Hi, my furnace is leaking from the backflow a couple days after I had a plumber clean the coils with nuratic acid. The system was working OK before hand just wasn't getting hot water for longer then 5 minutes at a time on the second floor. Now there seems to be a constat flow of water and banging in the pipes, along with no psi and leaking from the backflow... please help

Furnace, coils and hot water are not normally in the sane sentence. Where are you located?

You should remove the valve and clean or replace it. Any other valves causing problems should be cleaned or replaced, but most can be cleaned.