For any pool service, the tech visit screen surfaces a chemistry grid. The tech enters six readings; the system computes LSI, flags anything out of range, and suggests dosing.
The six readings
- Free chlorine (FC): 2–4 ppm for chlorinated; 3–5 ppm for saltwater.
- pH: 7.4–7.6.
- Total alkalinity (TA): 80–120 ppm.
- Cyanuric acid (CYA): 30–50 ppm outdoor.
- Calcium hardness (CH): 200–400 ppm.
- Water temperature (°F).
The LSI calculation
The Langelier Saturation Index combines pH, TA, CH, CYA (corrected), TDS, and temperature into a single number. It represents water's tendency to scale (positive) or corrode (negative). Servicio computes LSI automatically from your readings and displays it as a colored indicator:
- LSI between -0.3 and +0.3: green. Balanced water.
- LSI below -0.3: amber. Aggressive / corrosive. Recommend raising alkalinity or calcium.
- LSI above +0.3: amber. Scaling. Recommend lowering calcium or pH.
Where readings are stored
Each reading is written to pool_chemistry_readings tied to the visit. On the property detail page, the "Chemistry trend" card plots the last 12 readings of each parameter. You and the client can see the drift over time — which is what drives the "partial drain" conversation in year 3 of a saltwater pool.
Out-of-range flagging
If any reading is outside the recommended range, the tech screen shows an amber flag with a recommended action:
- "FC is low at 1.2 ppm — recommend shock."
- "pH is high at 8.1 — recommend dose with muriatic acid."
- "CYA is high at 98 — consider partial drain."
The service report email
The visit.completed email for pool clients includes the chemistry snapshot, LSI, and any flagged readings. Homeowners love this — most never saw these numbers before.