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How and Why You Need to Balance the pH of Your Pool or Hot Tub Water


Chlorinating and brominating products work best in water that is properly balanced.  Balanced water is also more comfortable for swimmers and helps to extend the life of the equipment.  pH is the primary factor in balanced water. Let's talk about why that matters and what to do about it. 

What is pH?

pH is a number that characterizes the acidic or basic characteristics of a liquid substance.  Measured on a scale from 0-14, acidity and basicity are opposites on the pH scale with seven being neutral.  The pH number represents… the negative logarithm of the hydrogen  ion concentration.

Understand it this way; the negative logarithm stuff simply means that there is an inverse relationship (if one is high, the other is low) between the pH number and the amount of potential Hydrogen ions… The more hydrogen ions there are in a solution, the lower the pH is

What the Pool / Spa Owner Wants to Know About pH

A typical pool / spa owner only wants to know things that affect their use of the product.  So what are the features of water with a proper pH?  What are the benefits of these pH features?

  • Swimmers are more comfortable.
  • Water remains more clear.
  • The pool/spa equipment and surface last longer and perform better.
  • The sanitizers in the water work more efficiently.

Acceptable pH range: 7.2 to 7.6 (Ideal 7.4 to 7.6)

Swimmer Comfort

If pH is too high or too low, the water could feel uncomfortable to swimmers.  As a matter of fact, an improperly balanced pH causes most complaints of itchy or irritated skin and burning, blood-shot eyes.  What chemical is typically given the rap for these water characteristics? The answer is chlorinating products. Now we know chloramines do pose some discomfort to bathers but a pool or spa owner that performs proper maintenance minimizes this discomfort.

Water Clarity

Generally speaking, a high pH will promote cloudy water and a low pH will promote clear water.  As a matter of fact, low pH is a huge problem because the water does not give the owner any visual clue that there is a problem.  After all, the water is sparkling clear, and that’s what they wanted.  They think, “If it looks good, then it must be good.” This low pH is not only eating away at the swimmers, it is also eating away at the pool and equipment.  It is only a matter of time before major expenses are incurred as a result of the corrosive nature of a low pH.   A high pH is typically handled more quickly because the water will begin to cloud.  This visual clue will prompt pool/spa owners to do something because they know they have a problem.

Surface and Equipment Longevity

Corrosion: The eating away of metals and surfaces (caused by low pH).  This leads to costly replacement of things like: handrails, lights assemblies, the plaster surface, the vinyl liner, pump impellers and seals, and heat exchangers. These problems can be prevented by maintaining proper pH.

Scale:  A mineral build-up, especially calcium, that forms on surfaces and reduces equipment efficiency.  Scale formation on the surface is unsightly and uncomfortable to walk or sit on.  Scale formation in the plumbing, filter and heater ultimately cost the owner money.  Circulation is choked off from scale formation in the plumbing.  Filtration is impossible when the filter media is clogged with scale, ultimately resulting in cloudy water.  All of these conditions can be prevented.

Sanitizer Efficiency

Of the three primary sanitizers we have discussed (chlorinating products, brominating products, and biguanide), chlorinating products are the most vulnerable to an improperly balanced pH.  Simply put, when the pH is below 7.2, the activity of chlorinating products increases to such an accelerated rate that the HOCl residual leaves the water prematurely.  When the pH is above 7.6, the amount of HOCl is reduced to the point where it cannot provide adequate sanitizing opportunity to the water.  In either case, more HOCl is required to compensate for the inefficiency that the pH is causing.  Brominating products (HOBr) are more tolerant of the pH, maintaining adequate sanitizing effectiveness in a wider pH range.   Biguanide (PHMB) sanitizing effectiveness is not as adversely affected by pH swings one way or the other.  However, the effectiveness of the sanitizer is only one of four reasons to monitor the pH.

How to Balance Your pH

Balancing the pH of your pool or hot tub water is really quite simple. However, in some cases it can present a few challenges.

pH can be affected by the dissolved solids, or minerals, and other trace chemicals in your water. The mineral content of your source water will vary depending on your location. Ideally, your water will have some mineral content but won't be too high in certain minerals like calcium.

In the majority of cases your source water will be just fine and fall within normal mineral parameters. From here you will simply need a test kit or test strips and 2 bottles of chemicals, a pH increaser and pH decreaser. If you have a liquid test kit, measure your water following directions. You will likely have to add a certain number of drops of each of the prescribed chemicals to get specific readings. Test strips, on the other hand, are even more simple, but a little less precise. Simply test your water and compare the colors of the reactive areas to the baseline colors on the bottle to get a reading. Of course test strips are not ideal for those with color blindness.

Maintain your pH from 7.2 to 7.6 by adding the appropriate level of pH increaser or decreaser for the volume of water you are maintaining. You will of course have to also add sanitizer as needed. If your pH is balanced your sanitizer use should decrease.

If you find it challenging to maintain your pH you may have an issue with your source water chemistry. In these rare cases it's best to work with a local professional at your pool or hot tub store to initially set up your water according to their recommendation. Many hot tub and pool stores will offer water testing that will help them give you specific recommendations.

Maintaining your water in proper balance is actually quite easy. Set up a reminder on your calendar and perform a quick check at regular intervals and you should be able to rest easy with perfectly balanced water.