I built a 4 unit building with geo HVAC that was completed in 2007. My Geo installer has since retired and I am having a hard time finding a new guy who will come into Philadelphia. We have not had many problems with the system other than coil replacements in a few of the units. I'm a contractor living in one of the units. My regular HVAC guy can service the individual units. Occasionally I have to add a little bit of fluid to the pressurized loop system with a contraption I made. Occasionally I won't recognize the symptoms in time. It seems like it would be better to have a system that is more easily maintained. Would a Geo Prime tank or an Unpressurized Flow Center be better? Do I need variable speed pumps? How long do the Grundflos pumps last? We have one Waterfurnace Envision, two single speed units, and one two speed unit running off the loop. Do you think a highly skilled HVAC tech could install whatever it is I should install? He does not have a flush cart.