Purified Water Storage and Distribution System

The purified water is prepared by purified water generation system (Reverse Osmosis System) and collected in purified water storage tank of required capacity and distributed by a centrifugal pump for loop recirculation.

At different points of use, the separate heat exchanger is provided (if required) to bring down the temperature of hot circulating water as and when required. There is a back pressure valve in the return line. Instruments and on/off valve are for controlling and monitoring the system operation and water quality. 

These are controlled from a centralized control panel consisting of a PLC board. The distribution piping consists of sanitary tubes, fittings, valves with orbital welding and triclover clamp in the manufacturing area and for instrument connections. The water through this piping is supplied to various user points and circulated back to the purified water storage tank passing through the ultraviolet light having minimum radiation dose of 30,000 μW-sec/ cm².

The material of construction for a storage tank and distribution line should be SS 316L. Vent filter in the storage tank should be of 0.22µ size and water should be filled in the tank through spray ball spraying water on the whole inner surface of the tank.

The dead leg can cause stagnating of water causing microbial growth, thus dead leg should not be more than 1.5 times of the pipe diameter. The slope in the entire loop should not be less than 10 mm/meter. There should not be any leakage and pressure drop during hold time. Passivation of distribution loop should be done with 3.5% v/v nitric acid solution for a period of not less than 120 minutes.

Related: Passivation of Purified Water Storage Tank and Distribution Piping

Validation Test: Performance Qualification of purified water storage and distribution system is carried out in three phases.

Phase I Validation Study: Once purified water storage and distribution piping has been verified, having installed as per installation qualification protocol the initial phase of purified water system validation is started. In this phase, water sampling shall be done from all sampling points for a period of minimum 15 days.

Phase II Validation Study: This study is done to demonstrate that the system consistently produces the desired quality of purified water when operated in conformance with the SOPs. The sampling shall be done from all the sampling points for a period of minimum 15 days.

Phase III Validation Study: The third phase of validation is designed to demonstrate that when the water distribution system is operated in accordance with the SOPs over a long period of time (one year), it should consistently produce water of desired quality attributes. During this period sampling shall be done as per the routine sampling plan which will include, testing of samples from each user points at least once in a week for complete analysis.

Also see: Purified Water System Validation

Therefore distribution system plays an important role in maintaining the quality of purified water. It should be maintained and validated properly.