If your alkalinity level becomes too high, it will become difficult to change the pH. You'll know your pH is too high when your pool water is cloudy, there is scale build up on your pool walls and your chlorine is no longer successfully sanitizing your pool.
The two most popular chemicals available to help you lower the total alkalinity in your swimming pool are muriatic acid and sodium bisulfate (also known as dry acid).
High Alkalinity
High total alkalinity can make pool water appear cloudy and cause scale deposits to form on the sides of the pool, pool equipment and plumbing. Scale can be removed, but the process is difficult and the chemicals that remove it require several weeks to work.
As it turns out, alkalinity rises due to excess hydroxides left behind by hypochlorite chlorines: sodium hypochlorite (liquid chlorine) and calcium hypochlorite (cal hypo). There is a minor net rise in TA when all things are fully oxidized in the water.
The fastest, easiest way to reduce alkalinity is to dilute the aquarium water with purified, low-mineral water. Reverse-osmosis or RO units produce water with almost no dissolved minerals. You can add this water to the aquarium to water down the overly alkaline water.
Baking soda, also known as sodium bicarbonate is naturally alkaline, with a pH of 8. When you add baking soda to your pool water, you will raise both the pH and the alkalinity, improving stability and clarity. Many commercial pool products for raising alkalinity utilize baking soda as their main active ingredient.
Another cause for high alkalinity can be when you shock the pool. While this is performed to quickly rid the pool of pollutants, chlorine-based pool shock is highly alkaline, and can raise the water's total alkalinity level in the process.
Pool water with a high total alkalinity (TA) is often associated with cloudiness. This is because it can cause an imbalance in the pH levels and lead to calcium scaling. Typically if your TA is higher than 200 ppm, you're at risk of a cloudy pool and just like imbalanced pH levels, your chlorine will be less effective.
Can You Safely Swim in a Pool With High Alkalinity? As long as you have enough chlorine in your pool (around 3ppm for total chlorine) and the pH level is balanced (between 7.4 to 7.8), then a pool with high total alkalinity is still safe to swim in.
You can decrease pH without lowering the Total Alkalinity using Carbon Dioxide (CO₂) injection for pH control. Still, this does not lessen one without an effect on the other. When CO₂ is injected into water, it forms carbonic acid (H₂CO₃), which will reduce the pH.
Algae is certainly the cause of the green, but an imbalance of pH and/or alkalinity is why you have algae in the first place (while there is adequate chlorine). Very high or low pH significantly decreases the effectiveness of chlorine.
Alkalinity is the total alkaline material in your pool water. You should test alkalinity first because it will buffer pH. Your reading should be in the range of 80 to 120 parts per million (ppm).
Your patrons will notice, too, since high acidity (low pH) will irritate or even damage eyes, skin, and mucous membranes (such as the inside of your nose). Low pH also tends to lower total alkalinity. High pH is also a problem for your pool. When the pH is too high, your water is very basic.
Using liquid chlorine raises the pH of the water.
Liquid chlorine does not raise pH. When added to water, liquid chlorine (which has a pH of 13) makes HOCl (hypochlorous acid – the killing form of chlorine) and NaOH (sodium hydroxide), which raises pH.
Fortunately, high alkalinity is 100% curable so long as you know what to look for. If you're in a hurry, the short and sweet answer to lower the alkalinity in your swimming pool is by adding either muriatic acid or sodium bisulfate.
What Happens if Alkalinity is Too High in Hot Tub? The main thing that can happen is it renders your sanitizer (chlorine, bromine, etc.) useless. And that can cause your water to turn green and bacteria to grow making the hot tub unsafe to soak in.
Now it's important to note that high alkalinity levels will naturally decrease over time on their own. But high total alkalinity can precipitate other issues, like high pH and ineffective chlorine, which can lead to algae. So it's often worth addressing high alkalinity levels before they can cause more trouble.
To lower the alkalinity in your pool, try using a strong acid like muriatic acid, sodium bisulfate, or sulfuric acid all of which will lower the alkalinity. If your pool water is a little murky or your pool filters seem to be plugged with calcium deposits, then your pool may be suffering from high alkalinity levels.
When water is too alkaline (pH is high), it can impact the balance of other chemicals in the water. While alkaline water alone doesn't tend to trigger algae growth, it's an indication that the pool is off-balance—and that opens the door for algae.
Causes of Rising Alkalinity
It's also not uncommon for pool owners to go a bit overboard when shocking their pool, and since chlorine-based pool shock is a high-alkaline substance, it will also naturally raise your pool alkalinity.
Algae will remain in your pool after shock if you've had insufficient chlorine and an overabundance of metal elements in the pool water. Therefore, to start the cleaning process. Remove all the debris from the pool with a leaf net and then let the smaller dirt fragments settle.