My Gravity Fill/City Water Intake allows water to flow out of the City Water Intake check valve when I turn on the water pump to use the installed water tank.
A Google search identified the check valve installed in the water connection as the problem.
This is the part in question.
On the left is the Fresh water Tank Gravity Fill connection and on the right is the City Water connection.
The brass check valve is built into the brass city water connection
The little round eye at the bottom in the middle is the vent for the Fresh Water Fill.
As you can see all original steel screws are somewhat rusted and it is my habit to change steel square drive screws to stainless steel Phillips head screws.
This is the backside of the new Gravity Fill/City Water box I received. You can see the brass fitting that contains the brass check valve.
I ordered one identical to what I removed and it turned out later to be a VERY lucky move on my part.
The large hole on the right is a twist lock device for the tube that enters the water fill hose.
This is the front or out side of the new box.
The new box has a keyed lock instead of a twist close device.
I decided to go with that to prevent any unauthorized access to my Fresh Water.
There seemed to be TWO types of Gravity Fill/City Water Intake boxes out there.
And here is one difference, the tapered tube that goes into the water fill hose is not an integral part of the Gravity Fill/City Water Intake box (aka box).
This tube passes through the box from the outside and the tapered end fits into the water intake hose which is then clamped in place by a stainless steel hose clamp.
The tube then rotates in the mounting hole until it twist locks in place.
Note the locking tabs on the large (right) side of the taper tube.
When the box is removed all of the years worth of sealant will need to be cleaned off and screw holes inspected.
Not all screw holes may be reusable, plus some may be so close to the edge to be unusable.
The really bad news was, THERE WAS NO EXCESS HOSE OR PIPE AVAILABLE!
The instant the box was clear of the hull, that was the space you had to work in.
Everything at this point was difficult, disconnecting the city water connection, the vent and the fill hose.
On the other hand, the disconnection was so much easier than the re-connection.
Inside the hull was an area bout the size a large pair of boots would fit into.
But there was NO PLAY in anything.
Two inches extra length would have allowed my hands to fit.
The vent and water lines were basically a very stiff type of (I think) PEX pipe which is very stiff.
However, I had no problem reattaching the vent and city water lines.
The taper tube and the water inlet hose for the water tank were the problem. I could not put pressure holding the taper tube into the water hose while screwing the hose clamp tight.
II had it once but when I attempted to twist lock the
taper tube into the box mount the fill hose came loose from the taper tube.
I solved the problem by first connecting the taper tube into the fill hose with the box rotated clockwise so that it pointed to about the 4 o'clock position. Then I managed to get the hose up the taper tube and very care fully tighten the hose clamp.
Then I slowly twisted the box counterclockwise to twist lock the taper tube.
After that I carefully connected the vent and then the city water hose connection (left to right).
It was a pain in the &^*
Next, I filled the fresh water tank so I could run the water pump to check proper operation of the City Water connection check valve as well as checking each connection and or joint for leakage.
Then I re-installed the box into the RV hull. On the left side there were two screw holes that time had got the better of. I put screw back in after placing some toothpicks in the holes. However, you can see that I also added three new screws on the left side.
Before installing the box, I placed a strip of Butyl caulking tape around the outside edge of the box to keep water out of the RV.
I also placed the Fresh Water warning label inside the box.