The water quality testing work of urban water supply enterprises can be completed by the water supply enterprise laboratory alone or jointly with the Central Laboratory of its affiliated units. According to the situation and needs, water quality testing items and frequency can be appropriately increased on the basis of exhaust muffler manufacturers in table 2.4.1. For some water quality indicators with low detection frequency, expensive instruments and high detection cost, the unit that carries out the test unconditionally can entrust a testing institution with corresponding project testing qualification to carry out the test. The detection method is in accordance with the national standard "drinking water standard" (GB / T5750), industry standard and international standard. If there is no standard method, other non-standard methods may be adopted, but they shall pass the method verification. Urban water supply enterprises should set up a certain number of online water quality monitoring instruments, such as turbidity, residual chlorine, pH value, and other online water quality monitoring instruments should be selected according to the level of economic development. The on-line monitoring instrument and equipment shall reach the specified sensitivity and accuracy, and meet the requirements of corresponding detection method standards or technical specifications. Online water quality monitoring data should be transmitted to the control center for monitoring and processing. The on-line instrument data cannot be transmitted to the water plant in the control center. The operators of the exhaust muffler should regularly check, record and feed back the on-line instrument data. There is a special person to check and maintain the on-line instrument regularly. When the reading of the instrument fluctuates greatly, the number of proofreading should be increased.