A method for detecting a rinse aid agent in a rinse liquid of a washing machine for household use, in particular a dishwasher, said washing machine comprising: - a control system, in particular of the electric or electronic type, for handling and controlling the operation of the washing machine, said control system being adapted to implement at least one rinse program; - a tub in which dishes are treated by means of a rinse liquid, in particular water, added with a rinse aid agent during said at least one rinse program; - sensing means (5a, 5b, 5c) associated with said tub and connected to said control system for detecting the degree of turbidity of the rinse liquid in the tub, said method being executed by said control system and comprising the steps of: a) taking a first measurement of the degree of turbidity of the rinse liquid in the tub; b) executing a step of releasing the rinse aid agent into the tub; c) taking a second measurement of the degree of turbidity of the rinse liquid in the tub; d) comparing said first measurement with said second measurement; e) verifying the existence of a predefined increase of the degree of turbidity of the rinse liquid in the tub for the purpose of detecting the presence of the rinse aid agent in said tub wherein said step e) comprises at least one of the following steps of: - verifying that said predefined increase of the degree of turbidity of the rinse liquid between said first measurement and said second measurement is greater than a predetermined upper threshold value (X%) for having the certainty of the presence of rinse aid agent in the tub; - verifying that said predefined increase of the degree of turbidity of the rinse liquid between said first measurement and said second measurement -ME242- Set of claims of the AUXILIARY REQUEST - Clean version is smaller than a predetermined lower threshold value (Y%) for having the certainty that there is little or no rinse aid agent in the tub; - verifying that said predefined increase of the degree of turbidity of the rinse liquid between said first measurement and said second measurement is within a predetermined intermediate range for having the certainty that there is rinse aid agent in the tub, in particular the variation of a parameter of the rinse liquid being comprised between said lower threshold value (Y%) and said upper threshold value (X%), wherein said upper threshold value (X%) is greater than said lower threshold value, characterized in that the detection of presence, absence or insufficiency of said rinse aid agent in the tub takes place if the conditions of said step e) occur for a finite and consecutive number of times. - a control system, in particular of the electric or electronic type, for handling and controlling the operation of the washing machine, said control system being adapted to implement at least one rinse program; - a tub in which dishes are treated by means of a rinse liquid, in particular water, added with a rinse aid agent during said at least one rinse program; - sensing means (5a, 5b, 5c) associated with said tub and connected to said control system for detecting the degree of turbidity of the rinse liquid in the tub, a) taking a first measurement of the degree of turbidity of the rinse liquid in the tub; b) executing a step of releasing the rinse aid agent into the tub; c) taking a second measurement of the degree of turbidity of the rinse liquid in the tub; d) comparing said first measurement with said second measurement; e) verifying the existence of a predefined increase of the degree of turbidity of the rinse liquid in the tub for the purpose of detecting the presence of the rinse aid agent in said tub - verifying that said predefined increase of the degree of turbidity of the rinse liquid between said first measurement and said second measurement is greater than a predetermined upper threshold value (X%) for having the certainty of the presence of rinse aid agent in the tub; - verifying that said predefined increase of the degree of turbidity of the rinse liquid between said first measurement and said second measurement -ME242- Set of claims of the AUXILIARY REQUEST - Clean version is smaller than a predetermined lower threshold value (Y%) for having the certainty that there is little or no rinse aid agent in the tub; - verifying that said predefined increase of the degree of turbidity of the rinse liquid between said first measurement and said second measurement is within a predetermined intermediate range for having the certainty that there is rinse aid agent in the tub, in particular the variation of a parameter of the rinse liquid being comprised between said lower threshold value (Y%) and said upper threshold value (X%),