I have three floors in my house, all with base board heaters. Each loop is
a zone. They all come off my Burnham oil furnace.

I had to drain the system to replace a section of pipe on one of the zones.
When the water drains out it comes out really dirty. I know my water is a
little hard so is this normal or do I need to add something to the water in
the loops when I fill it back up?