stiebel eltron

[Adam]

Hi i am fitting a wall mounted water heater made by stiebel eltron. Once again the instructions are rubbish. the pics in the instllation guideseem to show what apperas to be an air vent, coming up from the hot water storage part and terminating above the cold water. However in the tank there is just a hole from the top storage part to the bottom part i am wondering if i should put a vent in or not. There is no mention of it in the instructions.
I would appreciate any feed back.

Thanks Adam