I installed an open loop geothermal 4.5ton system with a cupronickel heat exchanger in my home last year. I used two "EBV" taco valves which were given with the system but also knew they weren't ideal for the open loop. The other day I went to check on it and noticed that the second stage was sticking and using the little knob I was able to manually open it. After that it seems to open but for the future would the Taco "Geothermal" valves be a better option? I don't know how well those hold up to the hard water buildup compared to the EBV style. My system has been running for a little over 2 years without being cleaned yet and I looked at the drain pipe and there is a thin layer of iron/gunk build up and I was wondering the best way to backwash the system. It will sitll peg the 10GPM flow meter if I open the valves all the way but I don't know if residue in the heat exchanger could be making the system run less efficient than it could be. When I bought the system the person I got it from gave me a gallon of "acti-klean" and the directions state that it's to be used on the outside of the coil. I was planning on filling a 5gal bucket and putting a 55gpm pump in there to circulate the water but I'm not sure how long I should leave it running and if the chemical is the right stuff to use. In summary: Should I backwash the system even if it's flowing enough water? Should I replace the EBV valves with the Geothermal taco valves? Is the chemical (pictured below) the right stuff to use in a diluted solution?