I know nothing about making EIS using Demin, RO or Deionised water, but a 
person in the UK wants to make some EIS.  Apparently the only water available 
in the UK are those mentioned above, is it OK to use this water for making EIS?
I would be thinking it's OK, it will just take longer to brew a batch perhaps.
I don't think a home distiller is an option here either.

Thanks
N.