At the same time I fitted a dedicated filtered water tap to draw water from one of the tanks. This meant a seperate 12v pump. It was an expensive exercise which could have been avoided if I had agreed to the suggestion when the van was being built or had wifie agreed to a simple hand pump to draw the drinking water from the tank. Despite the water filtration system & the Shurflo pump having anti-drain back valves, enough water still drains from the pump to reduce pressure & for it to start pumping. Therefore it starts pumping without the tap being open and continues to run. The day after installing it I left it on to make sure there were no leaks. After getting home from work I found the pump running & it was too hot to touch. No idea how long it was running & it was lucky it didn't start a fire & I'm not sure if I damaged the battery in the van because it wasn't plugged in to shore power at the time. The van battery was reading just over 12v however. Next will the the installation of an in-line one way valve on the pick up side of the pump although I would rather a 12v timer switch (push button thing like they have in some amenity blocks for lights) although I can't find anything like that for 12v systems.
Our two tanks are plumbed separately and we have two pumps. I've been over all the hosing and have re-done some (I'm not a plumber so it's possibly not the most expert of jobs) but I can leave the main pump (Shureflo) on all night and it doesn't lose pressure. The other pump was a bit of a problem because it's not self-priming and it used to leak but I've got it fixed and it now remains sealed for ages (10 days at least).
The two-tank idea is probably for the same reason you're doing it. I want one of my tanks to have just water that we consume (drinking, tea, coffee, cooking) - never to be compromised - and the other we can top up from questionable sources as a last resort, as it's only used for washing.
After that I have to install the rear view camera system which was bought at the Melb caravan show. The intention is to do it without drilling into the van. I will contact G & S Chassis after Easter & see if they can manufacture something in a vaguely similar fashion to the spare wheel carrier on the bumper.
Good luck with your projects. The list usually gets longer while the time gets shorter.
I've been thinking about a reversing camera but have no idea how I'm going to run the wires from the back through the van. I am not confident at drilling holes in the roof!
Good luck with yours, too. My list has pretty much come to an end - we're happy enough with the van now. It's maintenance, maintenance, maintenance! After the maybe water tank, I've got shocks and springs to replace.