I just purchased this today and it works wonderfully.
I tried vinegar on hard water and scum but it still requires effort to remove.
My shower head arm is flexible metal and hard water deposits build up on and between the “rings”.
I purchased this specifically to clean the hard water deposits.
I sprayed this on and left it for several minutes (maybe 10). When I came back and rinsed it off almost all the deposits were gone. I used a toothbrush to remove a few stragglers. It is good as new.
I used it on the chrome fixtures that had hard water deposits built up and they too shone like new.
I still love my Shaklee Basic H2 for general cleaning but this is a nice addition for a very specific function.
It is too good, but it's true - better than anything polluting I've tried, with none of the guilt. It whitens porcelain stained by hardwater and rust, with minimal effort.