[mod]

Ive seen a van that I like, however it is currently a DI system and I would need to change this to a RO system as I live in a hard water area

This is what is currently in van:

(350 ltr flat baffled tank, heavy duty Cox hose reel along with 70 metres of 6 mm microbore hosing, 100 psi shureflo pump, varistream, 120 amp battery fully wired up to alternater, 2, 11ltr resin vessel for better purification, 36 ft Brodex pole recently bought, Bucket, fur/squeegy and tds reader. )

What would be needed to convert it to a RO system? Prob sounds like a silly question but this would be my first van.

Look forward to your replys

[Flash..]

You cant convert they are compleatly different things.  If you live in a hard water area like me you will need RO & DI.

[Ian101]

Stating the obvious here but all you would need is some hosepipe, pre filters and a RO filter.

Goes like this

WATER SUPPLY
PRE FILTERS
RO
DI
TANK IN VAN
PUMP / HOSE REEL / BRUSH

or some have it set up like this.

WATER SUPPLY
PRE FILTERS
RO
TANK IN VAN
PUMP
DI
HOSE REEL BRUSH

[Elfyn]

Shouldn't be that much of a job.
DI will be on the outlet of the tank on its way to the brush.
RO is on the "filling" side of your tank.
Just fill your tank through an RO system and leave the rest as it is.