Some people believe that keeping the right pH is all that is needed to achieve the correct water balance; this isn’t the case and although pH is important there are other factors that also need to be considered:
pH – The pH scale of 0-14 measures how acidic or alkali conditions are respectively. The middle reading of 7 is neutral, so spa water with a pH below 7 is acidic and spa water with a pH above 7 is alkaline. For Spa users the ideal pH level is slightly alkaline between 7.2– 7.6, ensuring spa equipment protection and bather comfort are maintained (the pH level of the eye is consistent with this level).
Calcium Hardness – Calcium Hardness (or total hardness) is the measure of how hard or soft the water is determined by the amount of minerals (mainly calcium) that are dissolved in the water. This level will vary depending on where your water supply comes from, for example in some parts of Scotland, the water is very soft and in parts of Kent the water can be very hard. If the calcium hardness level is below this range then problems such as corrosive water & staining can occur. However if the calcium hardness level is too high then scale can form on the shell of your spa as well as in the pipework. The ideal calcium hardness level in a spa is 100-200mg/l.
Total Alkalinity – Total Alkalinity (TA) is a measurement of the waters ability to resist pH change. If Total Alkalinity is low then it can make the pH fluctuate, making it difficult to control and mantain at the ideal level. However if the Total Alkalinity is too high then the pH can be difficult to change and will keep rising. A high Total Alkalinity can also lead to a formation of a bicarbonate scale on spa surfaces & within the pipework. The ideal Total Alkalinity level should be between the range of 80-150mg/l.
TDS (total dissolved solids) – Total Dissolved Solids is the sum of everything that is dissolved within the spa water including minerals, chemicals and debris. When the Total Dissolved Solids level is too high problems such as corrosion, poor chemical efficiency & dull looking water can occur. The maximum recommended level is 1,500mg/l. When the level exceeds this it is time to empty and refill the spa.