I believe there may be a o ring that seals that metal tube on the water pump end. I believe your referring to a metal tub that runs from the pump to the other side of the engine? I am not 100% sure but a service manual could shead some light or even parts diagram.

This diagram shows the tube running to the thermostat housing. Do this look familiar? There is a heater hose not to far from the water pump?

http://www.hondaautomotiveparts.com/...y5=HEATER+UNIT