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Muriatic Acid for your Pool

Managing the alkalinity levels in your pool water can sometimes seem like a daunting task that requires a Ph.D. in chemistry or a wizard’s hat and profound knowledge of alchemy. It doesn’t have to be this way.

High alkalinity can actually be easily resolved with a common (and inexpensive) additive: muriatic acid. It’s not as simple as just dumping it in your pool, however. Let’s dive in and see how a dash of muriatic acid will clear up your alkalinity troubles, hassle-free. 

What is Muriatic Acid?

Muriatic acid, also known as hydrochloric acid, is an acid that is naturally produced in the human body, believe it or not. It’s also used in a number of commercial cleaning, production, and building processes, produced by dissolving hydrogen chloride gas in water.

It is a highly-corrosive acid with lots of uses, benefits, and indications but around the pool or hot tub, just one. When it comes to a backyard swimming pool, muriatic acid is used to lower the alkalinity and pH of your pool or spa water. 

pH, Demystified

You don’t have to be a professional scientist to understand pH. It’s a simple scale that really comes in handy when trying to diagnose issues with your pool water chemistry. The abbreviation “pH” stands for “potential hydrogen” and forms a scale that goes from -5 to 14.

The low end of the scale are acidic substances and the high end are basic. Neutral, which is the pH of pure water is a 7 on the scale. The scale is actually logarithmic, which means that every number signifies a change of 10 times the previous value. 

The Dependent Relationship Between pH and Alkalinity

pH and alkalinity are like that weird couple that goes everywhere and does everything together. They’re so intertwined that whenever you mention one, you can’t help but talk about the other. 

pH and alkalinity work similarly too. Whenever the alkalinity or pH levels in your pool water change, the other will inevitably follow suit. 

The reason behind this is the instability inherent in your pH levels. Much like that weird couple we all know, one member of the duo is naturally a little more unstable and the other balances them out. Maintaining proper total alkalinity levels in your pool helps to keep your pH levels from fluctuating by acting as a stabilizer or a buffer.

Nobody likes fluctuating pH.

So whenever you bust out your pool chemistry kit, remember that anytime you raise or lower one, the other will follow. This goes double for pH. Because a proper alkalinity level is the buffer, whenever your alkalinity levels change, the pH will drastically change in the same way, either higher or lower. 

The Dangers of Unbalanced pH & Highly-Alkaline Pool Water (or How to Avoid Being Basic)

Nobody wants to be basic, especially your pool. The term “basic” doesn’t mean you’ll find a pumpkin spice latte or a new pair of Ugg boots floating in your pool every morning, it actually refers to your pool’s pH level.

When the pH level is above neutral (7) the water is considered “basic”. 

If the worst happens and your pool becomes too basic, your water can get nasty and flaky, not to mention it becomes susceptible to calcium buildup, which can damage your pump system. A clogged filtration system can lead to all kinds of problems from improperly cleaned water, like algae and bacterial growth — yuck.

You may have already encountered a calcium buildup or mineral scale clog in your system. If you’ve recently had to add more chlorine than usual or a higher pH when testing your pool water, then high alkalinity could be to blame.

The good news is that the alkalinity of your pool water will actually self-correct over time. 

Depending on how high your total alkalinity is, you may be able to wait a few days for it to sort itself out. Sometimes, however, this is not a good idea, opening your pool up to system damage, algae infestation, and a whole lot more chemicals to fix the problem in the long run.

Where Your pH and Alkalinity Should Be, Ideally

Strangely enough, we do actually want to aim for a bit of a basic pH for the perfect pool water. The sweet spot is between 7.4 and 7.6. It’s a small range, mostly because big changes in pH can wreak havoc with your other pool chemicals.

The happy place for pool alkalinity falls within a range of 100 and 150 ppm (parts per million), where 125 is the best possible place to be.

How to Add Muriatic Acid to Your Pool

To start, it’s a good idea to grab all of the materials you need. It’s not a big project, but everything goes much more quickly when you have all your stuff together.

What You’ll Need:

  • Pool water test kit
  • Safety goggles
  • Acid-resistant gloves
  • Chemical-resistant apron
  • A big plastic bucket
  • Wooden or plastic stir stick
  • Oh yeah, some muriatic acid too

Muriatic acid is an acid, after all. Following some simple safety precautions as you work will protect your eyes, skin, and clothes from an unfortunate accident. You may feel like Dr. Horrible when you’re all geared-up, but just play along with it. Being a mad scientist for a day sounds pretty cool actually.

Make sure not to even breathe a whiff of the acid solution — the vapors can cause serious respiratory problems.

A Note on Safety

It’s a good idea to get in the habit of becoming acquainted with any chemicals you actively use. I’m not saying you have to take them out to dinner or anything, but you should have a good idea of what they do.

It’s not terribly difficult, even if you’re not an amateur chemist. I highly suggest pulling up the information yourself instead of asking around on forums or your Uncle Steve who constantly says, “Back in my day, we just hucked a gallon in and it worked fine.”

Don’t listen to Uncle Steve.

Every chemical sold and manufactured in the US has an MSDS (Material Safety Data Sheet). If you’re outside the US, there should be an equivalent Safety Data Sheet. It tells you everything you’ll need to know about the chemical, including safety precautions necessary. There’s more information than the average user will need, but you’ll want to pay special attention to safety and proper PPE (Personal Protective Equipment).

The MSDS tells you exactly what kind of protection you’ll need, and what to do if the worst happens. Sometimes a simple set of dishwashing gloves will suffice, but you won’t know until you take a look.

Don’t be like Uncle Steve. He’s always been a little off anyway. 

Start By Testing

Before you even think about adding any chemicals to your pool, you need to test the water. This goes for chlorine, cyanuric acid, or any other chemical you use on a regular or not-so-regular basis. Grab your pool water test kit or testing strips and do your thing.

Once you have a baseline of where all of your levels are, then you can determine what you need to add and in what quantities. Strap in, though, because no matter what your test results say, adding muriatic acid to your pool is going to be an all-day endeavor.

Math! Determine How Much Acid You Need

To save you from using too much acid or not enough, it’s a good idea to actually calculate the precise amount of muriatic acid that you’ll need, based on the capacity of your pool. 

If you know the volume of your pool — perfect! You’re nearly there. Most bottles of muriatic acid will let you know how much you need to use for different pool capacities. 

If you don’t know the number of gallons of water in your pool, you can use a handy pool calculator to figure it out yourself. Once you’ve done the math, you can move on to the next step, safe in the knowledge that you’re using the right amount.

Turn Off Your Pump

This may seem like a strange thing to do since, as a pool owner, you know how important water circulation is to overall pool health and sanitation. In this case, however, it’s all about oxygen. Circulating water through the pool pump causes aeration or oxygenation to occur in the water.

Oxygen combined with muriatic acid is a potent combination that causes a massive reaction, significantly affecting your pH. The goal is to balance and buffer the pH of your pool water, not give it a panic attack.

So, when adding muriatic acid to your pool, we need to limit the amount of oxygen that gets to interact with the acid, moderating the chemical reactions that can occur between the two chemicals. Turning off the pump for this step is the best way to avoid this situation.

Add the Muriatic Acid to the Pool

This project is a marathon, not a race. Take your time here and don’t just toss the acid into your pool. Doing so could cause serious injury if you accidentally splashed any acid on yourself or your pool equipment.

The best method of adding muriatic acid to your pool is to dilute it in a bucket of water at a ratio of 10:1. That’s 10 parts water, 1 part muriatic acid. Make sure to fill the bucket with water, before adding the acid to avoid a nasty surprise in the form of a chemical reaction.

Once you have your mixture combined in the bucket, you can either pour it into the deep end of your pool or walk around the edges adding it slowly bit by bit. Whichever way you choose, make sure you’re wearing your goggles and gloves to protect yourself from unintentional sloshing.

Choose Your Own Adventure

Pool maintenance might not be the most exciting thing in the world to do on your Saturday afternoon, so let’s pretend we’re going on a quest. The next stage of your journey happens to be a fork in the road where you must now choose which path to take. Choose wisely, my friend.

If you take the path to the right, you can simply add the muriatic acid, turn your pump back on, and let the pump do all the work of moving the acid around, gradually lowering your pool’s alkalinity and buffering your pH.

If you take the path to the left, a bit more sweat and toil will be expected of you. After adding the mixture to your pool, take hold of your long-handled brush and periodically sweep the floor of your pool as the acid does its work. Without this labor on your part, the corrosive acid could eat away at the floor of your pool, causing untold damage.

The choice is yours.

Aerate the Pool 

If you know your pH is on the lower end of the healthy scale, you can also choose to aerate your pool. As we mentioned before, the oxygen and muriatic acid combination will have a quick effect, reacting together to raise your pH faster than it would without the bubbles.

If you chose to use your pump to circulate the muriatic acid, you can just leave it running a bit longer to help to boost your pH. For an even more effective (and faster-acting) boost, turn on any aerators, fountains, or other water features you may have to enhance the effects.

Retest the Water (In the Morning)

After a refreshing sleep and a good hearty breakfast, the time has come to retest your water and see where you stand. Has it all been worthwhile? Is your alkalinity lowered and your pH stable? There’s only one way to find out. Grab your test kit and do your thing. 

Hopefully, your alkalinity and pH are now within the recommended levels and all is right with the world. However, if your alkalinity hasn’t decreased enough, you can start again from the beginning and repeat the process until your alkalinity is where it needs to be (between 100-150 ppm).

If your alkalinity is perfect but your pH is still too low — more aeration is the solution. Keep your pump, fountain, waterfall, or aerator running for another day to give the oxygen a chance to help increase the pH naturally.

Test again the next day and if the pH is still too low, you can always use a pH increaser to get you back to where you need to be.

Alkalinity & pH In Perfect Harmony

This entire process can be repeated as often as you need to in order to properly balance your pH and alkalinity levels in your pool. 

Now you can be a mad scientist as often as you need to in order to keep your pool free of algae, bacterial growth, corrosion, and staining that go hand-in-hand with wonky water chemistry. 

Once your pool water is properly balanced, you can go back to enjoying your beautiful pool completely worry-free.

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