HI 2500ORP In-line pH and ORP system for pools, spas and waterparks HANNA’s HI 2500 ORP is a reliable, easy to install in-line pH and ORP system for pools, spas and waterparks. Designed to provide a continuous monitoring of the pH of pools and sanitation activity via ORP. The HI 2500 can be ordered completely assembled or with just the controllers ... Read More »