The white stuff on your sanitary fittings is limescale deposits, which basically means the water is hard (high mineral deposits) Limescale will clog valves and ruin chrome.
First you need a sediment filter followed by polypropylene filters which will get rid of all the visible impurities in water. The next step is RO unit which will bring down the TDS (total dissolved solids) to 20ppm (parts per million). But a whole house filtration unit is going to be expensive. If you want to keep sanitary fittings clean without investing in an RO unit, you can try getting a water softner, it is less expensive, but it is only for dealing with hard water deposits, it won't give you clean drinking water.
If you want to keep sanitary fittings clean without investing in an RO or water softener, you need to wipe them with a towel after using them. If you don't wipe them regularly, water deposits will form on them which will harden and destroy the chrome. To clean sanitary fittings with limescale on them, put some harpic on a towel and wipe it on the fittings, it will eat away the limescale.