Managing pH and Total Alkalinity

Maintaining pH within a certain range is important because it can affect plaster, liners, and equipment. Total Alkalinity has NO direct effects on the pool. We care about TA only through its effect on pH and CSI.

Except in a limited number of situations, TA and pH generally move in tandem. If you increase TA, pH generally increases. If you lower TA, pH decreases typically. This article discusses the relationship between TA and pH and how to manage the two.

The primary purposes for looking at the Total Alkalinity and pH relationship are:

• Knowing how to manage Total Alkalinity and pH together because they typically move together and
• Total alkalinity, pH, and their levels and relationship are the number one causes of rising pH/acid demand.

Adjusting pH may impact Alkalinity

PH should be your focus in the relationship between Total Alkalinity and pH. Keep it between 7.0 and 8.0. Let Total Alkalinity be what it may. If you are constantly and frequently adding Acid, then Lower Total Alkalinity. Otherwise, manage pH and ignore TA.

Raising pH

pH rises naturally, and pH will increase without adding any chemicals. pH rarely has to be raised unless you add too much acid to lower the pH or are following the process to lower total alkalinity. pH between 7.0 and 8.0 are satisfactory and need not be raised.

pH is raised the same way that you increase Total Alkalinity. If your pH is below 7.0, the best way to raise pH is through aeration. Aerations will increase pH without affecting TA. Borax is the next best solution, as it will raise pH and have a small impact on TA. Soda Ash/Washing Soda is the next best solution. It will raise pH and increase TA about 2 times the amount that Borax impacts TA. If you find you need to increase pH, and you don't have a way to use Aeration, use Pool Math to help you figure out how much Borax or Soda Ash/Washing soda to add. Baking soda is NOT a good choice to raise your pH. If your pH is below 7.0, then here is the general guidance.

If TA is 50 or above, bring your pH up to 7.4 or so using 20 mule team Borax.

If the TA is below 50, use baking soda to bring it up to 50-60 and THEN raise your pH to around 7.4 using 20 Mule Team Borax.

Lowering pH

pH does not lower naturally. pH only lowers from additions of Acid. If your pH drops, then acid is added to the pool from some outside source, which is rare. Chlorinating tablets can have dry acid and lower your pH and TA. pH is lowered in the same manner as Total Alkalinity is lowered. If your pH is above 8.0, you should lower your pH.

Use Pool Math to determine, given the type of Muriatic Acid you are using, how much Acid to add. It will have a small effect on TA.

Adjusting Alkalinity will affect pH.

Total Alkalinity will not change without external factors. Total Alkalinity will rise with high TA fill water or chemicals. Total Alkalinity will be lower with acid or low TA water. As a general rule, you should NOT force your TA to a specific value or try to maintain a specific value. As long as TA is above 50, let it find its equilibrium with pH

Raising Total Alkalinity

The Alkalinity of pool water is raised in several ways, primarily by adding an Alkaline agent. Depending on what you use, it will have varying effects on pH. This table shows how pH changes when you raise TA by ten ppm.

Baking soda has a small impact on pH and is the preferred method for increasing TA. If you need to raise your TA and decide to use Washing Soda or Borax, understand that it will raise your pH somewhat significantly.

Lowering Total Alkalinity

The Alkalinity of pool water is lowered using Acid. Adding Muriatic acid is the best way to reduce your TA because alternative acids add other chemicals to your pool or negatively impact you or your pool. Dry acid should not be used in plaster pools or pools with a SWG. Adding acid lowers your TA, but it also lowers your pH. This table shows the effect of lowering TA by ten ppm on pH.

The higher the TA, the more rapidly the pH will rise over time.

Chemical	TA decrease	Associated pH decrease
31.45% (20 Degree Be) Muriatic acid	10 ppm	.6 decrease

This significantly impacts pH! Assume your 5000-gallon pool has a TA level of 120. You look up the recommended levels for your pool and determine that your pool should have a TA of 80. If you add .4 Gallons of 31.45% Muriatic acid to reduce your TA by 40, you will CRASH your pH by an astounding 2.5. Lowering TA should be done in stages described here Lower Your TA.

Can I change one without affecting the other?

Can I raise pH without affecting TA?

Yes, Aeration

Can I lower pH without affecting TA?

You cannot directly lower pH without lowering TA, as Acid (used to lower pH) also lowers TA. You can, however, reduce pH with acid, then add baking soda to raise TA back to the same level as the TA level where you started. This chart shows how to lower pH by .5 with acid and use Baking soda to restore TA. (amounts will vary by pool; use Pool Math to determine the correct amounts!)

Chemical/Action	pH decrease	Associated TA change
31.45% (20 Degree Be) Muriatic acid	.5	8 ppm Decrease
Baking Soda	0	8 ppm Increase

Can I raise Total Alkalinity without affecting pH?

Practically? Yes, use Baking soda. You can add up to about 20 ppm of TA using baking soda while changing pH <.1. Larger additions of baking soda will have at least a .1 increase in pH. As an example, 80 ppm TA addition of baking soda would raise pH .2. If you need to raise TA more than ~20ppm, add 20 ppm baking soda, allow it a period of time to circulate, correct pH if necessary, then add additional doses (<20ppm) and adjust pH, until you hit your target TA.

Can I lower Total Alkalinity without affecting pH?

No and Yes. If you use this process, you will end up with the same pH but lower TA: Lower your TA. However, you will change pH many times while you are lowering TA.

Causes and reducing pH rise

Causes of rising pH

The aqueous (dissolved) CO2 level in pool water determines how fast pH will increase. Many pool owners experience constant acid demand, and pH rises quickly, requiring constant acid additions. There are several causes of high levels of CO2, rising pH, and acid demand:

1. Water features and aeration release CO2
2. Lower pH water has higher levels of CO2
3. Higher levels of TA allow higher levels of CO2
4. When pool water has low pH and high TA, it has the most amount of stored CO2

For a deeper dive into the chemistry, start here: PH TA Relationship

Reducing pH rise and acid demand

Turn off Water Features

Water features and aeration cause the release of CO2, which raises pH. The ways to combat this are to turn off the aeration or limit the time the water feature runs.

Cover your pool

A solar cover will drastically reduce the release of CO2.

Reduce your Total Alkalinity level

Practically, as pH rises, the rate of rise will slow. If the pH rise is faster than you care to maintain, reduce your TA until the rate of rise is reasonable to manage. There will become a point where the TA is sufficiently low, and your pH will slow to a reasonable level.

A reasonable starting point for most pools is a TA of 80-100. Most find, however, particularly with SWCG pools, that a TA of 60-80 slows their pH rise sufficiently, hence the TFP recommended levels. TA can be safely lowered as far as 50 ppm if necessary. The TA range in the Recommended Levels protects your pool surface if the pH, TA, and CH can be kept in the recommended ranges.

The scope of this article is to help you better manage Total Alkalinity and pH together. It will not get you to a permanent, zero-acid demand pool. It will significantly extend the period between acid additions.

Other Questions

If TA in the water contributes to pH rise, can I just get rid of all the TA?

TA levels below about 50 ppm lead to insufficient TA to buffer pH to prevent sudden pH crashes.

Can I ignore my Total Alkalinity lever if my pH is steady?

No and Yes. No, because you should perform regular testing to ensure TA doesn't go below 50. Yes, because you now understand the relationship between TA and pH and that one of the primary objectives of TFP is to have a pool that has reasonable rising pH levels and acid demand. Once your pH rise is manageable, you have met the objective. Your pool is in reasonable equilibrium. Sit back and enjoy!