On Fri, 22 Jun 2018 00:44:01 GMT, Steve
m wrote:

We have very hard water and some of our pvc pipes are developing limescale
buildup. what is the best way to dissolve this?

If it is all PVC, drain the system, cap the pipe at each fixture, fill
it with muriatic acid from the highest point, take a nap and flush it
out tomorrow from the lowest point. It will be clean as a whistle.
Just be aware this will bubble up a might so be careful.