Fuel level sending unit

Hi, I just had a gas tank for a KZ1100 shipped from the US to the UK and it is pretty good, including fuel cap & fuel level sending unit. It has a rubber hose attached to the black plastic cover of the sending unit. Can anyone enlighten me please as to the function of this hose and where it should be routed. It looks to me just like a drain hose but surely if the unit is seated correctly it should not leak.
Thanks Tommotbird

I have the same set up on my 82 GPZ1100 B2. It is a safety type of drain so fuel does not get around an ignition source and cause a fire. If the gasket would fail the plastic housing and drain tube will allow the fuel to go to the ground.

Most of the black covers w/hose are cracked and won't stay in place. I generally end up getting sick of trying to make it stay on the sending unit and just toss that piece. wg