On my trailer there was probably less than 1/4" between the end of the barb fitting on the tank and the barb fitting on the back of the drain valve. An interesting problem given that my trailer had the same offset as pictured in Robere's last shot. My tubing did not have a spring; there wasn't enough room for it to do any good. When I opened the access plate, pieces of masking tape with some white goop on them fell out. I think someone in the past had put sealant over the tubing (which was cracked) and wrapped it with masking tape to hold it while it cured. When it all let go, my tank leaked all the water out through the access plate.
Years ago I found a replacement for the valve which is an aluminum plate like the backing plate on the valve. It has a hose barb on the rear and a threaded hole on the front. You can screw in a valve or a plug as you prefer. The hose barb is lomg and has two sizes of barbs. I cut off the smaller end which leaves the larger barb matching the barb on the brass tank fitting, and gives me an extra 1/4" to make the s-bend needed to mate the tubing with the two pieces. I found the plate on e-Bay but the last time I looked they weren't there any more.
I did a temporary repair while on the road. I pulled all the pieces out and replaced the hose barb fitting in the tank with a plug. When I get home I'll mount the plate and the new hose. I'll probably open up the hole in the pan to allow a straight run of tubing while I'm at it.
"You cannot reason someone out of a position they have not been reasoned into"
Al, K5TAN and Missy, N4RGO WBCCI 1322
2002 Classic 30 Slideout -S/OS #004
2013 Dodge 2500 Laramie 4x4 Megacab Cummins