Due to the massive volume of scaling obstructing the old volute in/out and HP age, I contracted with a out of state HVAC that owned a flush cart to install a GeoFlo NP Plus non pressurized flow center. The services to be provided were install - flush/refill loop with distilled water and antifreeze and inhibitors to get the loop to the max 20% needed. I chose the GeoFlo NP plus unit because of the external loop header of the system. The NP Plus has a 3 way valve to isolate the HP from the loop for flushing and a LOT of choices to connect flo center. Really handy online geo calculators from company available to aide DYI. Installer arrived - no flush cart. Tested the antifreeze level with a cheap auto tester with floating balls and told me the loop was good to -21 degrees - which would correlate to more than 50% Polyglycol in the loop. He also simply set the circ. pump speed at high rather than check the temp. drop between in/out to determine flow rate. Less than 24 hours later, chunks are visible on the tank bottom. Appearance of very small gravel bits that install manual states will kill the pump before its time. Any suggestions? I can maybe do the flow calculations but what do I need to get a decent dilution number?