February 5th, 2021 by Sarah Miles

5 things you may not know about Total Alkalinity

Total alkalinity, sometimes called TA, is the measurement of all alkaline substance dissolved in the water. Even if you’re new to hot tubbing, you probably know about balancing pH, which involves adding acid and alkaline substances to keep your water pH neutral. Confusingly, this isn’t the same thing as total alkalinity! However, the two are related, and they’re very important when keeping your hot tub healthy.

This quick primer will explain the link between total alkalinity and pH, and why it’s important.

1. Total alkalinity gives pH stability

pH is very sensitive and can easily fluctuate whenever anything enters the water. That includes things that wash off your body (such as makeup, deodorant, skin oils, sweat, and so on), as well as rainfall, bits of dirt, and leaves. Total alkalinity acts as a buffer – it lets your water absorb some acids, so your pH levels remain much more stable.

2. Total alkalinity first, then pH

Because total alkalinity is the stabilising factor, it’s important to get this right first and then move on to your pH levels. This makes balancing the pH level much easier. If your total alkalinity is wrong, you can expect to chase that pH level up and down as it’ll be very volatile.

3. Why hot tub water should be slightly alkaline

The ideal pH level for your hot tub water is 7.4-7.6, which is slightly alkaline. This is because chlorine works best at this level. Chlorine is a sanitiser which prevents bacteria from forming, keeping your water – and, more importantly, you – healthy.

4. The consequences of high or low alkalinity

There are detrimental consequences to both high and low alkalinity that need to be taken seriously; for maintaining your equipment, for the enjoyment of your hot tub, and for health reasons.

While the water should be slightly alkaline, and high total alkalinity is preferable to low, if it’s too high it can make the water cloudy, cause scaling, and irritate eyes and skin. It will also inhibit the sanitiser, which could compromise health.

Even worse, low alkalinity is detrimental as well. Acidic water can corrode metals, cause staining, make the water go green, and cause skin irritation.

5. How to balance total alkalinity

If your total alkalinity is too high or too low, you will need to adjust it back to the desired level. In simple terms, you add alkaline or acid as appropriate to bring the level back to within the desired range. For high alkalinity, add muriatic acid or dry acid. For low alkalinity add a hot tub alkalinity increaser product or sodium bicarbonate.

In both cases, you must add a small amount, leave it to work and then test again. Repeat this process until it reaches the desired level. It can take days or even weeks to get it right so be patient. The more often you monitor the total alkalinity, the easier it will be to maintain a safe level.