I HAVE AN ECONOMY 7 HOT WATER TANK THAT IS SUPPLYING ONLY LUKEWARM WATER AFTER BEING ON ALL NIGHT. I HAVE SWAPPED THERMOSTATS BUT STILL DOES NOT HELP, WHEN BOOSTER IS SWITCHED ON THE WATER BECOMES HOT.
You may have a defective dip tube and could qualify for a free replacement. A dip tube is a plastic tube in your water heater that brings the cold water into the bottom of the heater. The dip tube is designed to prevent incoming cold water from mixing with existing hot water.
Some of the dip tubes manufactured by Perfection Corporation and supplied to most major water heater manufacturers between August, 1993 and October, 1996 were made of plastic and are now disintegrating.