Alan,
yes it does take a lot of cans, but you only have to fill the tank once. We find three cans to get things going and prime the system and then another 3 or 4 and it's glugging out over your foot.
If away for a couple of days no need for any more filling. If away for longer then each time we empty the bucket of waste water we put another can of fresh water in the tank.
Another tip is when leaving camp to move on to another is to pull the bung in the bottom of the tank. Do not run it dry through the taps. It is perfectly safe to run with the system primed ready for arrival at next site.
I've also added an isolation switch next to my tank so I can leave the 12v on without fear of a knocked tap starting the pump. This also allows me to leave the taps open over winter whilst the vans 12v system is still live with lights usable.

Colin

This might help as a starting point for you:- 2017 Triton 430 - extras and modifications
I don't know which model van you have, but on our 430 you can access the mains socket circuit easily under the kitchen sink. Remove the screwcaps, unscrew the bottom horizontal panel and you will see the main cable. Cut into this and install a 30amp terminal block. From here run an extension cable to under the bed, just inside the rear hatch as in the link photos.
I have since replaced this with a double, one side to feed my internet booster router and the other to supply power to the awning, or plug the lead in that goes through the floor to an external socket fitted under the van. I've also now added a screw top access hole through the floor to feed my router cable or alternative TV axial cable.This was made up of odd plumbing wastepipe bits designed for a soil stack, along with a couple of iroko hardwood discs.
Internal sockets etc to match originals came from https://clearcutconversions.co.uk/produc...s-and-switches/ If you phone them up they will do a mix and match to your needs and are very helpful.
The external socket was a generic unit bought from the likes of Toolstation https://www.toolstation.com/bg-ip66-13a-...d-socket/p36199
Your idea on a splitter for the mains hook up has been used by several members and is an option you could follow.
.
Off at a slight tangent, we do not hook up our van in the "normal" way. We developed a method that we used when the boys camped with us. We run a domestic extension cable drum with the 3 pin end replaced with a suitable plug to attach to the bollard. The cable drum is unwound and put into the awning or under the van. We test the polarity on the drum and use a short correction lead if needed. From the drum we run a 5m lead into the vans hook up, or extension leads [via a plug in circuit breaker] to the boys pup tents or wherever needed.

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Colin