The invention relates to a method (100) for maintaining an equilibrium of a physico-chemical parameter of a medium, and for recovering said equilibrium in case of loss of the latter. More precisely said method makes it possible to estimate the relevance of a corrective action on said medium in order to recover an equilibrium. The method (100) is implemented by the processing unit (UT) of a system for regulating said medium. The invention applies in a nonlimiting manner to the regulation of the equilibrium of the bathing water of a swimming pool.