Measuring pH (potential of hydrogen) is an important aspect of salt water pool water chemistry. For any pool, pH is something that needs to be monitored but since pH tends to drift higher in a salt water pool due to the salt chlorinator, it’s extra important.
a pH control unit is an add on to your salt water chlorinator that uses CO2 instead of a caustic product like muriatic acid to keep pH in check automatically. A system typically costs $800 – $1300 so the average pool owner may find it more economical to stick with adding acid when required.
While pH does tend to go higher in a salt water pool than other pool types, it’s usually manageable. The cost of a pH control unit may be prohibitive for many pool owners especially since it’s similar to the price of an entire salt chlorination system.
Below we’ll ask if a pH control system is worth it, what other pH control options are available and just what is pH to begin with? We’ll answer each question too, of course!
What does a pH control unit consist of?
A pH control unit is a CO2 injection system that is typically comprised of a pressure reducing regulator, solenoid valve, tubing and PVC check valve injector. A standard CO2 tank is also required (purchased separately) as the product uses CO2 in place of an acid such as muriatic (hydrochloric) acid.
You can choose a CO2 container size that fits your pool water volume but the manufacturers often suggest a size of 20 lbs. will suit most average salt water pool owners. The bigger the tank, the less you’ll have to refill it. When you refill it, it’s similar to refilling a propane tank for your BBQ.
Most pH control unit products can be self-installed and simple to operate as long as you follow the instructions. They’re not cheap however and only serve to manage pH.
A pH control unit will help to control pH only and will not help you lower alkalinity. Alkalinity measures your pool water’s ability to resist a sudden change to pH. A high alkalinity will help to increase pH though.
So the pH control system does one thing and one thing only: It controls pH.
Why is high pH a problem with salt water pools?
pH tends to drift higher in salt water pools because the salt chlorinator produces chlorine and a byproduct of salt water chlorination production is Sodium Hydroxide which has a very high pH of 14. A salt water pool’s ideal pH is 7.6 with the acceptable range being 7.2 – 7.8.
You want to keep your chlorine level between 1 ppm and 3 ppm unless your local pool company tells you otherwise. The more you run your salt cell, the higher the pH over time because you’re producing Sodium Hydroxide along with the chlorine.
So if you’re running your salt cell too much, you might want to dial it down a bit to help lower pH as long as your chlorine level doesn’t suffer. If you find that your chlorine is running on the high side, you can either run your pump less and/or turn the chlorinator setting down slightly to see if that helps to lower pH over time without leading to you accidentally producing too little chlorine.
Keeping your stabilizer (cyanuric acid) level in check is also important to managing pH. Keeping your stabilizer between 80 ppm and 100 ppm will help to protect your chlorine from the harmful rays of the sun which kills chlorine. Protecting free chlorine will lower your need to produce more chlorine. This in turn can help to keep your pH in line!
While regular pool owners are often told to keep stabilizer at 50 ppm – 80 ppm, salt water pool owners are usually requested to have a higher cyanuric acid level in their pool to help better protect the chlorine and also keep pH down.
Will pool pH go down on its own?
A salt water pool’s pH can over time decrease on its own but if it’s too high, it should be dealt with proactively. If the pH is slowly drifting higher and is already too high, it’s possible it’s going to continue trending upwards unless you do something about it.
It’s kind of a self-fulfilling prophecy once the pH exceeds 7.8, too: The higher the pH, the less effective your chlorine and the more chlorine you might need to produce which in turn helps to increase the pH even more.
Adding stabilizer if needed or reducing the pump or chlorinator time can help. As mentioned above, you might need to use muriatic acid to reduce the pH too.
Many salt water pool owners do find that they have to deal with high pH especially during periods of high chlorine production – heavy pool usage and hot sunny days. But in my experience, dealing with high pH is at best a once or twice per season problem that requires attention.
Is it worth spending $800 + on an automatic pH control unit? Hard to say but for the average salt water pool owner, probably not.
Can I swim in pool with high pH?
You can swim in a pool that has a slightly high pH but at some point, the level can become too high. A pH higher than 8 is a risk for skin rashes and swimmers may also notice a number of other side effects including itchy skin and burning eyes.
You will also notice the pool water starting to get cloudy and pool equipment can experience scaling.
Having said that, we’ve owned a salt water pool since 2006 and having seen the pH drift high enough once per season every year or second year from memory, and being advised by our pool company to lower it with acid on several occasions, I can also say that we have never had a complaint or problem with any of the above-mentioned aspects of high pH.
No one swimming in our pool has experienced itchy skin, reddened eyes or any other associated problems. We have no problems with scaling on our pool equipment either.
So keep your pH in check but if you’re following the instructions of your chlorinator and keeping the other aspects of water chemistry in line, chances are your pH will be just fine on its own.
Summary
Spending $800 or more plus paying for CO2 replacement every season or so seems like a lot of money to spend on a piece of equipment that only does one thing, namely keep pH in check.
In my experience as a salt water pool owner, pH tends to remain in check and when it does drift a bit high, the occasional use of some acid to bring it back tends to do the trick just fine.
