Last Updated on March 18, 2023

Our Baxi Duo-Tec combi boiler has been great and hasn’t let us down once. We don’t have a thermostat on our shower (it’s just a tap-fixed thing) so we use the hot water dial on the front of our Baxi Duo Tec. Until a few weeks ago this method of setting the hot water temperature worked a treat – we’d set the water temperature to 45oC on the front of the boiler and then just switch on the hot tap on the bath tap/shower combo, have a lovely shower then set the temperature of the hot water back up to about 60oC. Actually that’s not entirely true; usually I’d forget to set the hot water back to ‘very hot’ and would only realise when I did the washing up.
A few weeks ago we started setting the hot water to 43oC instead of 45oC, then 40oC instead of 43oC. In short, we were having to set the Baxi boiler to a lower water temperature in order to have a tolerably hot shower. Both my wife and I thought this was our imagination, but before much longer we were having to set the hot water temperature dial as low as it would go, and it was still hot enough to cook our flesh.
I tried to google a few phrases like ‘baxi duo tec too high temperature’ but didn’t find any conclusive information on how to fix the problem. Then the error code E50 started flashing up and we lost all hot water.
How to fix the Baxi Duo-Tec boiler hot water problem.

Call your plumber. I know this seems like an obvious answer, and if you’re a bit more technical than I am then you might be able to fix the problem yourself, especially when I actually tell you what causes the problem and how it is fixed.
The hot water sensor (pictured on this post) tends to leak a little, and if you live in a hard water area then this causes limescale to build up on the hot water sensor, which of course affects how hot the boiler thinks the water is.
The thicker the limescale, the higher your boiler will raise the water temperature. You can probably replace this part yourself, apparently, it’s a common problem with all boilers in a hard water area. I called our plumber because he’s a top lad and I didn’t want the responsibility of having to tell my wife I’d broken the boiler and flooded the house trying to fix the hot water problem myself.
Did you find this information helpful? If so please feel free to buy me a pint…
Our Baxi Duo-Tec combi boiler has been great and hasn't let us down once. We don't have a thermostat on our shower (it's just a tap-fixed thing) so we use the hot water dial on the front of our Baxi Duo Tec.