Water chemistry is every pool owner’s favorite subject, right? Maybe not. Many people cringe when a conversation about pH and alkalinity in swimming pools arises, and we get it! It’s definitely not the most glamorous or interesting topic, but like it or not, pH and total alkalinity play an important role in keeping your swimming pool clean, clear, and safe for swimmers. 

pH vs Alkalinity

Pool owners often get confused about the difference between pH and alkalinity level. Simply put, pH is the measure of how acidic or basic a substance is. The pH scale ranges from 0-14, with 7 being neutral. Substances with a low pH level are more acidic, while those with a high pH are more basic, or alkaline. The ideal pH in a pool is 7.4-7.6.

Total alkalinity is very closely related to pH, and it is a measure of all the alkaline substances in the water. The simplest way to think about alkalinity and how it relates to pH in pool water is that total alkalinity affects your water’s ability to maintain proper pH levels. In other words, alkalinity acts as a buffer for pH. When alkalinity levels are in the proper range, pH levels are more stable. The proper total alkalinity in a pool is 80-120 ppm.  

Why Do Pool pH and Alkalinity Matter?

The laundry list of problems associated with improper pH and alkalinity levels in pools is long, and it’s not pretty.

Effects of Low pH in Pools 

  • Red, burning eyes and dry, itchy skin
  • Grout or plaster erosion
  • Vinyl pool liners become brittle and stiff
  • Corrosion of the metal on fixtures such as lights and ladders and in pool equipment
  • Damage to pool floats and toys

Effects of High pH in Pools

  • Cloudy water
  • Increased algae growth
  • Decreased effectiveness of chlorine
  • Scaling, or calcium buildup on pool surfaces
  • Strong chlorine odor and red, itchy eyes

Effects of Low Total Alkalinity in Pools

  • Rapid changes in pH
  • Etching and/or staining of pool plaster
  • Vinyl liners become brittle and stiff
  • Corrosion of the metal on fixtures such as lights and ladders and in pool equipment

Effects of High Total Alkalinity in Pools

  • Cloudy pool water
  • Decreased effectiveness of chlorine
  • May be difficult to lower pH, even with the addition of pH decreaser

How to Determine Pool pH and Alkalinity Levels

The only way to find out if your pool water’s pH and alkalinity are in the normal range is by testing the water regularly. Use a test kit or test strips to check your water chemistry at least once per week during swim season. Adjust alkalinity and pH first, then add other pool chemicals accordingly to adjust bromine or chlorine levels, calcium hardness, etc.

Common Pool pH & Alkalinity Problems

When balancing your water chemistry, always be sure to adjust the alkalinity before you try to adjust pH. This will save you lots of valuable time and money. After making adjustments to alkalinity, always retest the water so that you can see what changes have occurred in alkalinity and pH.

High Pool Alkalinity

When you need to lower alkalinity in your pool water, use a product like No Mor Muriatic Acid, or Doheny’s pH Minus. These granular products are safe to use and will bring down both pH and alkalinity.

Low Pool Alkalinity 

When the alkalinity level in your pool is low, use sodium bicarbonate (baking soda), which is an alkalinity increaser. Try Doheny’s Alkalinity Up.

High Pool pH

A high pH reading in pool water is common in saltwater pools and pools that use liquid chlorine sanitizer. Newly installed pool plaster or pebble finishes can also raise pH levels in swimming pool water for the first year. To bring the pH down, use sodium bisulfate, or dry acid. Try Doheny’s pH Minus.

Low Pool pH

When your pool’s pH is low, this is most often caused by using chlorine tabs or other forms of stabilized chlorine that contain cyanuric acid. Low pH can also be caused by heavy rainfall or excessive debris in the water. To bring pH up, use sodium carbonate, also known as soda ash. Try our pH increaser, Doheny’s pH Plus.

Low pH and High Alkalinity

When you have low pH and high alkalinity, here is a pretty easy trick to fix it. First, use pH Minus to bring down both the pH and alkalinity, then raise the pH only with aeration. Aeration just means adding air to the water. When you aerate your pool water, carbon dioxide in the air mixes with water to form carbonic acid, thus increasing the pH level. You can aerate your pool water with an air compressor, by installing a pool fountain, or by pointing return jets upward to create surface agitation.

High pH and Low Alkalinity

When you use Alkalinity Up to increase alkalinity, pH levels will also increase. This is bad news if your pH is already high. In order to increase alkalinity more than pH, use a simple trick called the bucket trick. Add Alkalinity Up to a bucket of clean water and place it on the floor in the shallow end of the pool or in an attached hot tub. Leave it there for several hours with the pool pump turned off. This trick also works with pH Minus, when you are trying to decrease alkalinity more than pH.  

Maintaining the normal pH and alkalinity levels in your pool is a very important part of your pool maintenance routine. Proper pH and alkalinity levels help your sanitizer work effectively and protect pool surfaces and equipment. If you have any questions about how to adjust the pH and alkalinity in your pool, please contact Doheny’s today at 800-574-7655 or visit us online at doheny.com.