The port needs to be below the top of the fresh H2O tank. That's necessary because of the shapes of Annie's inner and outer walls and framing. So, we won't be able to use a gravity feed. Instead we'll depend on a check-valved city water port as our only inlet.
I will selectively use that inlet to fill the tank with pressured city water, winterize the sink faucet lines, use our on-board water pump to fill the tank from (filtered) streams or lake water, or (rarely) use city water to drive the faucets.
Anderson Brass makes a port assembly that has a four way valve and a city water inlet...exactly what we need.
Fortunately, the 4-way valve is available as a stand-alone part.
I already had a standard gravity+city feed assembly, so I cut out the gravity feed, and installed the valve in it s place.I mounted the valve on an aluminum plate that I screwed onto the assembly
Then off to Annie to perform surgery. First mark where the wound should go. I drilled the 2 upper corner holes from the inside. Then marked the cut lines on the outside. The water assembly fits neatly in one of the inner wall's openings, but care is required to make sure the assembly is properly centered.
If Annie was a side of beef, at this point I would exclaim "Holey Cow, what a fine cut!":
Caulked the box and screwed it in.
The aesthetics comittee had previously painted the box to match Annie, and did a fine job!
Not only that, but the door works!