Pool pH & Alkalinity Tips for Pool Owners

Litmus paper for testing pH

Dr. Pool, our resident chemist normally writes our chemical posts however, I’m here today to discuss pool chemistry, in a non-scientific way – no offense to the good doctor!

Here’s some real world pH and alkalinity tips, not from a chemist, but a pool owner, just like you.

The pH balance in your swimming pool is arguably the single most important factor in maintaining clear, comfortable water. A proper pH reading will keep swimmers’ skin and eyes comfortable and will also allow chlorine to do its job most effectively to keep your pool clear and algae-free.

Alkalinity is very closely related to pH; proper alkalinity levels are a key factor in maintaining pH because a low alkalinity level can cause rapid pH fluctuations. Maintaining the proper balance of pH and alkalinity is essential to keeping your pool water in good condition.

pH: a deeper dive

pHpH is a measurement of how acidic or basic the water is. It uses a scale from 0-14, with a pH reading of 7 being neutral. Anything below 7 is considered acidic, while anything above 7 is considered basic.

The pH scale is logarithmic which means that each whole pH value below 7 is ten times more acidic than the next value. For example, a pH value of 4 is ten times more acidic than pH 5, and 100 times more acidic than pH 6. The same is true for pH readings above 7.0.

The ideal range to shoot for in your pool is somewhere between 7.2 and 7.6. Too low and you can have problems, and if the pH gets too high, you have a whole ‘nuther set of problems.

Low pH may cause:

  • Erosion of grout or plaster, or weakening of vinyl liners
  • Corrosion of metals such as ladders, handrails and heat exchangers
  • Complaints of burning eyes and dry skin or scalp
  • Premature breakdown of swimwear and pool floats/toys

High pH may cause:

  • A decrease in the disinfection ability of chlorine
  • Scaling or calcium buildup on pool surfaces/accessories
  • Cloudy or dull pool water quality
  • Heavy chlorine odor and red eyes
  • Clogging of filter media/elements

Alkalinity: a closer look

Total Alkalinity is a measurement of all alkaline substances in the water. A discussion regarding alkalinity can become complicated very quickly (and be pretty boring for those without a degree in chemistry), so the most important thing to understand about alkalinity is that it affects water’s ability to maintain pH levels.

Many describe alkalinity as being a “buffer” for pH. What this means is that if your water has proper alkalinity levels it will be much easier to maintain proper pH levels.  The best range for alkalinity is between 80-120 ppm.

Low Alkalinity may cause:

  • Etching of plaster and leaching of vinyl plasticizers
  • Corrosion of metals in ladders, handrails and heat exchangers
  • Complaints of burning eyes and dry skin or scalp
  • Staining of pool surfaces
  • Rapid fluctuations in pH (known as “pH bounce”)

High Alkalinity may cause:

  • A decrease in the disinfection ability of chlorine
  • Cloudy water; an unsafe condition
  • Difficulty keeping a stable pH level
  • pH increases despite regular addition of pH reducer

If you have any of these issues mentioned above – high or low pH andbalanced-happy-pool-water alkalinity, it is essential that you test your water as your first step. Whether you use test strips, test kits or digital testers – no matter. What’s important is regular testing – balanced water is happy water!

The sooner you detect levels outside the recommended ranges the sooner you can take corrective action, and the less chemicals and effort will be required.

Adjusting Pool pH & Alkalinity

Alkalinity First!” Your pool water’s alkalinity is a buffer for the pH level, so it is important to correct alkalinity imbalances before you attempt to correct pH; this will save you a lot of frustration, time and money spent on chemicals.

alkalinity-increaserIf your alkalinity levels are too low (below 80 ppm), you will need to add alkalinity increaser, which is chemically known as sodium bicarbonate. Be sure to carefully follow dosing instructions, and increase the level gradually in to the proper range of 80-120ppm.

If your alkalinity levels are too high, you will actually add pH reducer, which we sell in a granular form chemically known as sodium bisulfate. There is no product as of right now that is packaged with the label “Alkalinity Reducer”.

Lowering alkalinity levels can be a lengthy, sometimes frustrating process, as sodium bisulfate will also have the effect of reducing your pH at the same time as it lowers your alkalinity. You may need to make repeated adjustments of lowering alkalinity and then raising pH – until both come into proper range.

ph-increaserIf your alkalinity is balanced and you pH still needs adjustment, you will either add pH increaser, which is chemically known as sodium carbonate or soda ash, or pH reducer.

Fixing issues with pH is usually a little easier than alkalinity adjustments – but be sure to follow dosing instructions carefully and make gradual adjustments.

I hope you enjoyed my “Layman’s” discussion on pH and Alkalinity. Questions about how to get your water in proper balance? Leave us a comment below or give us a call at 1-800-288-7946.

Jackie Wolski
InTheSwim Staff Blogger


Pool pH & Alkalinity Tips for Pool Owners — 6 Comments

  1. My 25metre pool is having issues with permanent high pH. Our Alkalinity levels are 80 but we are constantly needing to hand dose acid due to the pH level rising back to 8!
    If we raise our alkalinity any higher then 80 the pool becomes cloudy and the pH rises above 8. Any ideas would be great as its costing me a fortune.

    • Hi, did you have the pool recently replastered? Newly replastered pools have high pH problems for 1 year, and then things return to normal after full curing. Using liquid chlorine as the main sanitizer also contributes to high pH, as the pH of bleach is rather high. You can also use muriatic acid, found in home and hardware stores for around $6 per gallon, or buy larger quantity for less.

  2. Our family just recently bought an above ground pool that holds 1,052 gallons of water. We followed the intrusion for balancing the pool water and after about 2-3 hours we shocked it, covered it for the night and let the pump run. The water is super cloudy. I tested the water using testing strips and it indicates that I now have to much alkalinity and my phone is to low. How can I fix this now?

    • low pH and high alkalinity is a tough one to reverse, as it may take several treatments – using pH decreaser, to lower the alkalinity, which will also lower the ph. Raise the pH again, then lower the alkalinity again, then raise the pH again… pH and alkalinity are close cousins, you can’t affect one without affecting the other. You can also replace some of the water, if your fill water (from the hose) has a better pH/Alk levels. The shock may have also led to the cloudy water. Keep filtering 24/7, and clean the filter cartridge as needed. Small ABG pools often have undersized filter systems, that may require long days of filtering – run it only 8 hours per day, and it may never clear up!

  3. We are constantly struggling to get our ph down. What is causing the ph to always be high. I’ve used ph down but it just goes right back up again

    • Hi Linda, such a great question thank you! First, newly plastered pools have a unique high ph problem for about a year, or the first season. Then it settles down. If that is not the case with you, it could also be a High alkalinity level that is creating resistant to change, buffering the pH too much. If alkalinity is above 120 ppm, lower it with an acid to below 100 or as low as 80 ppm, and you should also see your pH level drop. Finally, there could be a chemical cause, something of a high pH being introduced into the water. Most leaves and dirt, debris etc has a fairly low pH, but some leaves and windblown stuff can be higher. Sodium Hypochlorite, liquid chlorine, has a very high pH of 13, and will require constant pH correction. Most other pool chemicals are fairly pH balanced, with exception to pH increaser, and you wouldn’t be the first person to add pH increaser by mistake, thinking it was some other pool chemical, maybe in the wrong bucket – but now I’m grasping, I’m sure that didn’t happen!

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