There is no tank heater.
The water is pumped through the perfect heat coils, into the heat
exchanger, and out of the front of the machine. Any excess flow due
to pressure regulator, and not spraying, is re-directed into the tank.
so if you wish to heat the tank, use the grey drainage pipe to pump the water out,
and place the open end in the tank.
As you work the tank heats up due to the excess re-circulating anyway.
My technique is switch the heater on immediatly after pouring the first bucket.
If it's really minging i switch the vac motors on after the second bucket, to preheat
the coils.