I have very hard water, and the minerals like calcium cling to the hair. After a few weeks it tends to get a bit dull and stiff.
About once a month I rinse my hair in vinegar/water after washing. I just put a cup of distilled white vinegar in a sink of cold water and dunk my hair in it. Apart from dissolving the minerals, the low pH of vinegar and the cold water close the hair cuticles so that they lay flat, which also makes the hair shine.
How do you acknowledge Easter.