The function of lye is to improve the electrical-conduction performance during water electrolysis. Under normal operation condition, the consumption of lye will be nearly zero. Generally, the supplementary of lye will be needed once per year if necessary and the quantity will be a very small. For preparation of lye, solid caustic potash is put into the lye tank which is filled with two-third of DM water inside and then the lye pump will be started to agitate and dissolve caustic potash into the DM water.

The alkaline solution (electrolyte) combined together from the hydrogen (oxygen) separators return to the electrolytic cells via the collection pipe and the filter in which the foreign substances will be removed from the solution, then it will be returned to the electrolyzer via lye pump.