Here's a rough layout, just for the purposes of showing off the back of my van!

No real question here.

And this is a simple question:

When we're pumping water out of the tank, it'll create a vacuum; so how does air get into the tank? I can't see any valve, like what you'll find in the top of a shurflo backpack that lets air in as water is used, so what's the score with this?
Now that was the easy question!

But look at the state of this rollox:

Now, what wire goes where?
