Is your camper a 2004? Trying to figure out by your words how the fresh water tank "drain" hose is going through the camper body. As "many", but not all, fresh water tanks are under the camper and the fresh drain does not go through the wall.
But... you may have one of the few floor plans that have the fresh tank inside the camper and as such the clear drain hose needs to go out through the wall to get out side. Is this the way your camper is made?
Once I'm sure what you have I may be able to help on the hose clamp. Sunline would of used a PEX stainless crimp on connector. By any chance can you post a pic so we can see what it is you have? Or if another member has your floor plan.
Assuming this is the plastic drain valve with a flange sealed to the side of the camper, that flange is sealed with either what they call Putty tape OR better, butyl sealing tape. This is made for campers to seal flanges of any kind to the side of the camper.
Personally I gave up on putty tape,(drys out, create cracks and then water and wick in after a number of years) and now only use buytl sealing tape which has to be used on the rubber roofs, but use it on all camper wall flanges. Doors, cargo holes, corners etc.
Here is one place that sells it. Make sure you ask for white unless you want black. White is actually sort of a cream color. RV dealers sell this too, again ask for butyl or they will give you putty tape.
Butyl Rubber Tape - Flexible tacky adhesive Sealing Tape - PPL Motor Homes
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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