Can you please elaborate on this waste line on top of the pump head? Is it the tubing for seal wash? If so, then it's normal for solvent to be running through there. Also, when changing the frit on the purge valve was the gold seal also changed?
Sometimes a pump can still register a little pressure when the purge valve is open. Are there other symptoms you are experiencing with your pump?
Yes, I believe it is the tubing for the seal wash. I don't use seal wash function or have a seal wash line so I am not sure why solvent is running through there. Usually that line is dry.
When changing the frit, I did not change the gold seal (which I will do now). With the purge valve open, flow @ 1mL /min I see ~7 bar pressure, but when I change the flow to 5 mL/min I see ~90 bar pressure.
I loosened the capillary lines from the mixing chamber (before the damper) and see a pressure of ~ 1-2 bar.