When doing or learning about swimming pool chemistry, the second most common term that you will hear about is “pH”.
Most people have no idea what pH is. They just hear or read that it’s important so they are constantly trying to keep it within range and then blaming it on green, cloudy, or algae-ridden pool conditions.
The acronym “pH” for swimming pool water is most commonly short for “potential of hydrogen”. The proper range for pH in pool water is 7.2-7.8. The main reason for maintaining a proper pH is to allow a sanitizer (chlorine) to properly work at sanitizing and oxidizing.
6 FUN (AND MAYBE HELPFUL) FACTS ABOUT PH IN POOL WATER
1. The term pH is short for “potential of hydrogen”. I know. This doesn’t help you at all. Lol
2. Everything has a pH
Chocolate and vinegar
Dog and Cat skin
5.5 - 7.5
Freshly fallen Oak leaf
5.0 - 5.5
4.6 - 8.0
3. There is a relationship between pH and TA (total alkalinity)
4. pH in above-ground pools typically stay lower than in concrete pools
5. Rainwater can lower a swimming pool’s pH, but usually only temporarily
6. I have adjusted the pH in my personal pool and my neighbor’s pool only about two times over the last 10 years.
THE RELATIONSHIP BETWEEN CHLORINE AND PH
This can be one of those things that are so complicated that even Bill Nye the science guy would lose interest. Chemistry is not the exact science that people think it is. Get a couple of chemists together and you’ll see how much variation there is in the interpretation of the data.
In truth, you can take care of your pool perfectly for a lifetime and not have to know about the relationship between chlorine and pH. However, it may help those who can’t seem to stop trying to adjust their pH every five minutes.
Chlorine works best as a shock (adding a lot of sanitizer in a very short period of time) when the pH of the pool is lower. So, if your pool is green or cloudy due to no chlorine, then when you shock it, lowering the pH will help the chlorine work better at mass killing.
FOR EXAMPLE: During my years of having a pool maintenance business, I specialized in bringing green pools back to clear.
When I came across a super green pool, I would check the chlorine level and the pH reading. Usually, the chlorine was at zero and the pH was high(8.0+). I would then pour in 5-10 gallons of liquid chlorine (2-4 yellow jugs) AND a half gallon or so of muriatic acid.
I poured in the acid to temporarily lower the pool’s pH so all that chlorine I just added will work well as a shock (global killer).
I would then come back in a couple of days and test again. Hopefully, the chlorine level would be at zero so I could shock again. At that point, the pH could still be low from two days prior when I added the half gallon of acid, but not always.
If the pH was high again, I would then add more acid when I shocked the pool the second time. If the pH was low, then I wouldn’t add any more acid as it didn’t need it.
Eventually, the pool would clear up and the pH would go to a normal range (7.2-7.8). If the green pool customer became a long-term maintenance customer after that (which happened often), then I may never have had to adjust the pH ever again as long as I kept the pool water nice.
Conversely, chlorine stays in the water longer and works better at maintaining clear water with a slightly higher pH. So, if a pool was nice and clear but didn’t like keeping a chlorine reading between weekly visits, then I might raise the pH in the pool to help keep the chlorine residual last longer. NOTE: This is independent of stabilizer/cyanuric acid levels.
Now, since this article is for you the single pool care person, then you should only be concerned with what your pH is in relation to chlorine if your pool turns green. Otherwise, keep it simple by not worrying about it.
THE RELATIONSHIP BETWEEN ALKALINITY AND PH
A pool’s alkalinity or total alkalinity can really mess with a pool owner’s head. For most, it’s just a thing on a test strip or something to test for in a kit with a normal range to try to achieve.
As stated earlier, “this is chemistry”. So if you want, you can go as deep down any rabbit hole as you feel like. And it will take you way down deep into a complete darkness of understanding.
What are you wanting to accomplish though? Are you looking to get a degree in chemistry OR take care of your swimming pool as easy as possible?
99 times out of 100, you won’t have to worry about total alkalinity in your swimming pool. And with that, this is all you need to know
The relationship between pH and TA has to do with the pH’s ability to fluctuate. That’s it!
As a professional pool maintenance person, I would never pay attention to (TA )or alkalinity. The only time I would test for its level was if the pH of the pool was fluctuating too much, which was not often.
Typically, the total alkalinity level of a pool will slightly adjust when you adjust the pH of the pool, but sometimes if it’s way out of whack, then it will need to be adjusted independently of the pH reading.
And this is how I adjusted TA only:
To lower the total alkalinity (TA) – I would introduce muriatic acid into the pool by walking around the pool and pouring a small constant amount (or trickling it) into the water.
This is a subtle difference from how I lowered pH in the pool, which was to pour the entire amount of muriatic acid in one area. Broadcasting the acid slowing around the pool will lower only the TA and only temporarily lower the pH.
To raise the total alkalinity (TA) – For this, I would add the proper amount of sodium bicarbonate
This is a slight difference from raising the pH only, which is to add soda ash instead of bicarb.
In reality, I almost stopped using soda ash to lower pH altogether and would use bicarb when I needed to lower pH only, which turns out to be not too often. I did that just because it would keep the TA in check a little (but I rarely paid much attention to it).
KNOWITALL ADVICE: Don’t keep trying to adjust the total alkalinity of your pool. Doing so will affect your pool’s pH, which can start a vicious circle of constantly adjusting both. Only pay attention to your total alkalinity if the pool’s pH is fluctuating greatly OR your pool water is cloudy and you don’t know why.
GO MORE BY THE LOOK AND FEEL OF YOUR POOL WATER, NOT YOUR CHEMICAL READINGS
One of the biggest mistakes pool owners make when maintaining their own pool is that they are more concerned with what the ranges are on their test kits/strips than what the pool water actually looks and feels like.
CERTAIN POOLS LIKE THEIR PH TO BE A CERTAIN LEVEL. DON’T FIGHT IT.
The recommended range for pH in a swimming pool is between 7.2 -7.8. Some won’t be happy unless their pool water is at 7.6, so they tinker with the levels constantly only to have the pool stay at something like 7.8-8.0. That’s fine.
Each body of water is different. When you maintain enough separate bodies of water during the same period, you learn that.
A swimming pool represents nature. Humans may have built the structure to hold the water, put the water in it, keep the area clean from fallen debris, control the temperature of the water, cover it from the elements, and add chemicals to continuously kill life trying to exist in it, BUT it’s still nature.
Humans can’t control nature! We may be able to maintain a range of it and may understand how a little of it works, But we don’t control it.
If you’re fighting to keep a certain pH in your pool, stop. Leave it alone and see what it wants to be on its own.
Ask yourself what the goal is here with taking care of your pool. Is it to have clean and healthy water that looks and feels great for the minimum amount of effort? Or is it to don a white smock, get out your beaker set, and spend extra money and time experimenting keeping an environment of nature perfectly sterile through the science of chemistry?
As a former pool maintenance company owner, people paid me to make and keep their swimming pool looking and feeling good. And to that end, a minimalist approach was needed. This is my advice to you.