the system is quite basic but purchasing everthing and making sure everything is compatible and then preparing your van putting the system together and fitting to your van took a lot longer than antisipated, but then im a very maticulouse person, so everthing has to be right!Best place to start is the size and type of tank,how to fit tank securely and safely in van.then are you gonna produce water in the van or have a holding tank and transfer it,youll need RO unit and DI vessel,then pump and flow controller,hoereel and hoseline and all the fittings to connect everything together,ive routed hose lines to fill the tank and for my water flow through the van floor so these actions can be achieved when van is locked.A leisure battery powers the pump and flow controller,this requires a charger,size and quality of pole depends on type of work and budget,TDS meter measures purity of water.Some type of valve to stop water flow to pole is advised, i like to fit a trigger for best control.It took me lots of time researching all the parts to get best quality at the best price, and being an ex engineer i found the build quite enjoyable,although i had two vans to kit out and it took longer than first thought, its worth the effort!!!! Dave