Total Alkalinity is often a hidden or ignored problem to many pool owners. They just don’t know or don’t understand the water chemistry let alone know how to lower the alkalinity level in their pool.
Total alkalinity is a measure of the total concentration of alkaloids (carbonates and other alkaline compounds) dissolved in water. The correct level of Total Alkalinity serves to buffer pool water by resisting changes in the pH keeping the water chemistry balanced.
When the Alkalinity in a pool is too high acid or sodium bisulphate needs to be added to the water. Increase low Alkalinity in a pool with the addition of Sodium Bicarbonate (baking soda).
Table of Contents
What is Total Alkalinity in Pool Water
Alkalinity and pH are not the same thing but they correlate together.
pH is a scale in chemistry to indicate the level of acidity or alkalinity in a solution.
Swimming pool water should normally be between pH 7.2 and 7.8 which is slightly alkaline and never acidic.
Total Alkalinity in pool water is the measure of all alkaline compounds dissolved in the water. It is a measure of the water’s ability to resist changes in pH by providing capacity to neutralize acid. The right amount of alkalinity helps to buffer your pool water from changes in pH.
In the swimming pool industry, total alkalinity is a measure of the dissolved carbonates and bicarbonates in water in parts per million (ppm).
The Total Alkalinity in pool water should be between 80 – 120 ppm.
Vinyl Lined Pools should have a level 100 to 150 ppm
Fibreglass Pools should be 80 to 100 ppm
Concrete Pools with a pebble aggregate lining should be 100 to 200 ppm
Testing for Total Alkalinity in Pool Water
Whenever you normally test your pool water you should test for total alkalinity.
I highly recommend using pool water test strips because they are simple to use, accurate and most include a test for total alkalinity.
High Alkalinity Level in Pool Water
A high total alkalinity can occur when too much chemical, such as sodium bicarbonate or chlorine shock, has been added to the water too quickly. I always recommend to add small quantities of chemical, wait a while and retest the water before adding further amounts of chemical. Yes, it is a slower process but the only way to guarantee that too much chemical is not added resulting in unbalanced pool water.
High total alkalinity can be caused by the water supply to your pool.
If your pool water test is indicating total alkalinity is too high you will need to lower alkalinity in your pool water. Otherwise, you will encounter the following problems:
- High and unstable pH level.
- High calcium level and scaling
- Cloudy pool water
- Chlorine becomes less effective resulting in algae growth
- Filter frequently clogging up
- Irritated eyes and itchy skin for swimmers
Low Alkalinity Level in Pool Water
A low total alkalinity can occur after heavy rainfall especially acid rain.
A low total alkalinity in pool water may lead to the following issues:
- Stains forming on the pool surfaces
- Pitting, etching or erosion of the pool surfaces
- Irritated eyes and itchy skin for swimmers
- Green water
- Rapid changes in pH
- Corrosion of metal equipment parts (ladder, vacuum pole etc.)
Lower Total Alkalinity in Pool Water
Note: If you need to adjust both pH and Total Alkalinity, always adjust the Total Alkalinity level first as the pH may change.
If the pH level is already high, then the simplest way to reduce Total Alkalinity is to add small amounts of acid to the pool. This will be a slow process as you will need to test every day and add more acid until the Total Alkalinity and pH has been reduced to an acceptable level.
Add Hydrochloric acid to the Pool Water
Begin by adding one cup of hydrochloric acid or muriatic acid into the pool water.
Ensure you read the instructions on the container and practice safe handling of chemicals. Make sure you have spread the acid around in the pool and not poured it into one location as it may begin damaging the pool surfaces or tile grouting.
The best time to add the acid is just before the pool pump is due to come on. Otherwise, you will need to run the pool pump for several hours to mix in the acid. After mixing or the next day, test the pool water. If the Total Alkalinity and pH are both still too high repeat the above process until the levels are normal.
When either the pH or Total Alkalinity has reduced to the normal level stop the process. You may need to further adjust pH or Total Alkalinity separately with another process to correctly balance the water.
If the pH level is normal but Total Alkalinity is still too high use sodium bisulphate to lower the Total Alkalinity as this will not adversely change the pH. Please ensure you carefully follow the instructions on the container using the correct dosage for your volume of pool water. Again I recommend to lower the level in small increments with re-testing over several days to prevent adding to much chemical to the pool.
How to Increase Total Alkalinity in Pool Water
It is more common to encounter low Total Alkalinity than high Total Alkalinity, however both problems need to be corrected by rebalancing your pool water chemistry.
Sodium bicarbonate raises total alkalinity in pool water. This is simple process of adding the required quantity to the water. Simply follow the instructions on the container but be careful not to add too much chemical as you may raise the alkalinity too high. I recommend to raise the level in small increments and re-test over several days to prevent raising the level to high.
If you need to raise both Total Alkalinity and pH together use sodium carbonate (soda ash). However, sodium carbonate can cause cloudy pool water so only add small amounts at a time.
Lower Total Alkalinity in a Spa or Hot Tub
The methods of increasing or lowering alkalinity in spas and hot tubs is the same as with swimming pools. However, it is even more important to balance water chemistry in spa pools and hot tubs because they have a much smaller volume of water and the water is heated which can cause more rapid changes in water chemistry.
There are many branded products, in the marketplace, especially designed to increase or decrease the total concentration of alkaloids in hot tub water. The important point to remember is to only add small amounts of chemical to the water and retest the water after mixing with the pump.
How to Add Chemicals to a Swimming Pool
Pool chemicals are dangerous and reactive. Please store all pool chemicals in a cool, dry location and kept out of the reach of children. Wear gloves and protective clothing when handling chemicals.
Always read the label on the product and follow the instructions for adding the chemicals to pool water. Some products can be poured or spread directly into the pool. Other products recommend you add the chemical to a bucket of water first, mix it and spread around the pool. Make sure the bucket is clean and doesn’t contain any chemical residue as it may react with the product you are mixing in the bucket.
I recommend to run the pump for a few hours after adding chemicals to pool water to ensure the product is thoroughly mixed in. The best time to add chemicals is right before the pump is due to operate. So look at the timer and add chemicals when the pump comes on.
NEVER MIX CHEMICALS TOGETHER
Many people have suffered chemical burns, explosive reactions or breathed in toxic chlorine and burnt their lungs when mixing pool chemicals.
You should never mix pool chemicals together. They may react leading to fire, explosion or release of toxic chlorine gas. Even mixing dry chlorine with liquid chlorine may cause an explosion.
NEVER ADD WATER TO CHEMICALS, ALWAYS ADD CHEMICALS TO WATER
You must never add water to chemicals because the chemical may react with the water. It may cause an explosion or the release of toxic chlorine gas that has the potential to damage your lungs.
Always add a small amount of the chemical to a large amount of water to minimize any unwanted reaction. For example, mix the chemical into a clean full bucket of water or pour the chemical directly into the pool.
When to Add Chemicals to a Pool
The best time to add chemicals to a pool is when your family has finished using the pool for the day. So late afternoon or early evening is the ideal time because you cannot swim in a pool when you have just added chemicals. Also, the pump takes time to mix in the chemicals.
Adding the chemicals in the evening prevents UV sunlight from inactivating the chemicals. It ensures the chemicals have the longest amount of time to work before the UV light returns the next day. Adding chemicals, especially chlorine, in the middle of a hot summer day is least effective. It will evaporate quickly and become ineffective by UV radiation.
Ensure that your pump is going to operate for at least 3 or 4 hours after you have added the chemicals. This mixes and circulates the product thoroughly around the pool.
Conclusion
Total Alkalinity is often a complete mystery to many pool owners especially if they didn’t study their high school chemistry. However, it’s an important component in your pool water chemistry that cannot be overlooked. Unbalanced pool water can cause many unwanted side effects including damage to your pool surfaces. Following a basic pool maintenance and testing schedule will ensure alkalinity is never a problem and enhances the lifespan of your pool.