The most common effect of hard water on pipes is decreased water availability it is most noticeable at showerheads and taps.
Over a period of time, the constant build-up of lime scale within the pipe allows less and less water to pass through. Water taps may eventually deliver only a weak stream of water. Showerheads may dribble instead of spray. The lime scale may also build up within the tap itself, interfering with the shutoff mechanism and causing the tap to drip constantly.
The most effective way of treating hard water is to install a proper water softener.
Water softeners are working actually on a very simplistic principle, see image below for illustration: