Roc Pool Service · Glossary
Pool service glossary
Plain-English definitions for the technical terms you'll see in quotes, water-test printouts, and service reports. Bookmark this when you're comparing bids.
- Free chlorine (FC)
- The chlorine actively available to sanitize your pool. Target range is typically 1-3 ppm. Distinct from total chlorine, which includes spent chloramines.
- Combined chlorine (chloramines)
- Chlorine that has already reacted with contaminants and lost most of its sanitizing power. High combined chlorine causes the "chlorine smell" and eye irritation — the fix is shocking the pool, not adding more chlorine.
- Cyanuric acid (CYA / stabilizer)
- A UV stabilizer that slows chlorine breakdown in sunlight. Too little burns off chlorine fast; too much ("chlorine lock") makes chlorine ineffective even at normal readings.
- Total alkalinity (TA)
- A buffer that keeps pH from swinging wildly. Target range is typically 80-120 ppm. Low TA causes pH bounce; high TA makes pH hard to adjust.
- Langelier Saturation Index (LSI)
- A formula combining pH, alkalinity, calcium hardness, and temperature to predict whether water will corrode equipment or deposit scale. Pros use it to balance water beyond just pH.
- Shocking (superchlorination)
- Adding a large dose of chlorine (or non-chlorine oxidizer) to rapidly destroy chloramines and organic contaminants. Standard practice after a storm, heavy bather load, or algae bloom.
- Green pool cleanup
- The multi-step process of killing algae, clearing dead algae from suspension, and restoring clarity — typically involves shocking, algaecide, extended filtration, and manual vacuuming.
- Winterizing (pool closing)
- Preparing a pool for the off-season: balancing chemistry, adding winterizing chemicals, lowering water level, draining equipment lines, and installing a safety or winter cover.
- DE filter (diatomaceous earth)
- A filter type using diatomaceous earth powder coated on grids for the finest filtration of the three common filter types (sand, cartridge, DE). Requires periodic backwashing and DE recharges.
- Total dissolved solids (TDS)
- The sum of everything dissolved in pool water — minerals, chemicals, and debris byproducts. Very high TDS can cause cloudy water and reduced chemical effectiveness even when individual readings look normal.