Chromatography Forum

Hi - I have a 2695 that I have PM'd with a new needle and seal pack and also new seals, pistons in the pump. The seal pack adjusted just fine but it's failing compressibility. I can't find any leaks anywhere. Valves 1 and 2 both pass the valve test. I've purged with MeOH for 1 mL/min with a column in place numerous times. There are times the test doesn't even complete because the system doesn't even reach 300 psi! I took off the tubing after valve 3 during the test to see if there was any leakage there and there wasn't. Looking at other posts, it looks like valves can pass the valve test but still fail compressibility. What should I try next? Thanks for your help!

If it was very recently PM'd, call the Waters tech and have him return to fix the leak or replace the check valves (again). If it has been a while, try replacing the check valve cartridges or at lease flushing the existing ones with methanol and sonicating them a little to clean them out (thought this method is far less reliable than just replacing them).

If this does no good, it pretty well has to be a seal pack...

Make sure you dont have a small bubble in the syringe, this can cause compression failure.