Pool Alkalinity Calculator
Find out exactly how much baking soda or acid you need to balance your pool’s total alkalinity.
Enter your current Total Alkalinity reading and your target goal. The ideal range is usually between 80 and 120 ppm.
What is Total Alkalinity and Why Does It Matter?
If you have ever struggled to keep your pool’s pH balanced, your Total Alkalinity (TA) is likely the culprit. Total Alkalinity is arguably the most important foundational chemical level in your pool.
Think of alkalinity as the “bodyguard” for your pH. Alkalinity absorbs major acidic and basic fluctuations in the water so that your pH doesn’t swing wildly up and down (a problem known as “pH bounce”). When your alkalinity is balanced, your pH stays stable. When your alkalinity is out of whack, your pH will be nearly impossible to control.
What is the Ideal Alkalinity Range?
The ideal Total Alkalinity for most swimming pools is between 80 and 120 ppm (parts per million). However, the exact perfect number depends slightly on the type of sanitizer you use in your pool.
| Sanitizer Type | Ideal Alkalinity Range | Why? |
|---|---|---|
| Liquid Chlorine / Bleach | 80 – 100 ppm | Liquid chlorine naturally raises pH over time, so keeping TA on the lower end helps slow down that pH rise. |
| Saltwater Generators (SWG) | 80 – 100 ppm | Salt cells naturally create high pH environments. A lower TA buffer helps prevent the pH from climbing too fast. |
| Trichlor (Chlorine Tablets) | 100 – 120 ppm | Trichlor tabs are highly acidic. A higher TA buffer is needed to prevent the acidic tabs from crashing the pH. |
| Bromine | 100 – 120 ppm | Bromine is acidic, so a higher alkalinity buffer is recommended. |
How to Raise Pool Alkalinity (The Baking Soda Method)
If your alkalinity is below 80 ppm, you need to raise it. Low alkalinity causes “pH bounce,” corrosive water that can damage pool equipment and etch plaster walls, and skin and eye irritation for swimmers.
The best, safest, and most cost-effective way to raise Total Alkalinity is to use Sodium Bicarbonate. You might know it by its common household name: Baking Soda.
Many pool stores sell expensive buckets labeled “Alkalinity Increaser” or “Alkalinity Up.” If you look at the active ingredients on the back, you will see it is 100% Sodium Bicarbonate. It is exactly the same chemical as baking soda, just marked up in price.
How Much Baking Soda to Add:
The standard formula is: 1.5 lbs of baking soda will raise the alkalinity of 10,000 gallons of water by 10 ppm.
Step-by-Step Instructions:
- Use the Pool Alkalinity Calculator above to find your exact dose.
- Ensure your pool pump is running so the water is circulating.
- Broadcast the baking soda across the surface of the deep end of the pool.
- Use a pool brush to push around any powder that settles on the floor to help it dissolve.
- Leave the pump running for at least 6 hours, then retest your water.
How to Lower Pool Alkalinity (The Acid & Aeration Method)
If your alkalinity is above 120 ppm, you need to lower it. High alkalinity forces your pH to remain stubbornly high, which renders your chlorine ineffective, causes cloudy water, and creates calcium scaling on your pool walls.
Lowering alkalinity is trickier than raising it because the chemicals used to lower alkalinity also lower your pH significantly. You have two chemical options: Muriatic Acid (liquid) or Dry Acid (Sodium Bisulfate powder).
How Much Acid to Add:
- Muriatic Acid (31.45%): 25.6 fluid ounces lowers the alkalinity of 10,000 gallons by 10 ppm.
- Dry Acid (Sodium Bisulfate): 2.1 pounds lowers the alkalinity of 10,000 gallons by 10 ppm.
The “Acid & Aeration” Technique (Crucial!)
Because adding acid lowers both alkalinity and pH, you must bring the pH back up without raising the alkalinity again. The secret to raising pH without affecting alkalinity is aeration (introducing air into the water).
- Use the calculator above to find out how much acid to add.
- Add the acid to the deep end of the pool with the pump running. (Always add acid to water, never water to acid!)
- Wait 30 minutes, then test your pH. It will likely be very low (around 7.0 or 7.2).
- Aerate the water! Turn on all water features, fountains, waterfalls, or point your return jets up toward the surface so they break the water. This off-gasses carbon dioxide, which naturally raises the pH over a few days while keeping your alkalinity at the new, lower level.
Alkalinity vs. pH: Understanding the Relationship
It is very common for pool owners to confuse pH and Total Alkalinity because they are deeply connected. They move together, but they are not the same thing.
- pH measures how acidic or basic your water is. It determines how comfortable the water is to swim in and how effective your chlorine is.
- Total Alkalinity measures the amount of alkaline substances (carbonates and bicarbonates) in the water. Its sole purpose is to act as a buffer to protect the pH.
Think of it like this: pH is the temperature in your house, and Total Alkalinity is the insulation in your walls. If you don’t have good insulation (low alkalinity), a draft outside will wildly swing the temperature inside (pH bounce). If you have too much insulation (high alkalinity), it becomes impossible to cool the house down when it gets too hot.
Frequently Asked Questions
Can I use regular baking soda to raise alkalinity?
Yes! Arm & Hammer baking soda found in the grocery store is 100% sodium bicarbonate, which is the exact same chemical sold in pool stores as “Alkalinity Increaser.” Buying large bags of baking soda from warehouse clubs like Costco is often the cheapest way to manage pool alkalinity.
Does adding muriatic acid lower pH or alkalinity?
It lowers both. Muriatic acid is highly acidic, so it immediately drops your pH, and in the process of neutralizing the basic buffers in the water, it also lowers your Total Alkalinity. This is why you must use aeration to bring the pH back up afterward.
What happens if pool alkalinity is too low?
Low alkalinity causes “pH bounce,” meaning your pH will wildly fluctuate with every rainstorm or swimmer entering the pool. The water becomes acidic and corrosive, which can burn eyes, dissolve the copper in heat exchangers, and etch the plaster off the walls of the pool.
What happens if pool alkalinity is too high?
High alkalinity acts as an anchor that locks your pH at a high level. High pH makes your free chlorine sluggish and ineffective, which can lead to algae blooms. It also causes dissolved calcium to precipitate out of the water, creating cloudy water and rough white scales on the pool walls.
How long after adding baking soda can we swim?
Baking soda is a very safe, mild chemical. As long as you have brushed it around so there are no piles of powder on the bottom of the pool, you only need to wait about 20 to 30 minutes (or one full turnover cycle of your pool water) before it is safe to swim.
How long after adding muriatic acid can we swim?
Muriatic acid is a harsh, dangerous chemical in its concentrated form. You should wait at least 30 to 60 minutes with the pump running on high speed to ensure the acid is fully dispersed before allowing anyone to swim. You should also retest the pH to make sure it hasn’t dropped dangerously low (below 7.2).