Hi G On newer geysers whole end dome cover of geyser is plastic, not galv plate like yours - is what I was referring to. You can drill small hole (size of probe) at position as indicated and then push screwdriver in making tunnel through the insulation till you reach the tank wall and then slide along bottom edge of the tank. Then push in your probe… The metal outer cover you see is not the tank, just the thin’ish plate covering the insulation.
