When I used to work in a lab, we had our own de-ioniser that we used to purify water. When it was exhausted, we'd simply make up the chemicals and regenerate it ourselves. It wasn't difficult at all. It needed about 10 Litres of Sodiom Hydroxide Solution, and 10 Litres of Sulphuric acid solution.
It was quite easy to flush and then rinse the tanks, and the total cost of those chemicals was not more than about £10
Afterwards the resin was fine for about 10-11 months.
Surely this is the way to go, rather than buying new resin at £80 a go every time?
It would require buying the two types of resin seperately though (Not "mixed bed"), and it would need to be kept in seperate tanks, but this is not a difficult problem is it?
Peter, you make these contraptions - what do you think?