Update:
I have hooked the unit up to my Dionex 2000 HPLC pump. I can pump 3.00mL/min through the line at ~420 psi. Its hard to figure how the previous user got this line clogged. Its supposed to have DI water. But might it be a good idea to pump dilute acid (Hydrochloric, Nitric, or Sulfuric) through the unit to remove possible scale?
We made 50mL of a solution of 4% V/V Nitric acid with ~8% MeOH.
e.g. Added 10 mL water to a 50mL centrifuge tube, added 2mL concentrated Trace HNO3, filled to 50mL line with premade 10% MeOH reagent.
We used the HPLC to pump this at 3mL/min through the Archon Water Heater assembly at 3mL/min. Lots of fizzing, pressure dropped after 20mL to less than 125psi. Added in a pressure loop and pumped all 40mL through. Then re-primed pump with DI Water and pumped DI water through the Archon Water Heater at 3mL/min for an hour. After that re-plumbed the Dionex 2000 system and put it on to run for a couple hours. It was at baseline within minutes.
Reinstalled the Water Heater Assembly into the Archon 4552. Ran ten 20mL flushes in a row without any problem. Apparently the plugging was due to calcium carbonate. But did not analyze waste for calcium. I'm guessing someone tried to run a carbonate buffer as dilution water and it scaled out in the Archon Water Heater.