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How to Lower pH in a Pool

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  • 01-01-2019
How to Lower pH in a Pool

"pH" is an abbreviation for "power of hydrogen" or "protons hydrogen"; it measures the amount of hydrogen ion in the water and pool water. It affects the level of maintenance needed as well as the comfort of the swimmers. The pH scale is such that the higher the pH, the more alkaline the solution while the lower the pH, the more acidic the liquid is.

What happens if the pH level gets too high?

pH level can increase due to many reasons, first of which is adding chlorine stabiliser or HTH granular into the pool water. The chlorine in these products disinfects the water but also raises the pH level. Another cause of an increase in pH is a sudden rise in water temperature. 

The increase in pH will cause the chlorine in your water to be less effective which will, in turn, drain your pockets since you will have to add more chlorine in the pool water. Secondly, the acidic water will have an adverse affect on the user's skin, including symptoms such as red eyes, dry skin and equipment wearing prematurely, including the goggles and swimsuit.

What is Alkalinity?

Alkalinity is the dissolved salts such as carbonates which help to stabilise the pH. As a result, you can easily maintain the levels of pH and chlorine levels when alkalinity lies in the right range. Lowering alkalinity requires adding of muriatic acid which also reduces the pH. 

On the other hand, raising alkalinity needs adding sodium bicarbonate or baking soda. You should note that it is different from sodium carbonate (soda ash).

artistic view of water splashing

How to lower pH level

If your pool's water pH level is above 7.6, you can lower in due time using pH Minus, which is an acid that will reduce the pH level. pH Minus is available in powder form, and you must first dissolve the granulate in a bucket full of water before spreading it on the water surface. Such action helps to protect the lining against any damage that the acid can cause. The correct amount of pH Minus you should add depends on the current pH level and the total volume of water. It comes with a schedule in its packaging which you can use to determine the right dose for lowering the pH.

  Water Volume (gal)
 pH 1000 5000 10,000  15,000  20,000  25,000  50,000 
 7.6-7.8 1 1/4 oz. 6 oz. 12 oz. 18 oz. 24 oz. 1 qt. 2 qts.
 7.8-8.0 1 1/2 oz. 8 oz. 16 oz. 24 oz. 1 qt. 1 1/4 qts. 2 1/2 qts.
 8.0-8.4 2 1/2 oz. 12 oz. 24 oz. 1 1/4 qts. 1 1/2 qts. 2 qts. 1 gal.
 Over 8.4 3 oz. 16 oz. 1 qt. 1 1/2 qts. 2 qts. 2 1/2 qts. 1 1/4 gal.

If your pool water pH reading is 7.8 and above, and it is an average size in-ground pool holding around 15,000 gallons of water, you should use a quart or ¼ gallon of muriatic acid. You should then allow the water to recirculate for about an hour and re-test it. 

On the other hand, if your pool is above ground or smaller in size, then you can start adding a cup of acid, re-test and keep adding more until you achieve the right pH. For a spa, you do not need too much acid, therefore, use only a cap and add more if need be.

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