Not too long ago I dropped out the water tank in my 77, 31' Sovereign
. I'm not sure if they are the same tank, as AS changed things so frequently. However, on my trailer there are only two places to access the tank with out taking it completely out. One is the little square in the floor where the fill line, heater hose, air vent, and water line go in. The other is as described in a previous post about the square panel on the bottom of the tank. If you pull that plate off (be prepared for a fight and a lot of PB Blaster), you can access where the water line attaches. Be forewarned that removing the existing water line could take either 5 minutes... or 5 hours. Ask me how I know?
I have all the tanks out of my trailer, and working on them on a bench in my shop is tough enough. Working on them laying on your back under the trailer is nearly impossible... but it can be done.
I have a few pictures of the tank lines and one of the tank on my web page. Hopefully it will give you some insight to what you are dealing with. The water line snakes under the tank and is duct taped in many places from the factory. It's not looking like it can be slipped through.
If it were me... I would pick up a new water pump and try that before attempting any further removal or changing of the lines on the tank. The original pump just may not be pulling enough.
BTW.... I'm just across the bridge from you in Tampa. Welcome to our nightmare! I mean our passion. Yeah, that is what I meant! Passion!