My hot water heater appears to work find execpt the down stairs bathroom where the water does not get hot Why? This is the master bedroom and has shower and tub plus sinks.
Do you have a recirculating loop for the hat water so that you have hot water instantly at the kitchen sink?? It could be that there are no or improperly installed or faulty check valves which will cause cold water to mix with the hot water and give you luke warm water in your bathroom.