dazmond
With a TDS of 35 you DO NOT need to consider a RO unit, a DI only system will be fine. That's a lot less hassle to begin with. A twin ( 2 x DI vessels ) is the most economic way to go with a DI only system. It couldn't be more simpler for you to set a whole system up from scratch without the need for an RO.
People will argue all day about the pros & cons of WFP. The truth is, it's a very good method, with the right equipment & used in the right circumstances BUT it's not a total solution. It will clean some windows perfect & others far from. It will be twice faster than trad on some work but slower on others, there is just no black or white with WFP I'm affraid.
You will soon work out which work benefits from WFP & which doesn't, use it to your advantage where you can & trad the rest, it's as simple as that, like con' roofs- you'll never trad one again!
Do not be conned into buying an RO though, trust me, you do not need one. If you do go wfp, I'll give you all the info you need on setting a twin DI system up, it's very simple!
