The output of my condenser dryer comes down the same waste pipe as everything else, so it's mixed with dirt and detergent - I wouldn't put it in my steam cleaner.
My water(?) is in a tank that slides out like a massive detergent drawer on a washing machine and it looks okay but you're probably right it might have too many new impurities in it.
If in doubt, simply take a pint or so in a clean pan and boil it off on the hob. Anything left in the pan will also be left in your iron/steam cleaner.
I use tap water and Kalstop
The output of my condenser dryer comes down the same waste pipe as everything else, so it's mixed with dirt and detergent - I wouldn't put it in my steam cleaner.