i am moving out of my house right away, i am leaving behind a 3.5ton open loop. the water comes out of a 47' well and is returned to a old wooden cribbed well about 20 feet away, there is alot of iron bacteria in the water, pumps, valve's, and pretty much everything gets muck in with a rust colored clay like slime. what i have been doing in the past 5 years is once a a year draining as much water as i can from my heat pump, filling it with as much muriatic acid as i can get in, leave it for an hour or so, then fire it up and flush it out with fresh water.  i have a clear flow meter that will also be so mucked in you cant read it, once the acid hits it, it is as clean as new.  i do have a cupranickel coil.  is this method of cleaning ok? are there better methods that people are using?