Chemical Concentration
You should always use the correct quantities of chemicals for your pool size. To work out the water capacity of your pool (in gallons), you can use the following formulas:
Imperial (gallons):
- For square or rectangular pools – length (ft) x width (ft) x average depth (ft) x 6.25 = volume (gallons)
- For circular pools – 3.1428 x radius2 (ft) x average depth (ft) x 6.25 = volume (gallons)
Metric (m3):
- For square or rectangular pools – length (m) x width (m) x average depth (m) = volume (m3)
- For circular pools – 3.1428 x radius2 (m) x average depth (m) = volume (m3)
Pool pH
All pools should have a pH between 7.2 and 7.6. A low pH is acidic and corrosive and will damage pool parts and sting the bather’s eyes. A high pH is alkaline and stops any chlorine present from working as well as being scale forming.
Test the pH of your pool using Phenol Red in a test kit. If your pool pH is not within the required limits (either too high or too low), you can add a pH minus or a pH plus to bring levels within the required limits.
- pH minus – A pH above 7.6 (‘high’) is lowered by adding pH minus (sodium bisulphate or pool acid)
- pH plus – A pH below 7.2 (‘low’) is raised by adding pH plus (sodium carbonate or pool alkali)
