as well.
