started to kit my van out with my first wfp system today,

i have my ro ready to be set up in the garage along with a 1000ltr ibc,
350ltr tank in my van then the pump then the flow controller, the big question is where does the di vessel go?

in the garage?? before the pump?? after the pump??

i,m sure you can tell i,m pretty new to this

thanks in advance