Your pool water test has just indicated the pH is way below 7.2 and you need to increase it back into the normal range of 7.2 to 7.8. How to raise the pH level in pool water is one of the most common issues encountered by pool owners so let’s find out how to fix it.
Your swimming pool water is now more acidic than normal so it needs adjustment to be more alkaline by raising the pH. Adding sodium carbonate (soda ash) or sodium bicarbonate (baking soda) will increase pH but you need to be careful with total alkalinity when adjusting pH.
Table of Contents
What is pH?
pH is a scale in chemistry to indicate the level of acidity or alkalinity of an aqueous (water-based) solution. The symbol pH means “power or potential of hydrogen”.
Strong acid is pH 0
Strong base (or alkaline) is pH 14.
Pure water, at 25C, is neutral at pH 7.0.
pH can fluctuate on temperature, for example, pure water at 0C is pH 7.4.
Sea water is normally between pH 7.5 and 8.4.
Swimming pool water must be between pH 7.2 and 7.6 which is slightly alkaline and never acidic.
Pool water must be at the correct pH to ensure the effective operation of your salt water chlorinator to produce adequate chlorine levels to kill algae and bacteria. The correct pH protects the pool surfaces and metal finishes from deterioration.
If you don’t have a salt water pool chlorine must be administered by a floating chlorine dispenser or manually added to the pool every day.
We also have information on How to Lower pH in a Swimming Pool
What Causes Low pH?
The pH level of your pool water can be influenced by many environmental factors including:
Pool chemicals: Shocking your pool or adding other agents can change the acidity of the water.
Swimming: When people swim in the pool they leave chemical residues such as sunscreen lotion, makeup, body lotions, shampoo, hair gel, deodorant, saliva, urine (unfortunately it happens) and anything they use on their body. All of these products can affect the pH.
Rainwater: Most rain across the world is slightly acidic which will lower the pH of pool water. The best way to prevent this is with a pool cover.
Organic matter: Leaves, grass and insects floating in the pool can influence pH.
Local Water Supply: What was the water supply used to fill or top-up the pool? Tap water is usually slightly alkaline. Tank water can be acidic if collected from the roof. Water from bores, dams or rivers can have varying pH levels.
What happens if pH is too Low in Pool?
Acidic water is mildly corrosive and over time can damage metal fittings, plastic, grout and the pool surfaces. This includes your filtration system, pipes, valves, ladders, railings and pool cleaning equipment.
If your pool is lined with marble plaster (such as marble-lite, marble-sheen products) you may get etching and pitting into the plaster that leads to black spots that are very difficult to remove. The plaster releases minerals into the water upsetting the water balance causing more problems.
Pools lined with fibreglass or vinyl-lined are not safe either. A low pH will eventually cause vinyl and plastic to become brittle, crack and tear. My father’s pool was fibreglass lined over concrete and old plaster. The fibreglass eventually become brittle and cracked allowing water to run behind the fibreglass lifting it from the concrete. When we emptied the pool I was able to tear large sheets of fibreglass off the sides and the fibreglass coating over the shallow end was floating on the concrete.
However, the main issue with low pH is that it will render chlorine ineffective against sanitizing your pool water. The chemical properties of chlorine only work in water with a fairly neutral pH. Adding extra chlorine or even shocking the pool won’t solve the problem. This will leave your pool exposed to algae and bacteria making the pool unsafe for swimming.
Is it Safe to Swim in a Pool with a Low pH?
Don’t swim in water with a low pH. The mildly acidic water may sting your eyes, irritate your skin and annoy you nasal cavity. Your skin could be left feeling dried out and itchy the next day. Children’s skin is more sensitive than an adult and will be more severely affected by low pH water.
Also the water is more prone to the growth of algae and bacteria which raises real health concerns for the safety of your family. Do you really want to risk the health of your family with acidic pool water and the possibility of bacterial infections?
How Do I Fix Low pH in My Pool?
The most widely used substance to raise the pH level in pool water is sodium carbonate which is commonly called soda ash. There are many branded products with names such as “pH Increaser”, “pH Raiser”, etc. which all contain basically the same ingredients (sodium carbonate or sodium bicarbonate) in varying concentrations. Any of these will do the job.
Just make sure you follow the instructions on the container and don’t add too much on the first application. If you add too much chemical you will increase the pH too high and need to purchase another chemical to reduce the pH. Add the chemical to the water above the outlet jets to ensure it’s well mixed into the water and leave the pump running for at least an hour.
A common problem for pool owners, especially if they have just bought the house, is they don’t know the volume of their pool. To determine the correct amount of chemical to add to the pool you will need to know the volume of the pool in gallons or liters. This is simple to calculate if your pool is round or rectangular. However, if your pool is kidney, peanut, trapezoid, or some other custom shape and the pool varies in depth you will need to find out from the pool builder.
How to Raise the pH Level in a Pool
When adjusting pH the important thing to test is total alkalinity. When you adjust pH you will always affect the alkalinity of the water. Normally, when you increase pH you will also increase total alkalinity as the two chemical factors are co-dependent on each other. Once total alkalinity is at the correct level the pH will be more stable.
What happens if Alkalinity is high and pH is low?
In this case you always need to adjust the total alkalinity first and pH second. Use a chemical to lower the alkalinity and wait a day for the water to recirculate and mix. Test again and if the alkalinity is ok, add a pH increaser to raise the pH slowly to the correct level. It‘s important to only increase the pH in small increments, allow the pool water to recirculate and keeping testing.
Please read our article on How to Lower the Alkalinity in a Pool
How long does it take to raise pH in pool water?
It may take several days to raise the pH level in pool water to the correct the pH level. I recommend to use a smaller portion of pH increaser chemical at first and test again the next day. You can always add more chemical again the next day. If you add too much you create another problem where the pH is too high.
Ideal pH Level in a Pool
Swimming pool professionals recommend a pH between 7.2 and 7.6 which is just slightly more alkaline than pure water. This pH ensures that the chlorine in the water will have maximum effectiveness against bacteria and algae.
Does Rainwater Raise the pH in a Pool?
Mostly light to medium rainfall does very little to affect an average swimming pool. The volume of rain is small in comparison to the total volume of the water in the pool.
However, over time with frequent rain or a large storm the pool water pH may drop out of the accepted range for pool water. Heavy rain may cause and increase or decrease in pH.
If you maintain your normal pool testing and maintenance routine you will detect any change to the balance of your pool water. Then you can take action to correct it.
Can You Use Rainwater to Fill a Swimming Pool?
A Swimming pool can be successfully filled or partially filled with rainwater that was harvested in a roof water tank. I have successfully filled pools with rainwater. However, the water may be lower than pH 7.2 because rain is slightly acidic. Be ready to add a chemical such as sodium carbonate to the water to increase the pH to the correct range of 7.2 to 7.6.
Does Chlorine Raise the pH in Pool Water?
The normal amount of chlorine added to a pool manually or generated by a salt water chlorinator will not raise the pH level in pool water.
When all the other chemical indicators are in the normal range your pool’s health will be perfect for your family’s enjoyment.
Conclusion
Maintaining your pool water chemistry is a top priority for all pool owners. Then you will have clean and safe water for you family and friends.
Once you have your water chemistry balanced the pool will stay sparking clear and clean with little effort on your part.
