My 6 year old Raypak RHP100 Heat pump pool heater is leaking from a small clear-rubber tubing that comes off the water manifold. The tube goes to an open (drain?) fitting on the bottom of the housing. I don't know what would keep this from leaking all the time as it looks like there is nothing to prevent water from coming out this tube/opening. But it just started leaking recently, so something has gone wrong.

If anyone has experience with these heat pumps I could use some advise.
The tubing is not even shown on the parts breakdown (meaning I probably have to buy the whole manifold if I need a part).

here is what it looks like: