Shower heads lose their effectiveness when they become clogged with mineral deposits, especially in areas with particularly hard water or well water. Metal shower heads are more prone to corrosion from hard water. You can extend the life of a metal shower head by cleaning it regularly. The best way to do this is to put one to to cups of a 50-50 white vinegar/water solution in a plastic bag. Position the bag so that the shower head is submerged in the vinegar water. Secure the bag with tape to the shower head nozzle. Leave it there overnight to dissolve the mineral deposits in the shower head.