I'm stumped...we have two 40gallon water tanks run parallel so hot water shouldn't and never has been a problem, until recently. We've been running short on hot water in the tub in our master bath and the hall shower, and now this afternoon along with the tub the sinks in the master bath. The pressure is fine and the water is warm, but not hot at all. I've cranked up the temp on both water heaters, the flame is going strong and they're both really hot to touch. I thought initially maybe something was up with one of the valves to the tub since it probably has an anti-scalding valve, its probably 15 years old so maybe something has gone wrong, but it seems really odd that the hall shower is having the same problem (its only about 4 years old, single handle moen) and now the bathroom sinks as well. All copper, pressure is fine, tanks appear to be very, VERY, hot...but only warm/hot by the time we get it out at the tub and shower.
For the most part its happening at random times, not necessarily after running washing machine and/or dishwasher and sometimes when neither has been run in hours.