February 9th, 2021 by Sarah Miles

Total alkalinity is a metric that we use in hot tubs and pools that helps us keep them well maintained and safe to use. Total Alkalinity, or TA, is the measurement of the concentration of all alkaline substances dissolved in the water.

Total Alkalinity and pH level

There is a direct relationship between TA and pH level – getting the pH level right depends on there being the right level of TA – but TA is not the same as a high (alkaline) pH level. TA is not measured on the pH scale but is measured in parts per million (ppm). The desired level for a hot tub or pool is 80-120ppm. This can be measured with TA test strips.

How does TA help your pH levels?

pH level is important for keeping your hot tub water safe. The desired pH level is 7.4 – 7.6, which is slightly alkaline. This is because sanitisers, such as chlorine, work best in alkaline environments. It’s also the kindest level for your skin and least likely to damage your equipment.

Unfortunately, pH is very sensitive and can be thrown out of balance easily by various environmental factors, such as changes in the water, weather, debris, cosmetics such as body lotion or tanning treatments, bodily substances such as sweat, and even bodily waste (unfortunately, this does happen). TA acts as a buffer for your pH, helping it to absorb fluctuations and generally make it more stable.

There are detrimental consequences of both high and low alkalinity in a hot tub. High alkalinity can cause scaling, cloudy water, and eye and skin irritations. Low alkalinity can cause corrosion of parts and equipment, staining, the greening of the water, and eye and skin irritations.

The importance of checking TA

While TA is more stable than pH, it can still change over time through the same environmental factors listed earlier, as well as incorrect levels of chemicals being used. Periodic checking of TA level is good practice for hot tub owners as the sooner you notice the levels changing, the easier it is to adjust them effectively.

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Getting the TA right

Your TA could be too high or too low and both require you to add chemicals to bring it back to the right level. With both treatments, it is important to add the alkaline increaser or decreaser gradually and keep testing until it’s right. This is another reason why it’s beneficial to test regularly as it’s quicker to adjust it back if the fluctuation is small.

To raise the alkalinity, you can use a hot tub alkalinity increaser product, or you can use standard baking soda (sodium bicarbonate).

To lower the alkalinity, you can use muriatic acid (hydrochloric acid) or dry acid (sodium bisulphate). Once you have the right TA level, it is much easier to both achieve and maintain the right pH level.