Gray water tank

1982 Pace Arrow, I drained the MH tanks from winter and washed them out a few times last weekend. Last night as I walked by the rear of the MH I noticed a small drip coming out of the Gray holding tank, where the drain is, I noticed that there is a hose clamp where it connects to the drain valve. I also noticed that there is a crack (I think) its a pretty straight line under the clamp. I have had this MH since last year and never had any leakes and I guess I never noticed the crack before but had seen the hose clamp. I tried to tighten the hose clamp but could only turn maybe a 1/8 turn (its hard plastic) it slowed the drip but didn't stop it.
Question is: Is that the way it was connected to the valve?
should I replace the clamp or try adding another one? I haven't been outside yet today (YES ITS SNOWING AGAIN) I left the heat on and the water heater going over night because they said snow so I presumed it would get down too 32 but when I got up @ 5:30 the TV guy said it was only 42 so I know it didn't freeze. any ideas?
Thank you Tim