Glossary
Pool & spa terms explained
- Free Chlorine
- The active sanitizer in your pool, expressed in ppm. Ideal range 1.0–4.0.
- Total Alkalinity (TA)
- Buffers pH against swings. Ideal range 80–120 ppm.
- pH
- Acid/base measure of the water. Ideal range 7.4–7.6 for swimmer comfort and chlorine efficiency.
- Cyanuric Acid (CYA)
- Stabilizer that protects chlorine from UV. Ideal 30–50 ppm. Too high reduces chlorine efficiency.
- Calcium Hardness (CH)
- Calcium concentration in the water. 200–400 ppm protects surfaces and equipment.
- Salt System / Chlorine Generator
- Device that electrolyzes salt into chlorine for saltwater pools.
- VGB
- Virginia Graeme Baker Pool & Spa Safety Act — federal entrapment prevention standard.
- Variable Speed Pump (VSP)
- Energy-efficient pump that adjusts RPM to load.
- Cartridge Filter
- Filter media housed in a removable cartridge, typically rated in microns and square feet.
- Sand Filter
- Filter using graded sand, cleaned by backwashing. Best for high flow with simpler maintenance.
- DE Filter
- Diatomaceous earth filter. Finest filtration but more complex to maintain.
- Acid Wash
- Chemical treatment of bare plaster surfaces to remove staining and scale.
- Plaster / Pebble Finish
- Interior surfaces of in-ground pools. Pebble lasts longer and offers more aesthetic options.
- Skimmer
- Surface debris collector that draws water across a floating weir.
- Main Drain
- Bottom-of-pool suction port; VGB-compliant covers required by federal law.
- Heater Pilot / Igniter
- The start system for gas heaters; common failure point on older units.
- Phosphates
- Algae food source. Levels under 100 ppb dramatically reduce algae blooms.
- Combined Chlorine / Chloramines
- Spent chlorine + organics. High levels cause eye irritation and the 'pool smell'.