Wow-what a product love it so much, I come from a rural property and use bore water, this leaves rust and calcium build-up on showers and toilets I spray with Koh each night and clean every night when in the shower with their wonderful sponges. I am now getting the rust off the shower and I can see the white walls again just about to start on the toilet but can't see a problem there. Love it that it is eco-friendly as we also have a septic tank, Thank You so much KOH for this wonderful product. Wish I could tell all the rural people about this product, will now only buy this for all my cleaning purposes as I don't have to wear a mask to clean anymore.