2. Closing & Opening the KCl Refill Hole Refillable pH electrodes have a refill hole Where electrolyte can be added. The level or height of the inner liquid is important for a refillable pH electrode junction. If sufficient electrolyte solution is inside the electrode, the hydrostatic pressure of the liquid column will allow electrolyte to flow out of the electrode at a faster flow rate, and additionally will prevent sample solution from going inside the electrode. Typically, the faster the electrolyte flow rate, the faster the pH stabilization time. However this is dependent on the junction type used. Infiltration of the sample solution can contaminate the reference element and cause unstable or unreliable measurements. Open the refill hole plug during use and close it when not in use.