What hose is this?

[Steve A]

You need a new drain plug. That tube you mentioned is where the coolant drains out of when you release the drain plug.

Dorman part 61133

IIRC there is an o-ring on the drain plug and replacing it might stop your leak.

 

[haks310]

Yup, small rubber o-ring that gets eaten up anytime you mess with the drain plug. You would just need to find one that would fit.