Hot tubs in particular generate a lot of bubbles and tend to have higher temperatures. This combination creates a gas called carbon dioxide very quickly. Carbon dioxide builds up and makes the pH go up. This is why hot tub owners, on a regular basis, need to add something to lower their pH and alkalinity.
In order to lower both the pH and alkalinity of your hot tub water, you will need to add acid. Common choices are liquid muriatic acid or dry sodium bisulfate. When the acid is introduced to the water, it increases the hydrogen concentration and lowers the pH.
Having pH levels that are higher than 7.8 or lower than 7.2 can cause problems for your and you hot tub. High pH is a common cause of calcium and scale build up at your hot tub water line and cloudy or dull water. It also causes bathers to often experience itchy skin and burning eyes.
Hot tubs are often at a pH level of 7.2 – 7.8. Adding chlorine will increase this number slightly, but because the chemical also reacts to form hypochlorous acid, which reduces acids and makes your hot water less acidic, there's no change unless large amounts of chlorine are added.
Natural contaminants on your body will lower the pH and make it harder for the chlorine to work. Adding too much shock, especially if the pH is already low, will make it harder to get your water in the proper range. When you add chemicals to your hot tub water, the goal is to keep it clean and clear.
To bring down pH, use a made-for-pools chemical additive called pH reducer (or pH minus). The main active ingredients in pH reducers are either muriatic acid or sodium bisulfate (also called dry acid). Reducers are readily available at pool supply stores, home improvement centers and online.
After adding pH increaser or decreaser you'll want to wait about two to four hours, although some chemical manufacturers suggest a full turnover cycle, before retesting. The smaller the increments you need to adjust for pH, the less time you'll need to wait for the results to become stable.
There are two main chemicals typically used to decrease pH in hot tubs, muriatic acid and dry acid (also known as sodium bisulfate). Although they are designed to do the same thing, pay attention to which chemical you are using, because how you add the chemical differs.
A pH level of 7 means that water is neutral; above 7 means the water is alkaline, while below 7 indicates acidity. Aim for a pH level of between 7 and 7.6. If the water pH is higher than 8, anyone who swims in the pool is at risk of skin rashes, while a pH of lower than 7 can sting swimmers' eyes.
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.
If you wish to lower the pH without also reducing the Total Alkalinity, simply pour the dose of muriatic acid about the pool. “ This would all be wonderful if it was only accurate. Still, just like the mythological “Chlorine Lock,” folkloric tales within the swimming pool industry do persist.
The most common reason for a consistently high pH level in pools is the use of liquid chlorine or a saltwater system as the primary sanitizer. Sodium hydroxide is produced, which has a pH of around 13. New pool plaster or pebble finishes will also raise pH in pools for about a year after installation.
High chlorine levels decrease the pH of your pool's water, making it more acidic. The more acidic the water, the higher the likelihood of corrosion. This corrosion can affect metal piping, equipment, and the surface of your pool (tiles, liners, concrete, etc.).
When you shock a pool, you test and adjust the pH level for a reason. With that said, if you shock a pool outside of the 7.2 to 7.4 pH range, not only will you waste a significant amount of the chlorine used, you will also end up with cloudy water.
When you've determined that your pool pH is too high, there are two ways you can balance it: dry acid or muriatic acid. If you're using a dry acid, use these steps: Follow the manufacturer's instructions on the package. Use the recommended amount only.
Ordinary household vinegar could in theory be used to lower the pH of your pool. The pH of vinegar is about 2.5, which is quite acidic when compared to your pool water. Household vinegar is very weak though (when compared to a strong acid like muriatic acid), so you would need quite a bit to lower pH.
There are a couple of ways you can lower pH in water. If you're drinking a glass of water, add a few drops of lemon juice. The acidity will lower the pH naturally. You could also install an acid injection system to your water supply to lower the pH of your drinking water.
Swimming pool pH reducer is made of granular sodium bisulfate and will act quickly to correct your pool's pH level to re-establish an ideal swimming environment. pH reducer can be used to lower swimming pool pH levels whenever they rise above 7.6 ppm.
Dilute 1 part acid into 10 parts of water (never the other way around). Mix up the solution in a large bucket using a wooden stir stick. Carefully pour the solution into the tub and let it circulate for a few hours. Retest the water and adjust the pH level if necessary.
If your chlorine levels are higher than 3 ppm and you don't need to use the hot tub any time soon, you don't have to do anything to reduce your levels. Just don't use the hot tub for a day or so and refrain from adding any more chlorine. Eventually, the chlorine will drop to safe levels on its own.
pH Decreaser gradually lowers your pH and alkalinity until at the desired level, and also prevents scale build-up and cloudy water that also usually occurs when your spa operates at the high-end of the pH scale.