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How to Lower Alkalinity in Your Pool (6 Effective Tips)

If your pool has high alkalinity, it can increase the pH and harm its chemistry. This combination results in stains, chemical buildup, and reduced chlorine effectiveness. Furthermore, it can raise calcium levels and cause itchiness, burning, and other unwanted side effects.

To lower alkalinity in your pool, follow these steps:

  • Test the pool’s alkalinity
  • Add dry acid or liquid acid
  • Do a partial drain and refill
  • Cover the swimming pool
  • Use lemon juice
  • Pour rainwater into the pool

Throughout this article, I’ll show you how to test and adjust your pool’s alkalinity. I’ll also provide a few alternative solutions and answer most of the common questions about swimming pool alkalinity levels.

Test the Pool’s Alkalinity

Before adding chemicals to the water, I highly suggest testing the alkalinity. Your pool’s pH and alkalinity are tied at the hip. If one of them goes up or down, the other follows. Check both components before adding any of the chemicals and additives suggested in this post. Fortunately, there are a few ways to test your pool’s chemistry.

Here’s a list of the three best ways to test a pool’s alkalinity:

Use test strips for a quick analysis of the water. The JNW Pool and Spa Test Strips show everything you need to adjust your pool’s chemistry. Dip a test strip in the water for about 30 seconds, then compare it to the seven chemicals on the bottle for ultra-fast results. The bottle also includes the recommended ranges.

  • Try chemical drops for an in-depth look at the pH, alkalinity, and other chemicals. The Poolmaster Essential Chemistry Set comes with multiple drops to monitor your pool’s progress. The drops are typically more accurate than test strips because you can adjust the quantity and size rather than relying on the test strip pads.
  • Consider digital testers if you want advanced water chemistry tracking data. Try the AquaChek TruTest Digital Reader for quick results. You’ll be able to see the alkalinity, pH, chlorine, and a few other details. These digital readers are much more accurate than traditional test strips because they don’t lose their effectiveness over time.

Pro Tip: If you’re stuck between these three solutions, I recommend going with the drops. They’re very reliable and sit in the middle of the price range. They also last longer in storage. However, test strips are effective in a pinch. Make sure you store all of your pool testers in a room temperature, dry location.

These three methods are quite effective, but they have widely varying prices. Find out which one suits your budget and needs, then try one or more of the alkalinity adjusters in the following subheadings. Remember to work in small doses to prevent the pH from dropping too quickly. You wouldn’t want to have to add soda ash or baking soda to bring it back up.

Add Dry Acid or Muriatic Acid

One of the best ways to decrease your pool’s alkalinity is to add acid. You can choose between dry acid and muriatic acid. Keep in mind that adding acid to the water will lower the pool’s pH level. However, you can make minor adjustments with baking soda or alkalinity increasers to raise the alkalinity if you drop it too low with the pH.

Below, I’ll break down the pros and cons of dry acid vs. muriatic acid.

  • Dry acid: Dry acid is the best choice for people with vinyl or fiberglass swimming pools because it’s not as harsh as muriatic acid. However, it needs to be mixed in a bucket, which takes a bit of time. You can get dry acid in much cheaper doses than liquid acid, making it a budget-friendly choice.
  • Muriatic acid (also known as liquid pool acid): Muriatic acid works quicker than any other acid in the pool industry. That being said, it needs to be thoroughly circulated, or it’ll stain and damage the swimming pool. It’s also much more corrosive, so you have to pay close attention when adding it to the water.

If you prefer dry acid, try EcoClean pH Down. This powder uses sodium bisulfate to quickly drop your pool’s pH and alkalinity. One 25-pound tub should last you several years, saving much more than if you used liquid acid. It also includes a helpful scooper to measure and adjust your pool’s chemistry easily.

On the other hand, the Champion AcidBlue Muriatic Acid is a great choice for quick effectiveness, easy dosage, and acid washes. You can use it to drop your pool’s pH and alkalinity within a couple of hours. There’s no need to dilute this acid. It’s uniquely designed to prevent harmful gasses from getting into the air.

Partially Drain and Refill the Water

Draining your pool and adding hose water will immediately alter its chemistry. You can use this process to your advantage if the alkalinity is too high. Hose water has a wide alkalinity range, so I recommend testing it beforehand. You can use the aforementioned pool water test strips, drops, and meters to check the hose water’s chemistry.

Here’s what you should know before draining and refilling the pool:

  • Work with one-foot increments. Draining and refilling the pool quickly alters a lot of the pool’s chemicals. For example, it dilutes chlorine, cyanuric acid, calcium, etc. I suggest testing all of the chemicals, draining one foot, adding one foot of hose water, then testing the chemicals after circulating the water for a few hours.
  • You might raise the alkalinity, depending on the hose water’s chemistry. Some hose water and well water have very high alkaline levels. Swimming pools should have alkalinity between 80 to 120. If you have highly-alkaline hose water, it’ll worsen the problem. Always test the source beforehand.
  • Never drain more than ⅓ of the pool at a time. Almost any swimming pool material will be damaged if it’s exposed to direct sunlight for too long. For example, vinyl will crack, the plaster will become porous, and fiberglass can cave in. The good news is that you shouldn’t have to drain more than a couple of feet.
  • Turn off your pool equipment before draining the water. Running your pool pump or heater without water moving through the plumbing will cause severe internal damage. The pump’s motor, impeller, and capacitor will overheat. Furthermore, the heater’s ignitor will skip and potentially trip the breaker.

Draining and refilling are some of the most effective ways to handle numerous swimming pool issues. It should be seen as a reset. You’ll likely have to add chlorine and a few chemical adjustments after refilling and testing the water. Consider spiking the chlorine to 5ppm to prevent the phosphates in the hose water from causing algae blooms.

Put a Cover on the Swimming Pool

Swimming pool covers are excellent when it comes to preventing pool chemistry alterations, evaporation, and chlorine loss. They also keep debris out of the water. I highly suggest anyone with a swimming pool should get a cover. You can use the cover all week to protect the liner and preserve your pool for many years to come.

So, why do solar blankets help you lower and maintain your pool’s alkalinity?

  • Solar covers prevent debris from getting into the water. All debris has varying pHs that influence your pool’s alkalinity. If there’s too much algae, leaves, pet hair, and other organic matter in the water, you’ll have a hard time maintaining the pH and alkalinity. Use a solar cover to keep the debris out of the pool throughout the week.
  • You can use a pool blanket to prevent your alkaline chemicals from evaporating. Pool covers keep the chemicals and water in the pool. You won’t have to add acid or soda ash to adjust the pH and alkalinity nearly as often if you have a cover. Furthermore, the alkalinity will promote chlorine effectiveness.

If you want a pool blanket, try the Sun2Solar Blue Solar Blanket. It’s a 12-mil cover that comes in multiple sizes and colors. The blue blanket is great at preventing evaporation, whereas the gray color retains the most amount of heat. Both options are available in round and rectangular dimensions.

Consider Using Lemon Juice

Lemon juice is naturally acidic. It’ll quickly reduce your pool’s pH and alkalinity. However, it’s important that you don’t go overboard. Adding too much lemon juice to your swimming pool can cause acidic corrosion and an increase in phosphates. Algae blooms thrive on phosphates, which is why you should keep the lemon juice to a lower dosage.

Keep these tips in mind when using lemon juice in a swimming pool:

  • Always run the pool pump when adding lemon juice to the water. If you don’t circulate the water, the lemon juice will corrode and stain parts of the liner. Lemon juice is very acidic, so it’s crucial that you turn the pump to its highest speed. You can also stir the lemon juice with a brush or dilute it in a five-gallon bucket beforehand.
  • Never add more than one gallon of lemon juice at a time. Lemon juice will quickly alter your pool’s chemistry. Too much of it will be problematic. Stick to half-gallon doses unless you have a massive pool. I often recommend people start with one cup of lemon juice poured around the skimmer basket for the best circulation.
  • You can pair lemon juice with other natural pH reducers. Lemon juice, rainwater, and many other additives will change your pool’s alkalinity without using harsh chemicals. Keep in mind that most natural remedies will add phosphates and nitrates, which means you’ll need to spike the chlorine to 5ppm.
  • Test your pool’s phosphates and remove all of the algae before using lemon juice. As mentioned above, adding lemon juice can increase the odds of an algae bloom. Algae blooms compound, so it’s crucial that you get the pool clean and clear before adding anything. Consider using a water clarifier to get the job done.

Pour Rainwater into the Pool

Rainwater is often acidic, which means it reduces the pool’s pH. As the pH goes down, the alkalinity goes with it. There are several ways to add rainwater to the pool, most of which require very little effort. Let’s explore the three best options below.

  1. Open the swimming pool whenever there’s a rainstorm. If you have a solar cover, take it off during the next rainstorm. Make sure you close the pool when it gets an inch or so below the top. The last thing you need is a flooded swimming pool. However, a couple of inches of fresh rainwater can make a massive difference.
  2. Collect rainwater in water collection barrels. Make sure it’s legal to collect rainwater in your area. If you’re allowed to, I suggest getting a barrel for rainwater collection to dump into the pool. Rainwater has a lot of phosphates for algae, but it can naturally control the pH and alkalinity. Rainwater also helps you dilute the water.
  3. Remove half of the solar cover and angle it toward the edge. If you want to reduce the alkalinity without taking the blanket off the pool, consider rolling half of it off. You’ll maintain some of the solar cover’s evaporation prevention while allowing rainwater and hose water to reduce the pH and alkalinity.

The Good Ideas Rain Wizard is a 50-gallon plastic barrel for rainwater collection. It includes a durable spigot to pour the water into a bucket and dump it into the pool. It comes in five colors, none of which will dent or scrape the ground thanks to their soft undercoating. Each barrel includes an optional connection to your roof’s gutters for quicker rainwater collection.

Pro Tip: Test your pool’s phosphates after adding rainwater. Phosphates can increase the likelihood of encountering algae blooms. It’s best to get the phosphates checked at a local pool store since the test strips can be a bit expensive. Don’t forget to test the pool water and add chlorine to 5ppm to prevent algae.

Does Baking Soda Lower Alkalinity In A Pool?

Baking soda doesn’t lower the alkalinity in a pool. On the contrary, baking soda raises the pH and alkalinity. You can add a pound of baking soda to a 10,000-gallon swimming pool to drastically increase the alkalinity in a pinch. However, alkalinity increasers and soda ash are much more effective in swimming pools.

If you want to raise your pool’s pH, baking soda can be an excellent substitute for soda ash. However, adding baking soda to a pool with high alkalinity will cause all sorts of problems. You’ll have to add a ton more acid to balance the chemistry. Not only that, but you’ll likely encounter cloudiness and stains.

The good news is that baking soda takes a while to dissolve, which generally means you can scoop it out of the pool. Never add pool acid to undiluted baking soda, though. You’ll cover the pool in a hazardous gas that takes a while to go away. Remove as much of the baking soda as possible and wait until the following day to add acid.

What Causes High Alkalinity In Pools?

High alkalinity in pools is often caused by adding hose water, using a salt cell, pouring liquid chlorine into the pool, and natural debris. Plants, pets, people, and fertilizers have varying pHs and alkalinities that influence your pool’s chemistry. It’s nearly impossible to prevent pH and alkalinity fluctuations.

Here’s an in-depth breakdown of why your pool’s alkalinity consistently goes up:

  • You have a saltwater pool. Saltwater has high alkalinity, which means your swimming pool will always need acid. It’s not uncommon to have to add dry acid or liquid acid weekly or every other week. Those with chlorinated pools often only need acid once per month or less, depending on various external factors.
  • Your pool is made of plaster (also known as gunite or concrete in the pool industry). Plaster has calcium, which naturally increases the pH. When the pH goes up, the alkalinity follows. Plaster pools don’t influence the pH and alkalinity as much as saltwater, but they play a significant role in your pool’s chemistry in the long run.
  • Your pool suddenly got extremely hot. Sudden, rapid temperature changes can affect the alkalinity and pH. Many pool owners expect to add acid at the beginning of spring and summer. Always test the pool before adding chemicals. The last thing you need is to have a constant battle of adjusting the pool’s chemicals.
  • Hose water almost always increases the pool’s pH and alkalinity. Anything you add to a swimming pool will affect the water’s chemistry. Check the pool’s alkalinity before and after adding rainwater or hose water. Most people have to add a couple of inches of water to their swimming pool each week if it’s uncovered.
  • Extreme algae blooms will influence the alkalinity. Algae is usually high in pH, which means it’ll elevate the alkalinity. Clear the algae, clean the filter, then test the alkalinity and pH. You might not have to add anything other than chlorine and algaecides to rid the algae. Chlorine could lower the alkalinity, too.

Will Alkalinity Decrease On Its Own?

The alkalinity will decrease on its own if you leave the pool cover off during a rainstorm. However, rainwater can add phosphates and nitrates to the water. They’ll bring algae blooms, which could increase the pH and alkalinity in the long run. It’s best to manually adjust the alkalinity to prevent it from harming the pool’s chemistry.

While your pool’s alkalinity can decrease by itself, it might take far too long. Your pool will be covered in stains and cloudiness. Furthermore, chlorine won’t be as effective as it should be. Those with plaster pools or saltwater sanitization might never have their alkalinity or pH go down without chemicals.

Another thing to remember is that fiberglass liners decrease the pH and alkalinity. If you have a fiberglass pool, you likely won’t need to use too much acid. Many pool owners combine fiberglass liners with salt generators to reduce how often they need to use soda ash, dry acid, liquid acid, etc.

Everything that goes in and out of the pool will decrease or increase the alkalinity. Some factors are much more influential than others. I recommend adjusting every component of your pool’s chemistry with chemicals. Many additives are natural, while others are designed for safe usage. Always take control of your pool’s alkalinity before it gets out of hand.

How Do You Lower Alkalinity Without Lowering pH?

You can’t lower the alkalinity without lowering the pH in a swimming pool. They go hand-in-hand, so adjusting one will adjust the other. Higher alkalinity will raise the pH and vice versa. An acidic pool will lower the alkalinity, too. It’s important to work in small increments since you don’t want to drastically alter either component.

Keep these three things in mind:

  1. It’s impossible to lower the alkalinity without altering the pH. Acid column slugs don’t work, even though countless pool owners have tried them. There are a couple of ways to balance the alkalinity and pH, but each of them takes multiple pump cycles. There’s no cure-all chemical for the pool’s chemicals.
  2. You can raise the alkalinity and pH with soda ash. Soda ash will mostly affect the pH, but it’ll slightly increase the alkalinity. You can use it if you accidentally use too much pool acid. This chemical is a go-to for nearly every pool owner because you’ll likely encounter low-pH issues.
  3. Alkalinity increasers will boost the alkalinity, but they also increase the pH a little bit. You can use them if the alkalinity is too low after using acid. Many people use tons of muriatic acid or dry acid to drop the pH and alkalinity, then soda ash or an alkalinity increaser to balance whichever chemical went too low.

Adjusting your pool’s alkalinity is a back-and-forth game. Once you balance them, it’s important to test them weekly. It’s much easier to make minor adjustments than fully reset your pool’s chemistry with soda ash and pool acid.