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HPLC Pressure Fluctuating - WKB10722

Article number: 10722


  • Pressure fluctuating from 0-600 psi with and without column.
  • Priming does not help.
  • Peaks are eluting late.
  • Pressure dropout on plunger stroke
  • Loss of pressure
  • Sonicating check valves does not solve the issue
  • Random pressure drop during analysis, results are not affected.


  • Alliance HPLC System
  • 2695 Separations Module
  • 2695D Dissolution Separations Module
  • 2795 Separations Module
  • 515 HPLC Pump
  • 1515 Isocratic HPLC Pump
  • 1525 Binary HPLC Pump
  • 1525 Micro Binary HPLC Pump
  • 600 MultiSolvent Delivery Pump


Faulty check valves.


  1. Replace the check valves with new valves of the correct type (See video below).  Standard check valves, 700000254
    1. PerformancePLUS CV Cartridges, R/S, 1/8-in (700000254)
    2. Check Valve Cartridges, R/S, 1/16-in (WAT270941)
    3. PerformancePLUS CV Cartridge, Ceramic, 1/8-in ( 700002399)
    4. Check Valve, Ceramic (700002333)
    5. Check Valve Cartridge, R/S , Titanium (700002255)
    6. For 2790/2795, also replace Check Valve Cartridge, Ceramic, 1/16-in (700002761)
  2. Confirm that no more pressure drops are present.


If high delta psi or pressure fluctuation persists post new check valves replacement, then check system CD ratio (See video below.)  If CD ratio > 1.80, consider to rebuild pump with Alliance solvent manager PM kit, 700004073.

Replacing Alliance system Check Valve Cartridges

Checking the C/D Ratio on an Alliance 2695 HPLC

2690, 2690D, 2690DUPGD, 2690UP, 2695, 2695D, 2695DE, 2695DEB, 2695DUP, 2695E, 2695EB, 2695INERT, 2695UP, 515, 600C, 600F, 600S, 616F, A-10SSM, ALLCOLCLR, ALLCOLHTR, ALLCOLHTRB, checkvalve, pressure ripple

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