Water tank plumbing and venting

[Pongo]

So I gutted a factory-built SportsMobile to redo the interior. I'm about to put the water tank back in. I went back to the picture of the original tank and how it was connected. After looking at it for a while, I can't figure out how it is venting. Can anyone explain whether the setup in the attached image is good and how it's venting? The pipe in the lower left runs to the rest of the van, where it tees in a couple places to go to the sink, the water heater, and the fill inlet on the exterior of the van. I've read about a lot of people doing vent hoses / pipes that rise a ways above the tank and then go back down through the floor, which makes sense. I'm guessing it also needs to rise higher than the sink? I'll probably plan to do that if I can't understand the self-contained setup in this picture.

[Pongo]

Sorry, never mind...I just realized the top loop of Pex also goes through the floor - it doesn't connect to the main line as I originally thought (from not examining the picture closely enough).

[gahamby]

On mine, that top left fitting would be the vent/overflow.

[gregchick]

I have a Ford Transit van, chassis mount 15 gal. tank, the vent opening was put in as an open port at top side of tank. Water splashed out, I put an elbow pointing up, couple inches tubing with some 3M scotch Brite scrub pad stuffed into the tube to keep out debris, yet breath.. Are there say half ounce spring loaded air inlets that allow suction then spring closed that are 1/2" port and mountable under a van
?

[gahamby]

I don't know of a two way check valve, but there could be one. I need the top opening on my tank for both vent air coming and overflow water going out. The overflow cannot keep up with the city water filler for long at all.

[gregchick]

Thanks, technically it would not be a check valve, yet your use of the word was clear to me. I use the "City shore" water hose pressure to fill the tank, when it overflows, I stop. So I also use my vent as an overflow.
I think the water splashing around while driving allowed the tank to lose half the water first time I drove it. I found out my tank was empty after one 2 min. shower!
Is this posting going to the whole general posting place so many will read and reply?

[gahamby]

Yes, this thread is visible to all.

[Lilnuts2]

Looks like they made it way more complex then it needed to be.

[posplayr]

Originally Posted by Lilnuts2

Looks like they made it way more complex then it needed to be.

The structural support to restain that water tank is especially simple though albeit woefully inadequate.