High PH in Hot Tubs

In a hot tub, pH is a very important aspect of water balance. It determines whether hot tubs are too acidic or too scale forming. High pH is a reoccurring issue for many hot tub owners. When a pH is too high in a hot tub, the water becomes scale forming . High pH can cause premature equipment failure and increase your sanitizer consumption.

What causes high pH in my hot tub?

The primary reason for a high pH and the tendency for the pH to stay high is a very high total alkalinity. Total alkalinity is the buffer to keep pH in range. If the total alkalinity is not in range, it cannot buffer the pH to stay in the desired range for hot tubs. Hot tubs in particular generate a lot of bubbles and tend to have higher temperatures. This combination creates a gas called carbon dioxide very quickly. Carbon dioxide builds up and makes the pH go up. This is why hot tub owners, on a regular basis, need to add something to lower their pH and alkalinity. Hot tubbers that have an even harder time lowering their pH is are ones that have well water for the source water – softened or straight from the well, it generally has a high pH and total alkalinity.

scale from inside pipes

What is scale?

The effect that high pH has on hot tub water is that it is very scale forming. With the combination of high temperature, high pH and even an ideal or low calcium, it can cause white chalky deposits to form on hot tub surfaces. This can be a feeling of sand on the acrylic surface of the hot tub. Hot tub owners may also notice white flakes coming out of their hot tub jets. These flakes may get caught in the filter and plug it. This prevents good water circulation in the hot tub and can create flow error problems. Scale can also form on the insides of plumbing and on the heater’s surfaces. This can cause blockage in the plumbing and prevent proper water circulation in the hot tub or breaker tripping/heater element failure respectively.

scale on heater element

How to lower pH in a spa

In order to lower pH effectively, hot tub owners must be consistent in adding pH minus to their hot tubs. A product that is used to lower pH is sodium bisulfate. Sodium bisulfate is solid dry crystals which is a dry acid. Acids are used to lower pH into the recommended range for hot tubs which is generally between 7.4-7.6. When adding pH minus, hot tub owners should not add it all at once. The recommendation is to add a designated amount each day until the pH has come down. If pH minus is added too quickly the water will turn too acidic and will need to be brought back up. If pH will not lower after adding the recommended amount of pH minus, hot tub owners can always add a liquid acid which can be more aggressive at bringing down a pH. Chances are the pH is much higher than the actual reading on the test strip. If this is the case, the hot tub owner must continue to add pH minus until the pH is brought down to normal levels.

The real key to problem solving a high pH challenge in your hot tub is to partner with your local hot tub care professional. Take advantage of any free water testing offers they have and use their expertise and advice to make your hot tub care simple as 1-2-3!


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