I have a fairly new 50 gallon water heater, temp is correctly set in it, a low flow 1.75 gpm showerhead, yet I have to keep adjusting up the hot water every minute or so, then it starts running cool, then out of hot water... all during a 10 minute or less shower. The math says that I should get at least a 25 minute shower before my 50 gallons of hot water is exhausted, given my low flow showerhead... so why am I running out so fast??