Hot Tub Water Alkalinity vs. pH

It can often be confusing when looking at a test strip and seeing PH and Alkalinity when in most people’s understanding PH is a reflection of how acidic or alkaline the water is, so below is a brief explanation of the key differences. 

Total alkalinity refers to the concentration of dissolved alkaline substances (mainly bicarbonates, carbonates, and hydroxides) in your hot tub water. It acts as a pH buffer, meaning it helps stabilise the water’s pH and prevents rapid fluctuations (pH bounce). 

• The Ideal Range is 80–120 ppm (parts per million) 
• Keeps pH stable and prevents sudden spikes or drops 
• Low TA means the pH becomes unstable, causing corrosive water 
• High TA means the pH becomes difficult to adjust, leading to scale buildup 

pH measures how acidic or basic (alkaline) your hot tub water is. It is a scale from 0 to 14, with 7 being neutral.

• The Ideal Range is 7.2–7.8 
• Low pH, less than 7.2, means the water becomes too acidic, leading to corrosion, eye irritation, and skin discomfort 
• High pH, greater than 7.8, means the water becomes too basic (Alkaline), leading to cloudy water and scale formation 

Both are important in keeping your water healthy, but you should always balance the TA first and then pH as TA helps keep the pH stable. Keeping your PH stable is important as sanitisers become less effective once the pH moves outside the recommended range. This results in having to use more sanitiser to keep your water clean.