Abstract: The distribution valve has a housing of hemispherical shape with a plurality of inlets for receiving inflows of fluid as well as a blind position equally spaced with the inlets. The housing also has a main outlet for conducting an outflow mixture of fluids and an oppositely disposed second outlet opening. A rotatable distributing element within the housing has a fluid mixing chamber in communication with the openings as well as a duct having an inlet for selective communication with a respective one of the inlet openings in the housing and an outlet in communication with the second outlet opening in the housing. A common angle of preferably 60.degree. is formed between each inlet opening and the second outlet opening to allow test samples to be withdrawn from time to time. The inlet openings each define a common angle of from 90.degree. to 135.degree. with the main outlet opening for a mixture of fluids.