I decided to finally figure out what is keeping my pop ups from going back down. Borrowed a removal tool and removed 5 pop ups. What I found freaked me out. Chunks of dark gray stuff came out. I ran the system and more of it came blasting out of the holes. They were very fragile and could break easily, I figured its some calcium build up. I put together some acid and water mix and put one of the mysterious chunks in and it foamed like crazy. Now if this is indeed calcium, how would I get rid of it from the pipes of the pop up system ? how would you prevent it ?