Last Updated: June 29, 2022

Ultimate Guide to Using Borax (Boron) in Your Pool

Written By: Pool Care Guide

Borates are ionic compounds that have been used for years in pools. Borax (Borates) is most commonly used in pools to control pH levels. helps guard against the formation of calcium carbonate, which can cause cloudy water and scale build-up on pool surfaces.

The compound also works as a solid source of borate ions that help prevent algae growth by inhibiting certain coenzymes involved with its life cycle.

What Is Borax?

  • Boron: An element from the periodic table
  • Borate: A salt formed from boron and oxygen
  • Boric Acid: An acid formed from boron, 3 oxygen, and 3 hydrogens
  • Borax: A salt of boric acid

Borax is a white chalky powder that has been used as an antifungal agent for thousands of years. It was reintroduced to the public in the late 1800s as a way to clean up mining residue. In the present day, with a tiny bit of research, you could easily find uses for it all over your house. In this article, we are going to discuss some of those uses as they apply to a pool.

How to Test Borate Levels?

Before we can add the right dose of borate, we need to know how much is already in the pool. The easiest way to check out these levels is by using a water testing kit either from your nearby hardware store or from Amazon if you want it delivered. 

How Much Borax (Boron) Should You Add to Your Pool?

Whatever your borate levels are right now, increase or decrease those levels to bring them into the range of 30 to 50 PPM. If you need to increase your borate levels, you can use the chart below to determine the needed dose of borax or boric acid. If you need to decrease the borate levels, you will need to drain a portion of your pool’s water.

Borate Dosages to Raise by 10 PPM

 10,000 Gallons20,000 Gallons30,000 Gallons40,000 Gallons
Borax Dose7.4 lbs
14.7 lbs22.1 lbs29.4 lbs
Boric Acid Dose4.8 lbs9.6 lbs14.3 lbs19.1 lbs

Borate Dosages to Raise by 50 PPM

 10,000 Gallons20,000 Gallons30,000 Gallons40,000 Gallons
Borax Dose36.9 lbs73.6 lbs110.4 lbs257.6 lbs
Boric Acid Dose23.9 lbs47.8 lbs71.6 lbs119.3 lbs

When adding Boraxor borates, keep in mind that they also increase pH (Reduces the acid). If adding borax raises your pH value too much, you will need to counter it with an acid. Most likely, that will be muriatic acid.

Borate Benefits

There are several notable benefits that borates provide. Some of them are improvements in the aesthetics and physical sensations of the water; clearer, shinier, and softer. Most of these benefits are tied to improvements in the water's chemical balance.

  • Algae preventative - disables photosynthesis and metabolism
  • Increases alkalinity
  • Improves oxidizer effectiveness and lifespan
  • Kills bees and prevents them from bringing the hive
  • Reduces how much chlorine you need
  • Relieves eye irritation...How?
  • Softens water and reduces scaling

Can Prevent Bees from Invading Your Pool

Like all known living creatures, bees need water. The boron will start to kill them when they find the water and interact with it. This can prevent them from returning to the hive and telling the rest of the bees that your pool will be a good source of water.

Borate works great for preventing bees from making a habit of sourcing water from your pool. If borate is added before Spring, it can potentially prevent bees from buzzing around your pool in the Spring and Summer. 

Water Hardness (Softer Water)

Water hardness refers to the concentration of dissolved calcium and magnesium in hard water.

These minerals come from sources such as limestone found in rocks, seashells, corals and animal waste that is eventually washed into rivers or lakes. At that point, they become part of the water supply. The Calcium in the water is beneficial in many ways. Every vertebrate requires calcium to build strong bones and teeth. 

It only becomes problematic in high concentrations in certain environments. High concentrations of calcium can be problematic for your pipes, appliances, and of course, your pool. In these environments, the calcium can build up as scaling along the pool walls and especially hot spots in the heater and pump.

How Does Borate Help Fight Calcium Scaling?

Boron has a strong negative charge of -3. When you add it to your pool water, the positively charged metals, magnesium (+2) and calcium (+2), are attracted to its negatively charged structure. When brought together, the calcium is no longer available to attach to your pool walls. The calcium 

Borates also help fight calcium scaling by increasing alkalinity. Increasing alkalinity helps to stabilize pH. We need to keep pH within a specific range, present acid will be powerful enough to dissolve any calcium that tries to attach to the wall. High alkalinity will also keep pH from dropping. If pH goes too low, the increased acidity will break down the pool floor and walls.

Unfortunately, it isn’t all good. While borates stabilize the pH they also raise the pH a bit. That is why muriatic acid often needs to be added in addition to the borates. The acid will counter the rising pH while the borates will stabilize it.

Clearer Water (Algae Prevention & Increases Alkalinity)

If water is clear, that is because contaminants aren't floating around. Borate helps to maintain this clarity in two major ways: algae prevention and raising alkalinity.

Algae Prevention

Borax (Borates) shouldn't be your first choice to kill algae already present in your pool. Instead, they are best used to prevent algae from forming in the first place.

The borates that make up much of the borax are molecularly compatible with algae's nucleotide coenzymes (NAD+ and NADP+) that are vital to photosynthesis and metabolization. When the borates pair with these coenzymes, the coenzymes are no longer free to perform their functions within the algae. To state it another way, borates starve algae of the food it needs to proliferate and survive.


We touched on this a moment ago, but we want to go into a bit more detail in its own section.

pH is a measure of a compound’s acidity. To put it another way, pH is short for “potential hydrogen.” The potential hydrogen refers to the ratio of hydrogen donators within a solution.  When there are lots of hydrogen donators, it is considered acidic. When a solution is considered alkaline, there are not many hydrogen donators.

Alkalinity is different from an alkaline substance. Alkalinity, sometimes referred to as ALK, is a measure of the water's ability to maintain a stable pH level. When you add a substance to increase alkalinity, you are adding what are known as buffering solutions.

Buffering solutions help maintain pH levels by switching back and forth between donating and accepting hydrogens. Buffering solutions pull off this magic act by chemically rearranging between a weak acid and a strong base or between a strong acid and a weak base. 

  • Acid: Hydrogen donators (AKA Proton Donators)
  • Base: Hydrogen acceptors

Acids donate hydrogens and bases accept them. The buffering solution will naturally become acid or a base depending upon chemical pressures: pH, temperature, and ratios of other substances within the solvent.

Buffering solutions can switch like this over and over.

Helps Control Corrosion

Borax is bivalent, which means that it has two atoms of boron attached to four oxygen atoms. As the water in your pool circulates past this compound, the algal cells that cause water to be cloudy are attracted to it because they have a positive charge that matches the negative charge on borax's ionic structure. 

The algae get trapped by exchanging their electrons with the boron center - often referred to as electron "sucking." This binding allows you to use less chlorine or other chemicals for cleaning and maintenance.

Baking Soda vs Borax vs Soda Ash

Baking soda, borax, and soda ash are chemically different, but they address some of the same issues. They are both alkaline compounds with high pH values. Their pH values are higher than the ideal pool pH of 7.2 to 7.4. Rainwater and tap water pH values are often too low. When pool water pH is too low, we can use these products to rectify the low pH.

  • Baking Soda: 8
  • Borax: 9.5
  • Soda Ash: 11.3 to 11.8

pH is measured on a logarithmic scale. Each number on the scale has 10x the value or 1/10th of the value of the one next to it.

If we consider the logarithmic scale, that means baking soda's pH of 8 is 1,500% more acidic than borax. It also makes borax a great way to reduce acid.

pH is rated on a logarithmic scale. A pH value of 5 is 10x more acidic than 6 and 1/10th the acidity of 4.

Questions and Answers

How Long After Adding Borax to a Pool Can You Swim?

With the pool pump running, it should only take about 30 minutes to disperse. After that, you can hop into the pool and start swimming.

How Long Does Boron Last?

Borate products such as borax should last you about a year. Borate doesn't evaporate. It will only leave the pool by splashing out or being drained. It will remain useful until a change in the pH has overwhelmed its ability to buffer against the pH change, or until the borates have bound to molecules such as calcium or algae coenzymes.

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