Most people that have a pool in their backyard probably know that the pH levels in swimming pools need to be maintained for safety reasons. But if the pH drops how do you raise it?
To raise the pH level in a pool, you can use either baking soda (sodium bicarbonate) or soda ash (sodium carbonate). You should add these in stages until the pH is between 7.2 and 7.6. Adding too much, too quickly, can have some adverse effects on your pool.
When a pool is not properly maintained, the pH level can drop to dangerous levels, both for the pool itself and the swimmers. It is therefore important to know how to quickly and safely raise the pH in a swimming pool.
Steps to take to raise the pH level
It is not a complicated procedure to raise the pH. Just remember to not try and raise it too much in one go, otherwise that could lead to other problems.
1. Test the water
The pH level is a measurement of acidity, and it is measured on a scale from 0-14, with lower numbers being more acidic and higher numbers being less acidic or alkaline. Test the water using test strips or liquid to determine how far off the ideal reading of 7.2 and 7.6 your pool water is.
You can also take a water sample to your local pool store to be analyzed and many will do this free of charge. Just be mindful that their main motivation for providing this service is to sell you chemicals.
2. Work out the amount of chemicals you need
To work this out you will need to know the approximate volume of water in your pool. You can read this post to find out how to calculate the volume of water.
If the volume is 10,000 gallons, and you need to raise the pH by 0.4, then you will need to add around 12 oz of soda ash or 3-4 lbs of baking soda.
I suggest that you always add in stages – add some, wait a few hours and retest. Add more if necessary.
3. Mix the chemicals with water
Whether you are using baking soda or soda ash, always fill a bucket with water and then add them to it, mixing thoroughly before adding to the pool. Don’t try and add too much at a time. Just enough to fully dissolve it, then do it again if you need to.
Never put the chemicals in the bucket first and put water in afterwards. Always water first.
4. Add mixed chemicals to the pool
Walk around the pool’s edge, pouring the chemicals from the bucket as you go to distribute them as thoroughly as possible.
5. Retest the water
Wait a few hours for the chemicals to thoroughly mix and do their job. If the levels are still low then carry out the procedure again.
What is the difference between baking soda and soda ash?
There is a big difference between the two. Baking soda is sodium bicarbonate (NaHCO3) and this has a pH of 8.4. Soda ash is sodium carbonate (Na2CO3) and this has a pH of 11.6, so it is far more alkaline than sodium bicarbonate.
It takes more baking soda to raise the pH by the same amount as it does soda ash which is more alkaline. Because of this it is easy to add too much soda ash and raise the pH more than is desirable. If you do this you will have to add something such as muriatic acid to bring the levels back down again. In other words, it is easy to end up chasing your tail, turning your pool into a chemical bath.
Baking soda is likely to increase the total alkalinity in addition to raising the pH whereas soda ash will have less of an affect on total alkalinity. So if your total alkalinity is close to being correct but your pH is low then use soda ash.
What causes low pH in the pool?
If the pH is too low, it could be due to a variety of factors including natural decomposition of organic matter and high levels of metals in the water. In pools without chlorination systems, lowering the pH will also cause higher chlorine demand, leading to increased chemical costs for maintenance.
Low pH in the pool can be caused by either high chlorine levels or low alkalinity.
High chlorine levels
A high chlorine level in the pool means that there is a higher concentration of hypochlorous acid than would be expected. Hypochlorous acid kills bacteria and other germs, but it also causes low pH levels.
The cause for this could either be too much chlorine being added to the water or not enough time before adding more chlorine.
Low alkalinity in the pool is caused by an imbalance between pH and calcium hardness. When there isn’t enough calcium present, many of the bicarbonates will convert to carbon dioxide instead. The result is that too much water is being absorbed into the plaster causing a buildup on the bottom, which lowers pH levels.
Pool Maintenance Course
When I first bought my house with a pool I knew nothing about how to clean and maintain it. I was recommended Swim University’s Pool Care Handbook so I bought it and have never regretted it. It was probably the best money I spent that year as I have saved thousands by doing it myself.
What happens if pH is too low in the pool?
The pool’s overall health could suffer if proper care isn’t taken because bacterial growth rates increase with lowered pH. It may not take long before you have a green or black slimy surface as well as an unpleasant odor coming from your pool.
It also can affect swimmers’ experience like itchy eyes and irritated skin. The pool pH should be in the range 7.2 to 7.6 which is generally a similar pH to that of human tears. If the pH is lower than this (or higher) then that is a major factor in making eyes sore after opening your eyes under water. When that happens people assume it is because of too much chlorine but that isn’t usually correct. It is more likely incorrect pH.
Does low pH affect chlorine?
Low pH has a huge impact on chlorine. Chlorine needs a pH of at least 7 to work properly, so if the pH in a pool is below this level, it will have severely reduced effectiveness.
This means that even though you may be adding enough chlorine for effective cleaning and disinfection purposes, low pH levels can increase bacteria counts dramatically – which could lead to skin irritation or eye damage.
To avoid these drawbacks, keep your water at an acceptable pH range by monitoring regularly with a test kit and adjusting accordingly when necessary.
Does low pH in the pool cause algae?
The answer to this is “yes and no”. Low pH doesn’t cause algae; but, the high levels of chlorine in combination with low-pH in a pool can promote algal growth. Basically, low pH in your pool will not affect directly the algae in your pool, but it can help the algae grow faster.
Algae in a pool can be caused by several different factors. Algae needs a balance between chlorine and pH-determining chemicals to thrive in water – when any of these are out of the desired range, algae will form.
This happened to me this spring actually when I opened my pool (not that I actually close it as the climate is very mild here). I had neglected the pool for a few weeks as I had to go overseas and when I checked the pool chemistry the pH was very low. So I added a quantity of pH Plus (alkaline). Within a few hours the pool went from clear to green, as you can see in the photo below.
I soon rectified this by shocking the pool a few times and then vacuuming on waste to remove the dead algae.
How long does it take to raise pH in the pool?
The goal of raising the pH in a pool is to restore it to acceptable levels for swimming, and this time will depend on how low the pH has been allowed to drop before being corrected.
To raise the pH in the average-sized pool, will take anywhere around 6 hours to 10 hours. But it’s important to remember, the more acidic the pool water is, the longer it will take for pH to balance.
If the pH has been allowed to drop below a level of around six, it could take up to 24 hours before reaching an acceptable level.
The time needed for pH balancing will be different depending on how low it’s dropped and what type of chemicals are being used.
Will shocking a pool raise the pH in the pool?
Shocking a pool with chlorine to raise the pH in a swimming pool isn’t going to raise the pH. The high levels of chlorine actually cause a lower pH level and can make it even worse.
To increase the pH, you need either sodium carbonate (soda ash) or sodium bicarbonate (baking soda) which is available at most home improvement stores. Pool stores will sell “pH Plus” but these are normally just sodium bicarbonate at higher prices.
These chemicals have a double effect: they work as chemical stabilizers (keeping pools clear) while lowering the acidity index (raising the pH).
So to summarize, the pH level in a pool is important because it affects the chemical balance of your water. When you maintain and monitor this ratio, you can prevent algae growth which will also help keep your entire swimming experience better for everyone involved.
If you have the opposite problem to low pH then you will find help here – What happens if your pH is too high