The deionised water in bottles is the same as we use, but at 50 - 60p a ltr bottle it would work out very expensive.
When I do inside work I use pure water and my trad gear and the windows come up a treat, so no reason why it shouldn't work on the pole.
Is there no one who lives near you with wfp gear, you could get your water from them so much cheaper and for a larger amount.