Yet another fresh water tank overflow post.
On our coach (2000/U320/36) the overflow hose exits the fresh tank, travels over the grey and black tanks, and terminates at the top of the bay divider. All of this is on the passenger side, in the manabloc bay. The fitting then deposits the overflow on the bulkhead L bracket. We don't often use full fresh tanks, but we decided this was easy to move and just a good thing to get done. I've read many of the updates done before, so here is ours.
I decided to replace the 1-3/8" ID pool hose; the other option was to splice the existing one to add the length needed, but I did not want a potential leak point. This is the hose we used. 1-3/8" Fill Hose with Flats looks just like what was originally there.
Foretravel attached the hose to the fresh tank with silicone caulk plus a hose clamp. When you remove the hose, you will see the fitting on the fresh tank has a pool hose thread, the type where you twist on a spiral hose. Then, if you want it to be watertight, you add silicone and a clamp. After removing the hose, I had to remove all that silicone so I could get a good seal with the new hose.
The fitting on the wall is a straight pipe with a hose clamp; in our case, there were a few gaps in the sealing of that pipe to the wall. A 1" PVC cap kind-of fits over the existing pipe, but I took the cap to the lathe and opened it up about 1/32" so it was a better fit, and secured it with some silicone and sealed the wall gaps.
To exit through the floor, I choose this Attwood Scupper Thru Transom 1-1/2". Although this is for a 1-1/2" hose, I thought a bit of heat applied to new hose would allow it to expand and fit. Unfortunately, the material that the fill hose is made from does not "work" like that. Instead, I put the scupper on the lathe and turned the barbed fitting down so it would work with a 1-3/8" hose. There is ample material thickness to work with; you are only taking the walls down a 1/16" of an inch.
Next item on the scupper. The rubber flap seals very well under vacuum; try and draw air through it, and it seals tight. The only fresh air makeup I could see on the water tank was the overflow hose; as such, I cut a few notches in the scupper flap seal so makeup air could easily pass into the tank when you get water out of it (and not create a vacuum). I then also placed a plug of brass wool inside to discourage any insects/etc. In its normal condition the flap is partly open, so no pressure is need to allow water to drain.
The last thing is to pick a spot to drill a 2" hole through the bottom of your bay floor. I used a magnet to find (and miss) any of the floor beams and chose an area that still allowed the manabloc vanity panel to be installed. The area I went through was a sandwich of 3/4" ply + 3/4" of foam. I sealed the inside of the hole with silicone and used butyl caulk to water seal the scupper in place. I also added a bead of silicone as a lap sealant on the bottom side.
With everything back in place you can just see the top nut under the vanity panel, the hose fits with room to spare behind the panel.
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Topic: Overflow Hose Relocation (yet another!)