Are you trying to get a handle on pH?
This is a complete beginner’s guide to pH in your pool, what it means, why it’s important, how it works, and how to adjust it.
Quick answer: Your pH level indicates how acidic or basic your pool water is, impacing everything from chlorine effectiveness to water clarity. Keeping your pH level between 7.2 and 7.8 is recommended.
What is pH?
pH, or potential of hydrogen, represents how acidic or alkaline (basic) your pool water is based on how much hydrogen is in the water.
It’s measured on a scale of 1 to 14. A reading of 1 is extremely acidic with a high concentration of hydrogen ions in the water, while 14 is extremely basic with a low concentration of hydrogen ions.
To put this in perspective:
- Lemon juice has a pH level of 2 (very acidic)
- Urine has a pH level of 6 (acidic)
- Tap water has a pH level of 7 (neutral)
- Seawater has a pH level of 8 (alkaline)
- Bleach has a pH level of 13 (very alkaline)
Fortunately, pool water almost never goes to such extremes. In fact, most swimming pools will settle closer to neutral (pH 7), and very rarely below a pH level of below 6 or above 9.
Why is pH Level Important?
Your pH level is important because it fundamentally impacts the chemistry and overall quality of your pool water.
This is best described in ways your pH can work against you:
It Can Damage Your Pool
When your pH level gets too high, it causes calcium to precipitate and deposit itself along your pool surfaces. This makes your water cloudy and leads to a problem known as calcium scaling.
Not only does scaling ruin the aesthetic of your pool, but a buildup of scale in your plumbing will also put a strain on your filter system, leading to circulation issues and even potential equipment failure.
When your pH level gets too low, the water can become corrosive, eating away at plaster, metals, grout, and even pool tiles (this is called etching). Even vinyl liners become faded, weakened, and more prone to tearing.
It Messes With Your Chlorine
Chlorine is less effective at higher pH levels, which means your normal chlorine level may no longer have enough “sanitizing power” to deal with contaminants like bacteria, viruses, and algae, even if it usually would be.
This soon leads to your water becoming murky or cloudy, and eventually green once algae begin to flourish.
By the same token, lower pH will significantly increase the effectiveness of your chlorine, but the benefits of it simply aren’t worth the consequences of making your water more corrosive.
It Can Cause Irritation
A pH level that’s too high causes dry, itchy, or “sticky” feeling skin, and sometimes even skin rashes. It also irritates the nose and eyes, similar to the feeling of getting shampoo in your eyes.
A pH level that’s too low has a similar effect in terms of skin irritation, stripping the natural oils from your body and leaving you with dry, itchy skin. It also causes more severe eye irritation, such as redness, puffiness, and burning.
Even then, aside from causing slight discomfort, it would require an extreme pH shift for a pool to be considered too dangerous for swimming.
What is the Ideal pH Level?
The ideal pH range prevents both corrosive and scaling conditions in your pool while also allowing chlorine to work effectively.
This range happens to be slightly basic at somewhere between 7.2 and 7.8.
Some pools will naturally settle at the lower end of that range, while other pools will be better suited at the higher end.
Nobody can tell you what that number is for your specific swimming pool, but it’s something you will slowly begin to identify as a test and observe your pH level over time.
What is a pH Buffer?
In the context of pool care, a pH buffer helps to stabilize the pH and keep it balanced in the long term.
Total alkalinity is your primary buffer. It serves as a kind of shield for your pH level, absorbing changes in the water (mostly acids) before they have a chance to significantly impact (mostly lower) your pH.
Typically, you’ll want to keep your total alkalinity between 80 and 120 parts per million to ensure your pH has a suitable buffer.
Borates, in the form of Borax or boric acid, also buffer pH. Unlike total alkalinity, borates are more effective at buffering against a pH increase and are considered optional in terms of pool maintenance.
Finally, cyanuric acid is a pool stabilizer but it works to stabilize your chlorine against the sun’s UV. Despite the similar name, it has nothing to do with stabilizing your pH level.
How Does pH Influence Other Levels?
The pH of your water doesn’t actually change any other level in your pool, it only changes the behavior and effectiveness of those levels
For example, pH directly dictates how effective your chlorine is at dealing with contaminants. A higher pH weakens your chlorine’s sanitizing power without any change in your chlorine level, and a lower pH directly strengthens it.
Another big one is your calcium hardness level. The calcium content dissolved in your water doesn’t change when your pH changes, but it does change how much calcium your water needs.
Water accepts less calcium at higher pH, which causes calcium to precipitate out of the water. This results in calcium scaling or white flakes that form on your pool surfaces and equipment.
At low pH, pool water becomes corrosive as it tries to seek out more calcium wherever it can, leading to etching. While your calcium hardness level remains unchanged, it’s no longer enough to achieve balance in the water.
Finally, the buffering effect provided by your total alkalinity is diminished at high pH levels as it can’t absorb acids as effectively. While only subtle, this takes some stability away from your pH.
What Causes pH to Change?
A ton of things influence the pH level in your pool, both directly and indirectly.
Let’s cover the main offenders.
The Common Causes of Rising pH
Typically, a pool’s pH level will slowly rise over time.
This happens because of a process called outgassing, where carbon dioxide leaves the water as it tries to equalize with the surrounding air (a bit like when you open a can of soda).
Having high total alkalinity will also create a large pH buffer. This absorbs most acid in the water and prevents it from lowering your pH level.
You can’t overlook algae, either, as it removes carbon dioxide from the water during photosynthesis. Since carbon dioxide is acidic, this natural process of removing it from the water will slowly raise the pH level in your pool.
There are plenty of ways to directly increase your pH as well, including using a pH increaser (soda ash), alkalinity increaser (baking soda), or even some types of chlorine such as calcium hypochlorite (pool shock).
The Common Causes of Falling pH
In some cases, the pH level in your pool will decline over time.
This can happen when adding any type of acid to the water, such as muriatic acid (hydrochloric acid) or sodium bisulfate (dry acid), as well as some types of chlorine such as trichlor (usually tablets).
In high enough volume, even things like rainwater can lower your pH level over time because it’s slightly acidic.
Similarly, if your total alkalinity is low, your pH will lack the buffer it needs to resist those changes in the water, allowing small amounts of acid to have a measurable impact on your pH level.
Organic contaminants such as leaves, insects, and bather waste also work to lower your pH level. This is because, when they decompose in water, it produces an organic acid that slowly chips away at your pH.
How Do You Test the pH Level?
You can test your pH level with almost any pool test strip or liquid drop testing kit out there, assuming it’s not a specialized test.
With that being said, liquid test kits are considerably more accurate than strips regardless of what you’re testing for, but they’re also more time-consuming and more expensive to use.
If possible, get a liquid kit like this one from Taylor, and learn how to use it properly. This uses reagents and will give you a much deeper insight into your pH and how it responds to influences in the water.
Otherwise, even without pinpoint accuracy, a test strip will give you a good enough reading to work with. It works by simply dipping a strip into the pool and waiting for the color to change.
Testing should be done as often as daily at first, eventually reducing it to once or twice-weekly once you start to identify a reliable pattern.
How Do You Adjust the pH Level?
Once you’ve tested your pH level to get your starting point, adjusting it is simply a case of adding the right substance.
What you need to add depends on whether you’re going up or down in pH.
How to Lower Your pH Level
Most pool owners use muriatic acid; a liquid acid that’s poured directly into the water. Aside from being extremely effective at lowering the pH level, it’s also widely available in most regions and relatively inexpensive.
The second most common type of acid used for lowering pH in a pool is sodium bisulfate, also known as dry acid. As its name suggests, this is a dry form of acid that’s easier and safer to handle, but it does add sulfates to your water.
The amount of acid you will need to use depends on the type of acid you choose, as well as your starting and target pH. Your dosage may also vary if your total alkalinity is too high or too low.
How to Raise Your pH Level
The go-to substance is usually washing soda (soda ash or sodium carbonate). The powder is dissolved in a bucket before being added to the water, and it’s very effective at raising both pH and total alkalinity.
If you need to increase pH with minimal impact on alkalinity, Borax (sodium borate) is a better choice. This household product can be directly added to the water for a quick pH adjustment.
As before, your dosage will vary depending on the product you’re using, your starting and target pH level, and your current total alkalinity.
How Do You Maintain Your pH Level?
Knowing how to adjust your pH level is one thing, but being able to maintain it afterward is where the real efficiency is.
It takes time to truly understand how your pool’s pH level reacts to changes in season and usage, so you’ll need to test your water regularly and consistently to gain a firm grasp on this relationship.
For example, if your pH level tends to rise over time, consider adding a regular dose of muriatic acid into your maintenance routine. Conversely, if your pH tends to drift south, you may need to evaluate your chemical usage.
Your total alkalinity is also your best defense against fluctuations in pH, so testing and ensuring your alkalinity stays between 80 and 120 parts per million is equally as important.
Finally, the general upkeep of your pool will go a long way here. Things like regular cleaning, using a pool cover, and maintaining a high enough sanitizer level to prevent algae will reduce the influence on your pH.
The Bottom Line
Your pH level is at the heart of your pool chemistry, dictating how your water looks, feels, and even its ability to fight off contaminants.
Keeping your pH in the range of 7.2 to 7.8 is where everything clicks, using various substances like muriatic acid, soda ash, and borax to dial it back in when it starts drifting off course.
Maintaining your pH is best achieved by simply maintaining your pool, through regular testing, monitoring and adjusting other levels such as total alkalinity, and taking steps to minimize contamination.