Product review (1 stars): Forget the treatment, go for the cleaner
This is one of those products the company would love to see you continuously buy at the high price tag it comes in.
Save your cash and buy the cleaner instead.  Use it every few months and you'll be fine.  No sense in buying a water treatment when you're using tap water anyway.  The Venta Disc Stacks get dirty over time from build up.  The treatment does nothing to prevent this.  I have two units that run 24/7.  Buy the cleaner, run it for two hours and rinse thoroughly under warm water.  Hope you never have to contact Venta for a disc replacement....their customer  service is awful!