I dont know the whole story....
did they move the heater to a new location o r is this a new install??
You probably have a broken of dip tube in the heater...
Maybe when they installed the heater they soldered the
copper adapter directly on the cold nipple going into the heater...
you are not supposed to heat that nipple up which will
melt off the plastic dip tube where it connects to the nipple
you might want to look closely at the cold nipple inlet and see how badly
it is cooked up around that inlet
and you will probably have to go get a new one