Heater Tap Vacuum Hose connection

[Gazunter]

My AU Fairmont Wagon V8 decided to break a nozzle on the heater tap in the middle of no-where. I have replaced it but can anyone tell me where the other end of the Vacuum hose goes because it either came off when I pulled the old tap out or was never actually plugged in at that other end in the first place. I didn't feel it come out from anywhere so I am suspicious it was hanging loose anyway. Does it go through the firewall?

[Citroënbender]

Yes, it goes through the firewall grommet partly obscured near the washer reservoir.

[Gazunter]

Thanks so much and I'm pretty sure I know the gromet you mean