I'll work on a photo, not real good at that sort of thing. Filling is easy, no gurgling or spitting back. The fault with the original breathers isn't the size, it's the fact that they are effectively blocked by water. I usually fill with an ordinary garden hose shoved about a foot into the fill tube.

This plumbing stuff isn't rocket science and many folk may see my effort as a bit rough.  But it works for me.

The original filler pipes looped down under the chassis and looked untidy.  I cut them and used elbows to get a neat bend under the chassis.  The breather pipes similarly looped under the chassis and were always holding water.  This affected both the filling and pumping from the tanks.  I cut them off.  You can see the remaining bits hanging down.  I left them this long in case I needed them in the future.  Not likely to happen.

You can see the tank selector tap in the top right corner of the photo.  I don't need it now so it stays in this position.  There's a little green tap on each tank feeder line, and I make sure there's only one turned on at a time.

The tap for the front tank is just out of sight but looks the same as the others.  This is an outback van and it's easy to reach underneath to change the taps.

Looking from the back of the van you can see the three new breather pipes, strung through the chassis to avoid any deep dips that might hold water.  At the back they extend upwards so they are higher than the tanks. They are concealed behind our alloy box on the bumper but you could bring them up behind the spare wheel if you had one there. A few little drill holes allow air in rapidly but ensure that not too much water escapes when we're going up hills.

I've just noticed near the mudflap on the right you can just make out the tap for the grey water tank.  This stays closed except when there's drainage available.  The Jayco Sterling chassis is thought to only support three 82l tanks because the gaps between the chassis cross members are too small for any more.  Don't believe it!  There's just enough room in the space in front of the rear tank, but believe me, it's a mongrel of a job.