We have a combi boiler situated in the kitchen. Yesterday the water upstairs will only run luke warm. Water from the tap in the kitchen still runs extremely hot. The water from both the bath tap and sink tap (ran for in excess of 5 mins) does not heat up. Water from kitchen tap gets hot quickly ( I appreciate it is next to boiler). Previously took less than 10 seconds to get hot water through taps upstairs. Heating is still fine. What could be causing the water to be fine downstairs but not in the bathroom? Any help appreciated.

We have a combi boiler situated in the kitchen. Yesterday the water upstairs will only run luke warm. Water from the tap in the kitchen still runs extremely hot. The water from both the bath tap and sink tap (ran for in excess of 5 mins) does not heat up. Water from kitchen tap gets hot quickly ( I appreciate it is next to boiler). Previously took less than 10 seconds to get hot water through taps upstairs. Heating is still fine. What could be causing the water to be fine downstairs but not in the bathroom? Any help appreciated.

Update - I have noticed that if the heating is on before you turn on the tap then the water is okay. I would understand that a valve was stuck if only the water downstairs was cold but this runs hot whether heating is on or off. Also I have checked and there is only one hot water outlet running from the boiler (just in case there was a separate one for downstairs and upstairs). Stumped! Have gas man coming out tomorrow as we are on a plan.

Update. It turns out there was nothing wrong. Due to the extremely cold weather the engineer said the water coming in from the mains was colder and the boiler can only raise the temp by x amount. Running taps a little slower seems to resolve problem.