maintaining swimming pool alkalinity level
The alkalinity of your swimming pool is arguably the most important water balancing level in your water to manage, and is a must-know item when owning or maintaining a pool. This is why we wrote an article specifically on maintaining swimming pool alkalinity.  Alkalinity is a term to describe how well the water acts as a buffer against changes in pH, and describes how well the water neutralizes acids in your swimming pool water.  To maintain the alkalinity of your swimming pool water, you measure the total alkalinity and adjust this level if necessary.

Clear and Balanced Pool Water All Summer With No Headaches!

We're almost done making an eBook for pool owners like you that want an easy and straightforward guide to keep their pool water balanced and clear with as little work as possible.

Enter your first name and email below and we'll let you know when it's ready!

In this article, I discuss how to successfully maintain the alkalinity of your swimming pool.  You can also read how to test the total alkalinity of your swimming pool water in my article: Testing Swimming Pool Alkalinity.  If you test the level and you need to raise or lower the total alkalinity, read Raising Swimming Pool Alkalinity or Lowering Swimming Pool Alkalinity.

Importance for your pool

Why should you be maintaining swimming pool alkalinity?

You ideally want balanced water in your swimming pool.  The three main tests to check how well you are balanced are total alkalinity, pH, and calcium hardness.  The reason total alkalinity is so important is that you should always test and adjust the total alkalinity first.   Adjusting total alkalinity can affect your pH, and adjusting both of these can affect the calcium hardness level in your water, so you want to test and adjust the levels of each of these in this order:

  1. Total alkalinity
  2. pH
  3. Calcium hardness
You risk adding unnecessary chemicals and waste time testing if you do not balance your water in this order.

The recommended range for total alkalinity in swimming pools is 80 – 200 ppm (parts-per-million), although some pool experts widen the range to 80 – 250 ppm.  This depends things like your local waters source, your climate, and the environment in which your swimming pool is located.

How often do you test your swimming pool total alkalinity?  This level does not change as drastically as pH or the sanitizer level like chlorine or bromine, so you only need to test occasionally.  About once per week is fine, unless you are adjusting the pH or calcium hardness, which you should always test the total alkalinity first and again about 24 hours after adjusting pH or calcium hardness, or after shocking the pool.  I also recommend testing a few days prior to large gatherings to give yourself time to adjust the water beforehand if necessary.

The saturation index is important to mention when discussing total alkalinity, as the saturation index depends on the alkalinity of your swimming pool water.  You can technically have balanced water, as measured by the saturation index, even though your total alkalinity might be a little high or low.  The reason is you also factor in pH and calcium hardness, which slight variations in these values can alter the saturation index without changing the alkalinity of the pool water.

If your pool total alkalinity level is too low (less than 80 ppm).

  • Pool water pH can fluctuate rapidly.Water with low alkalinity does not buffer the changes in the acidity of the water as well.  This can result in pH bounce, where the pH can drop drastically and then spike suddenly, and do this over many cycles.  It is not uncommon for the pH to fluctuate between about 6.8 and 7.8 within a 24 hour time span with very low alkaline water.
  • Concrete pool walls can stain and become etched.Concrete pools are at risk of developing stains in water with low alkalinity.
  • Masonry can etch and dissolve.Masonry such as grout, and stone surfaces can degrade over time, with surfaces that are normally smooth begin to develop grooves, cracks, and have a rough feeling as you pass your hand over them.
  • Plastered surfaces can delaminate.Delamination can occur on plaster, shotcrete, and gunite surfaces.
  • Metal surfaces can corrode.Pool ladders, light housings, hand rails, steps, screws, and other hardware can corrode when exposed to low alkalinity water.  Pump motors, metal pipes, valves, heat exchangers can also corrode.  This corrosion can lead to metals such as copper and iron in the water.
  • Pool wall staining.Vinyl and fiberglass lined pools are also at risk for staining, often due to metal corrosion described above.
  • Chlorine effectiveness is reduced.Chlorine, and other sanitizers such as bromine, are not as effective in water with low alkalinity.
  • Swimmer eyes burn, skin is itchy.Unbalanced water will irritate swimmers in the pool water, as eyes and nasal passages are affected by water with low alkalinity.  Skin will also feel tight and itchy, resulting in an unpleasant swimming experience.

If your pool total alkalinity level is too high (greater than 200 ppm).

  • Cloudy swimming pool water.Pool water with high alkalinity will more easily allow for calcium and other minerals to come out of solution.  These substances will float freely in the water, causing the water to turn murky and uninviting.
  • Water scale on pool surfaces.Water scale can form on pool walls and floors, especially at the surface of the water.  The insides of pool equipment can also become clogged with water scale.
  • Clogged and ineffective filtering.Filters can also clog with water scale, and lose their ability to filter particles while letting water through.
  • Reduced water circulation.Clogged pipes and filters can result in reduced water circulation.  Swimming pools depend on adequate water circulation to filter out contaminates and prevent organics like algae from getting a foothold in the water.
  • Consistently high water pressure.Pool pump motors have to run harder with reduced circulation, resulting in pump wear, seals and gaskets have reduced lifespan, and potential cracks appearing in pipes and valves.
  • pH level hard to change.Changes to acidity and pH are resisted by the high alkaline level of the water.  This almost an opposite effect of pH bounce, where the pH fluctuates rapidly.
  • Swimmer eye irritation, ‘sticky’ feeling skin.Swimmers can be irritated by pool water with high alkalinity as well.

How to Maintain Swimming Pool Alkalinity

There are a number of things to consider in terms of total alkalinity; how to test, what tools and equipment to use, how to interpret the results, and what substances to use to raise or lower the swimming pool alkalinity.

Test your pool total alkalinity level

You should always test the alkalinity level first, unless you suspect your pH might be very low.  In this case, you should test your pH.  If the pH is less than 7.0, adjust the pH upward to 7.0 first.  The reason is excessively low pH will cause incorrect total alkalinity readings.  To test total alkalinity, you need the right equipment, such as test strips, a test kit, or electronic alkalinity tester that can accurately measure swimming pool total alkalinity.

Read more about how to test, lower, or raise your swimming pool total alkalinity:

Interpret the test results, and adjust the total alkalinity level

Once you test your pool water total alkalinity level, you might be within the 80 – 200 ppm range.  If this is the case, you may have to do nothing.  If you are near or have exceeded the low or high limits, then you will need to increase or decrease the total alkalinity.

To increase the total alkalinity in your swimming pool, you typically use sodium bicarbonate, also known as baking soda.  To lower the total alkalinity, you usually use muriatic acid or dry acid.  Dry acid is also called by its chemical name: sodium bisulfate.

Retest total alkalinity

After about 24 hours, you should retest the total alkalinity level in your pool.  It will take about this long for the water to balance to any chemicals you have added.

Conclusion

Maintaining the alkalinity of your pool is relatively easy, as this level does not change quickly, and several products are available to easily test and adjust the total alkalinity.  Keeping your swimming pool alkalinity in-check goes a long way to maintaining a healthy and balanced swimming pool to be enjoyed by everyone.

Source:

  • “Pool & Spa Water Chemistry, A Testing and Treatment Guide, Waterproof Edition, 2005. Taylor”