I've got a Merlin system in my van with a resin DI because I also live in a flat (12 floors up) and the water is metered anyway. Like you, I was told by a local janitorial supplier I only needed a DI which was a load of .........................
My biggest problem is water supply. There's a mains tap in the carpark but that means going downstairs every evening for anything between 30 minutes and an hour and a half.
As I only got a Transit Connect at the moment, I use 5 X 25 ltr barrels along with a 30ltr trolley system. I use the one made by Gardiners and it does the job brilliantly. I can use it either from the van or as a trolley.
I do uppers WFP and often, but not always, downstairs trad. On my own I've only ever used the whole lot of water in one day. I've got to know the customers that are not on a meter and if they are at work, I have the merlin running while I'm cleaning their windows. It takes me about 3 or 4 minutes to get it up and running and it sits in my van in an old recycle bin in case of any leaks.
The merlin is a compact unit and is easy to move from the van to indoors if temperatures are to go below freezing.
My whole setup - Merlin RO, DI, Ionics pole, Gardiner trolley and all associated connectors etc, cost £925.
