di water loop

DI water loops continuously circulate deionized water through the distribution system to maintain purity and provide instant availability. **Why recirculate**: Stagnant water degrades - picks up contamination from piping, bacteria can grow. Continuous flow maintains purity. **Loop design**: Supply loop from DI plant, return loop back to polishing system. Tools tap off supply, unused water returns. **Velocity**: Maintained at 3-6 feet per second typically. Fast enough to prevent stagnation, prevent biofilm, scrub pipe walls. **Pressure**: Adequate pressure throughout loop for tool requirements. Pump systems maintain pressure. **Return treatment**: Returned water gets UV treatment, filtration, and polishing before recirculating. **Monitoring points**: Resistivity, particles, TOC monitored at multiple loop locations. **Dead legs**: Minimized - any branch to tool should be short with regular flushing. Dead legs contaminate. **Loop materials**: PFA, PVDF, or high-purity polypropylene. All materials must be compatible with UPW. **Balancing**: Flow balanced to ensure all areas receive adequate flow and pressure.