I've been working on this trailer on what I like to call "Phase 2" since the beginning of this year. That work is documented here: http://www.airforums.com/forums/f46/phase-2-has-started-new-kitchen-cabinets-and-front-underbelly-floor-and-restoration-115482.html
I thought it would be better to post this upgrade separately so that if folks have questions on the fresh water fill then what I've done may help.
I've got to thank "Wabbiteer" for giving me the heads up on this issue. In a nutshell, the standard fresh water fill on these 70's (and maybe earlier and later) trailers really isn't very sanitary because there is nothing to stop rain runoff from traveling down past the outer door and getting into the tank. I recently dropped the tank as part of the front frame maintenance and I was really surprised at how much black garbage was in the tank. I filled the tank with a couple of gallons of bleach and got it fairly clean again. Without dropping the tank, I doubt it would have ever been close to being sanitary and even now, I will probably cook with bottled water and save the tank for washing and flushing the toilet.
I love to hunt for bargains and have been doing well shopping off Amazon and their warehouse deals. About a week or so ago I managed to find a "used" Atwood marine boat fill for 16 bucks shipped on prime. Check. While I was getting some aluminum for the new kitchen backspash I also got a small 7x7" piece of a heavier grade aluminum as a mounting plate. Check. What was left was to find a hose that would fit both the new fill and the tank elbow fitting. I had previously bought a section of hose but could not get that to fit on the old fitting and that hose would not fit the new one either. On a whim I stopped off at a pool supplies store and picked up a section of skimmer hose that fits both ends just fine (different diameters to boot) Check.
So this is what was under the sink previously:
I'm not sure what the PO was thinking, but he had it all patched up. The original hose looked like something that would come with a swimming pool filter. Yesterday I drilled out the old rivets but had no luck getting the door assembly out. I wanted it intact in case somebody else wants to try and use it. I started again today and managed to get it loose and moving:
This is from the inside, the factory cut the lovely hole:
This is how it came out, I was very gentle, but the 40 yo plastic had seen better days. I suppose it would still be serviceable with some help.
Here is the new water fill fitting and the plate I made for it:
Gooped up with polyurethane sealant. I could only get a tube of black at the local roofing supply place.
The new plate installed where the old filler sat. I used the black poly sealant all around the perimeter and put a dab on each rivet. This is the first time I used olympic rivets, so now I have to get them shaved down and pretty. I have a rivet shaver, but I have no bit for it. The bit that fits the drill mounted shaver might fit, but they are overcharging for it by a factor of 5, so I may try and find a straight cut bit for 20 something and see if I can dial it in to just brush the top of the rivet.
Here's what she looks like from the inside:
I had a piece of the vinyl cover aluminum kicking around from the previous bath remodel so I cut it down and drilled a hole in the center for the fitting:
And here it is with the new filler hose installed. Gotta love the lovely blue aqua color:
And in case you think I'm kidding about the crap that gets in the tank, here is one of the elbow fittings from the original hose with all the black sediment that sat in it for years:
Stainless fill: 16
Aluminum plate: maybe a couple bucks, he didnt itemize.
Cleaner water: Priceless