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How to Lower the pH Level in a Pool: The Complete Guide

Lowering the pH in your pool is a must-know technique that can prevent cloudiness, calcium buildup, and skin irritation.

Most pool chemicals require an optimal pH between 7.2 to 7.8, so it’s crucial that you know when it’s time to regulate the range. Some pools are more susceptible to having a high pH level than others.

To lower the pH level in a pool, follow these instructions:

  • Add muriatic acid
  • Use dry acid
  • Consider sulfuric acid
  • Control the alkalinity
  • Use algae treatments
  • Apply a citrus cleaning solution
  • Try chlorine tablets
  • Reduce the pool’s salinity
  • Switch to a fiberglass lining
  • Keep the pool clean and clear
  • Opt for natural pH reduction solutions

In this article, I’ll dive into every method you can try to lower your pool’s pH that I’ve found during my years as a pool technician.

I’ll also share tips and tricks for maintaining direct pH, indirect pH, and alkalinity, so you can regulate your pool’s chemistry whenever you need to. Let’s get started

Add Muriatic Acid

Muriatic acid is the most effective way to lower your swimming pool’s pH.

Not only does it dissolve quicker than any other pH treatment, but a little bit goes a long way. Most people don’t need to add more than a gallon to manage their pool’s pH. However, extremely high pH and alkalinity levels could call for a slightly higher dose.

According to HGTV, muriatic acid dissolves quickly because it’s a liquid with a similar consistency to water. You don’t have to worry about cloudiness, buildup, and so on.

Furthermore, the liquid can be used to acid wash the bottom of an empty plaster pool. Acid washing lowers the plaster’s pH and strips the top layer.

Muriatic acid is one of the harshest chemicals you can put into your swimming pool. Keep these factors in mind before using it:

  • Only use the recommended amount per dosage, and don’t add more than one dose per 24 hours. Muriatic acid is very effective, so you don’t want to lower the pH to unhealthy levels. You’ll have to use soda ash to increase your pool’s pH, costing more time and money than necessary.
  • Muriatic acid is highly corrosive. Never dump it directly into the skimmer basket, pump basket, or anywhere near the equipment. It can shred a hole through metal, plastic, and many other materials if it sits there for too long. Always wear protective gloves, glasses, and long-sleeve clothing when using muriatic acid.
  • You shouldn’t use muriatic acid in vinyl liner swimming pools. It’s too harsh for the vinyl, so it can crack and destroy it. The liquid acid can also break apart the corrugated plastic hoses and make its way into the equipment. I highly recommend using dry acid instead, which I’ll discuss later in this post.
  • People with salt pools and newly replastered pools should expect to use a lot of muriatic acid. These pools are prone to having a high pH, making liquid acid a necessity. The calcium in the new plaster layer increases the pH, and you also have to add more calcium to prevent damage for the first couple of months.
  • Always add muriatic acid while the pump is running (and make sure to add it around the edges of the pool). Pump circulation is crucial when using muriatic acid because it prevents corrosion and ensures even distribution throughout the water. If you don’t run the pump for at least a few hours after adding muriatic acid, it will burn the bottom of your pool.

Muriatic acid is incredibly useful and perfectly safe when used properly. However, some pool owners are understandably concerned about its corrosiveness and off-gassing dangers. Therefore, I’d like to discuss an alternative that’s nearly as effective as liquid pool acid.

Consider Using Dry Acid Instead of Muriatic Acid

Dry acid is the preferred choice for those who have pets, children, and vinyl liners. It’s also convenient because you don’t have to worry about gaseous fumes or instant corrosion.

Furthermore, dry acid is often used in spas, so you can use the same container for your swimming pool and hot tub.

EcoClean Solutions pH Down is an excellent dry acid that quickly reduces your pool’s pH.

One pound is enough to treat up to 10,000 gallons, so you’ll have more than enough in this 25-pound bucket. You can opt for a 50-pound bucket since the dry acid doesn’t have an expiration date, and the airtight seal is great for safety and preservation purposes.

While dry acid is an optimal choice for many pool owners, it has two notable drawbacks:

  1. Dry acid can make the pool a bit cloudy for 30 to 60 minutes. The granules take a while to dissolve, so it’s crucial that you circulate the pump to prevent them from settling. However, this issue is merely a visual concern, and it’ll go away soon enough. Always evenly distribute the dry acid around the edges of the pool.
  2. You have to dilute dry acid in a bucket before using it. Grab a five-gallon bucket, fill it with a couple of gallons of water (you can scoop it out of the pool or fill it with a garden hose), then pour the required amount of dry acid into the bucket. Stir it with a large spoon or ladle and dump it into the pool.

Dry acid isn’t necessarily worse than muriatic acid, it just requires different (and often lengthier) steps. You can lower the pH with either dry acid or muriatic acid without any issues if you follow the provided instructions.

That being said, there’s a third alternative that pool owners are now leaning toward.

Try Sulfuric Acid to Reduce the pH

Sulfuric acid is often known to be highly corrosive and dangerous to handle. However, its dissolvability and low pH value make it a prime candidate for swimming pools.

You should know that sulfuric acid should be handled with extreme caution, so I suggest hiring a professional during the first few applications until you learn the ropes.

There are plenty of pros and cons to using sulfuric acid in your pool:

Pros of Sulfuric Acid for Swimming Pools

  • Most sulfuric acid containers don’t off-gas, produce foul odors, or leak into the air.
  • There aren’t as many dangerous fumes to inhale as muriatic acid.
  • Sulfuric acid is typically more affordable compared to muriatic acid.

Cons of Sulfuric Acid for Swimming Pools

  • Sulfuric acid isn’t nearly as readily available as muriatic acid.
  • It can burn your skin, eyes, and hair instantly.
  • This acid can strip the metal or plastic off of your pool equipment if it’s not handled properly.
  • Most experts recommend hiring a pool service or professional to handle sulfuric acid.

There are also debates about whether sulfuric acid increases the probability of algae blooms. It adds sulfates and total dissolved solids to the water, which eventually renders the algaecides and chlorine less effective. However, the TDS and sulfites are often diluted by natural evaporation and refilling of the water.

Personally, I’d rank pH reducers in the following order from best to worst:

  1. Muriatic acid (unless you have a vinyl pool).
  2. Dry acid
  3. Sulfuric acid

Remember that your pool’s pH is tied to its alkalinity. You’ll have to manage both factors to prevent the other from deviating.

Manage the Pool’s Alkalinity

Increasing the alkalinity will increase the pH, whereas decreasing the alkalinity will decrease the pH.

Your pool’s alkalinity should range between 80 to 120. When the alkalinity is too low, you have to add baking soda. When the pH is too low, you need to add soda ash.

The convenient part about lowering the alkalinity and pH is that they both use dry acid or muriatic acid, so you usually don’t have to buy a second chemical to treat the alkalinity apart from the pH.

However, this process can create chemical balancing issues. For example, you might raise the alkalinity too high, making it misaligned with the pH. You’ll have to go back and forth between adding baking soda and muriatic acid to get the right balance.

Here’s what you need to know about the balancing act between reducing the alkalinity and pH in your swimming pool:

  • Always manage your pool’s pH and alkalinity in small increments. Your goal should never be to change the pH by more than .5 per treatment. The alkalinity will slightly adjust with the treatment, so it’s important to test both of them after 24 hours. Wait a full day before adjusting either measurement.
  • Muriatic acid is the best treatment for extremely high alkalinity and pH in a pool. Acid Blue Muriatic Acid is highly effective when it comes to dropping both measurements. Each container is made with a unique plastic that reduces off-gassing vapors by up to 90%.
  • If you drop the alkalinity too much, but the pH is too low, you should use baking soda instead of soda ash. Baking soda drastically increases the alkalinity while slightly moving the pH, while soda ash quickly increases both measurements. To make sure you’re prepared for any situation, I suggest keeping muriatic acid, baking soda, and soda ash in your pool chemical shed at all times.

The good news is that your pool’s pH and alkalinity are incredibly easy to manage once they’re balanced.

Solar covers suppress natural pH adjustments, letting you keep the pH and alkalinity in the desired range until you remove the cover. Always cover your swimming pool when it’s windy or rainy to keep phosphates out of the water.

Use Algae Treatments

Algae typically increases your pool’s pH and alkalinity. Most bacteria can’t thrive in acidic environments. Additionally, your pool’s chlorine works best when the pH and alkalinity are balanced. Eliminating all of the algae blooms in your swimming pool will make it much easier to lower the pH without too much acid.

There are countless algaecides on the market, but most of them are labeled as preventatives. Make sure you know if you’ve purchased a preventative or an algae killer before adding it to the swimming pool. Algae preventers remove algae’s food source, but it takes much longer to get rid of existing blooms.

The Coral Seas Green to Clean is my top choice when it comes to eliminating large algae blooms. It’s incredibly effective and leaves your pool looking clean and clear. One 4-pound jug is enough to treat up to 30,000 gallons of water. You have to use Green to Clean with pool shock for maximum effectiveness.

Here’s the process of using Green to Clean:

  1. Add two pounds of Green to Clean to the water.
  2. Immediately add two pounds of powder pool shock.
  3. Circulate the pump for 24 hours.
  4. Repeat steps 1 and 2.
  5. Circulate the pump for another 24 hours.

You’ll likely have to clean your pool filter when you’re done using any algae killer. The dead algae often makes the pool cloudy and clogs the filter media.

Algae preventatives are also quite useful. They’re not as common as algae killers because most pool owners don’t know chlorine isn’t always enough to manage a pool. The hot days of summer often evaporate the chlorine, but copper-based algaecides take much longer to evaporate than chlorinated water.

Pro-tip: Test your pool’s copper levels regularly. Stop using copper-based algaecides if the metal levels are too high. Too much copper can cause staining and other issues.

Apply Citrus-Based Stain Removers

Citrus is a highly-effective treatment against algae because it’s often acidic. Furthermore, it lowers the pH and creates a dangerous environment for bacteria and algae growth. Many companies offer citrus-based stain removers because they get rid of algae stains, chemical buildup, calcium deposits, and more.

The Bosh Chemical Vanish Pool & Spa Stain Remover uses citrus to eliminate most stains from numerous sources. Each two-pound container treats pools up to 20,000 gallons. You can use this treatment in vinyl and fiberglass pools since it’s non-corrosive. It’s an excellent treatment for rust spots, too.

If you don’t want to purchase a citrus-based stain remover to lower the pH, lemons from the grocery store provide a great natural alternative.

Follow these instructions to eliminate stains while lowering the alkalinity and pH in your pool:

  1. Cut a lemon in half and dive into the pool.
  2. Scrub the lemon against the stained area, then scrub it with a pool brush.
  3. Repeat the process until the stain is gone.

Note: You can also scrub the stain with a chlorine tablet since it lowers the pH and kills the algae. However, this method isn’t useful when it comes to removing calcium deposits. Lemons and chlorine tablets can be used to eliminate black algae that corrodes the gunite and hides on the porous surface. Trapped black algae slowly increase the pool’s pH.

Opt for Chlorine Tablets Instead of Liquid Chlorine

Liquid chlorine is undoubtedly the most popular way to chlorinate a swimming pool. It’s cheap, easy to use, and quickly dissolves in the water.

However, liquid chlorine has a pH between 11.0 to 13.0, which means you’ll constantly have to battle it with acid.

Fortunately, liquid chlorine is much less concentrated than soda ash, so it doesn’t boost the pH to uncontrollable levels.

That being said, those dealing with high pH pools should opt for chlorine tablets. Chlorine tablets have a pH of around 2.0 to 3.0, so they quickly boost the pool’s acidity. Furthermore, you can swim with chlorine tablets in the pool, unlike a fresh treatment of liquid chlorine.

Unfortunately, chlorine tablets are often misused. To make sure you’re on the right path, here are a handful of treatment reminders to prevent the pH from dropping too low or the chlorine from getting too high.

  • Only use one chlorine tablet per 5,000 to 10,000 gallons of water (unless the manufacturer’s instructions say otherwise). Chlorine tablets dissolve in about 5 to 10 days. Filler-packed tablets dissolve much faster than high-quality tablets. Too many tablets will make you have to reduce the chlorine levels and cyanuric acid and increase the pH.
  • Don’t use chlorine tablets if your swimming pool’s cyanuric acid is above 100. Cyanuric acid is like sunscreen for your chlorine. It prevents excessive chlorine evaporation. However, too much of it makes the chlorine ineffective and can drastically alter the pool’s pH.
  • Get a chlorine floater that has an adjustable set of holes to let you manage the acidity and chlorine concentration. The Swimline Chlorine Dispenser is lined with multiple holes to help you open and close it as needed. You can load up to five chlorine tablets into the floater. Tighten the lid after adding the tablets, and you’ll be good to go.

Lower the Pool’s Salt Levels

Pool salt is a chlorine alternative that uses salt cells to break apart the chemical compounds in your pool.

As salt goes through the salt cell, it’s spliced into sodium and chlorine. Both of these treatments have a high pH, so salt systems naturally increase your pool’s pH. Those with salt systems should expect to use muriatic acid or dry acid bi-weekly.

However, you can get salt into the pool without having a salt system.

For example, liquid chlorine uses sodium hypochlorite. The sodium in this chemical compound stays in the pool, while the chlorine evaporates when it dissolves into the water.

Note that reducing your pool’s salt levels will drop the pH and alkalinity.

Here’s the step-by-step process to get rid of the salt in your pool:

  1. Test your pool’s salt levels. Salt increases the TDS, which makes it difficult for pool acid and soda ash to dissolve in the water.
  2. If the TDS exceeds 2,000ppm (or the salt is above 3,500ppm in a saltwater pool), it needs to be partially drained. I typically recommend draining the pool by a foot or so, then refilling it.
  3. Test the TDS and salt levels after refilling the water, then perform the previous step again if necessary. Never drain more than ⅓ of your pool at a time, and make sure the pump is off to keep air bubbles out of the plumbing.

Dealing with salinity in the water is an inevitable part of owning a swimming pool.

To help you keep track of your salinity levels, I recommend dipping the ORAPXI Digital Salt Tester into your pool and checking the levels once per month. This meter can also test the TDS and temperature of your swimming pool. All of this will help you adjust the pool’s pH without wasting the chemicals.

Switch to a Fiberglass Lining

Fiberglass pools have the opposite problem as replastered pools: They reduce the pool’s pH. You’ll likely have to add soda ash or baking soda every few weeks. However, many pool owners combat this common issue by installing a salt system. Salt cells raise the pH, while fiberglass liners drop the pH. The result is a balanced pool without many chemicals needed.

You can hire a professional to install a fiberglass liner in your swimming pool or get a brand-new fully-fiberglass pool.

Maintain a Clean and Clear Swimming Pool

Maintaining a clean and clear swimming pool removes the debris from your pool, prevents algae blooms, and eliminates calcium buildup. All three of these benefits help you regulate the pool’s pH and alkalinity.

Without a clean and clear pool, you’ll likely have to add soda ash and muriatic acid weekly.

Fortunately, your pool is much easier to maintain when the chemicals are balanced.

I always recommend the following weekly routine to keep your pool in check to preserve the proper pH and reduce unwanted high alkalinity levels:

  1. Test your pool’s chemistry weekly. Set a routine schedule and always test the water on the same day. Add the necessary chemicals to keep the chlorine between 2ppm to 5ppm, the pH between 7.2 to 7.8, the alkalinity between 80 to 120, and the calcium hardness between 200ppm to 400ppm.
  2. Remove all of the debris and algae from your pool as quickly as possible. Most natural debris will reduce your pool’s pH, but it can encourage algae growth. Since algae increase the pH, it’s quite dangerous for the water. Weekly brushing is an excellent way to prevent blooms, too.
  3. Drain your swimming pool ⅓ of the way if the total dissolved solids exceed 2,000ppm. The TDS in your pool saturates the water, much like stirring a powder drink formula into a glass of water. Too much TDS eventually makes it impossible for the rest of the chemicals to dissolve in the pool, making them ineffective.
  4. Clean your filter whenever the gauge goes over 25 PSI. A clogged filter will limit the pump’s performance, preventing it from circulating the pH adjusters. Furthermore, it’ll allow algae to grow and boost the pH to dangerously high levels. Don’t forget to dump the debris out of the skimmer basket and pump basket three times a week.

Your pool’s clarity is directly related to its pH. If the water has a high pH, the pool will look cloudy. Vacuuming, circulating, and maintaining the pool water is integral to keeping the pH and alkalinity levels in the proper range.

How To Lower pH In Pool Naturally

Lowering your pool’s pH naturally prevents you from using harsh chemicals (including muriatic acid and sulfuric acid).

You can effectively reduce the pH and swim in the pool almost immediately with many natural solutions. Keep in mind that most natural treatments take a bit longer than using pool chemicals.

So, how can you lower your pool’s pH naturally? Try these suggestions:

  • Add a gallon of lemon juice, white vinegar, or apple cider vinegar. These liquids are quite acidic, which means they quickly lower your pool’s pH. Dump up to one gallon of one of the liquids into the pool and circulate the pump for 24 hours, then test the pH. Remember to maintain the pool’s chlorine levels to prevent algae blooms from the lemon juice.
  • Dilute the high pH in the swimming pool with hose water, well water, or rainwater. You can collect rainwater and dump it into the pool to drastically reduce the pH and alkalinity. Most local water sources have varying pH, so it’s important to know your source’s pH before diluting the water.
  • Drain and refill the swimming pool. Draining the pool is an extreme measure that should only be attempted if your pool has high total dissolved solids (TDS), salinity, calcium hardness, or an uncontrollable pH problem. Never drain more than ⅓ of the pool if you want to avoid liner cavitation and cracks.
  • Install a CO2 tank or distilled water tank to the plumbing. Both of these pieces of equipment naturally reduce the water’s pH without requiring much intervention. Hire an expert to install either of these tanks since they both call for warranties and licensed installations.
  • Brush and vacuum calcium deposits out of the swimming pool. Calcium hardness levels can lead to deposits all over the gunite. This buildup is easily removed with abrasive brushes, but it’s important to vacuum the cloudiness to prevent it from getting back into the water. Reducing the calcium in your pool makes the pH easier to manage.

There are plenty of ways to reduce your pool’s pH naturally. While they don’t lower the alkalinity as drastically per treatment, they’re worth trying if you don’t want to use harsh chemicals.