§ 420.19. Chemical treatment.

Gaseous chlorination systems may not be used as a disinfection method of pool water. Residential swimming pools should meet the following standards:

(a)

Free chlorine. The free chlorine content should be maintained between five-tenths (0.5) and one (1.0) parts per million. (High-free residual chlorine may be used.)

(b)

Alkalinity. The pH level of between seven and one-tenth (7.1) and seven and eight-tenths (7.8) should be maintained. (A higher pH is permitted if high-free residual chlorination is used.)

(c)

Bacteriological quality. A sample of swimming pool water shall be considered satisfactory when the total bacteria count at 35 degrees centigrade does not exceed 200 colonies per milliliter and no organism of the E. coli group are present in a ten (10) milliliter portion or 100 milliliter portion as determined by the membrane filter method. If more than one (1) such sample out of seven (7) collected on different dates is unsatisfactory, the bacterial quality of the pool water will be considered unsatisfactory. Procedures and interpretations relating to bacteriological quality shall be done in accordance with the Standard Methods for the Examination of Water, Sewage and Industrial Waste, 11th Edition (1960).