We have hard water so after some time our shower heads get calcium buildup. The solution to get rid of it is super simple and of course involves distilled white vinegar.
In order to get rid of the nasty buildup, all I do is fill a little bag with some pure distilled white vinegar and fasten it around the shower head with a rubber band. As soon as the shower head comes in contact with the vinegar the calcium deposits start dissolving. I let it sit for several hours before I remove the bag with the vinegar and the shower head looks as good as new.
I told you - SUPER simple and no scrubbing or anything involved.