Recently our shower (shower tub combo) with separate cold and hot taps started only giving luke warm water. The same goes for the hot water in the bathroom sink. This is only in the second floor bathroom.

On the mainfloor (Kitchen and batheroom) the water is hot hot hot... in the basement the laundry room is hot hot hot...

I turn down the anti-scalding device so that is why the other taps are hot hot hot... I will turn back on the anti-scalding device but I thought it something wrong with the valve.

Anyway I am confused to figure out why the shower taps and the shower and the bathroom sink only have lukewarm water but the other taps in the house have hotwater. For some reason either the hotwater is not getting drawn up to the second floor.

Since the mainfloor and the basement have hotwater... I don't think it is the main mixing valve.

The main line going up to the second floor is split to the sink and the bathroom shower and both are only lukewarm water.

We have a 2-year old direct vent gas hotwater tank.

I have some suggestions that it might be the shower valve and the cold water and hot water are mixing but that would not explain why the bathroom sink is lukewarm too.

Any suggestions?