In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
I have a radiant heat system using 3/8" Onix tubing - ten 200' loops, single zone, currently fired by a Crown Bimini boiler. For the last seven years , whenever I've purged the system because of circulation problems I get a gritty substance in the water - it's mostly grey , white and tan with some magnetic particles . There's usually a couple teaspoons to a couple tablespoons per three gallons of water. So the questions are: What is this stuff? Where is it coming from? How can I stop it? Why me?