Flow Cell Design
AquaChemD's notes compare four ways to mount pH, ORP and temperature sensors, then document a DIY low-flow bypass design.
The four options
1. Inline 2" PVC
Simple and always in the main flow, but high velocity and turbulence can affect readings and expose probes to debris.
2. Commercial bypass cell
Examples include IPS FC100G, Hayward CAX-20272 and Jandy Drudose cells. Controlled flow and convenient sensor mounting, with some port and orientation limitations.
3. Inline flow cell
A dedicated chamber in the main return. It reduces turbulence versus bare pipe but still carries full flow and is more invasive to service.
4. DIY 3/4" PVC bypass
Clear schedule-40 PVC T fittings, 3/8-inch bypass tubing and pressure differential between post-filter and pre-pump points.
Documented DIY orientation
The design uses a vertical cell with bottom inlet and top outlet. The project notes say this arrangement naturally purges air, keeps the cell flooded between pump cycles and allows the top flow switch to verify that the cell is flooded and water is actively moving.
Final arrangement
The documented sensor order places temperature at the bottom, pH above it, ORP downstream of pH, and the flow switch at the top. The notes cite the Atlas Scientific guidance for the pH/ORP ordering.
Materials noted in the project
- Clear schedule-40 3/4-inch PVC
- 3/4-inch NPT sensor threads
- 3/8-inch quick-connect bypass tubing
- Union couplings for maintenance
- Ball valves for isolation and flow control
- Atlas Scientific EZO-pH, EZO-ORP and EZO-RTD with isolated carrier boards