How Much Muriatic Acid to Lower Alkalinity in a Hot Tub? – 5 Steps to Use Muriatic Acid in a Spa


how much muriatic acid to lower total alkalinity of hot tub

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Fresh and healthy water in a hot tub is a must have requirement for our healthy and safe spa bath experience.

If the water in your hot tub is dirty or cloudy, it can cause several issues to your skin and overall health.

For example, soaking in a hot tub with poor water quality can cause you skin rashes, eye itching, and breathing problems as well.

I recommend you to check out this CDC.Gov article to understand the health risks of having a bath in unsafe and unhygienic spa or hot tub.

Most of the time when the water in your hot tub gets dirty, it’s because of the imbalance in its chemical equation.

It may be the too-high alkalinity of the tub that is causing the issue.

If this is the problem, then don’t worryt.

I have covered this topic specifically in this article just for you.

First of all, you need to understand that the average total alkalinity of your hot tub should be between 90-130 PPM.

If the concentration is higher than that, you will need to lower it down.

Obviously, I will be helping you do that in this article.

When the alkalinity of your tub is higher than printed value on your hot tub label, it can make the hot tub sanitizers and stabilizers of the tub go ineffective.

Also, it can cause green algae to grow in your hot tub, making it unhealthy for you to soak in.

Apart from the health issues, high alkalinity can also lead to scale buildup that will make your hot tub heating process slower than ever.

Trust me, you will just be waiting for your spa water to get warm for a long period.

Coming to the fixes, muriatic acid is one of the best ways to lower down your hot tub alkalinity, effectively.

Generally, you need to use 1.3 L of muriatic acid in 10,000 gallons of water to bring its total alkalinity down by 10 PPM.

If the current alkalinity of your 10,000-gallon hot tub is 170 PPM, you will need to use 5.2 L of muriatic acid to drag down the TA to 130 PPM.

Well, this is how you can use muriatic acid to lower your tub’s total alkalinity.

But that is obviously not all that you need to know about the relation between muriatic acid and your hot tub.

Thankfully, I am here to explain this topic in more detail so that next time you will do this acid mixing process much more prominently and confidently.

In the further sections of the article, I have mentioned everything that you need to know about muriatic acid and its effectiveness to reduce the total alkalinity of your hot tub.

Is It Safe to Use Muriatic Acid in a Hot Tub?

Using muriatic acid in your hot tub to lower its alkalinity is one of the best ways you can do for improving hot tub safety.

Also known as hydrochloric acid, this specific chemical is very corrosive and must be handled with utmost care.

If not, it can cause severe burns to your skin and even permanent eye damage.

However, you need to use this chemical for your hot tub safely and with proper care.

But how you can do it?

After several hours of deep research, I have come up with some simple tips that can help you lower your hot tub alkalinity using muriatic acid, without harming yourself.

3 Important Safety Tips for Using Muriatic Acid to Lower Your Hot Tub’s Alkalinity

Tip 1: Always wear eye glasses and gloves while using muriatic acid to lower your tub alkalinity.

Tip 2: Do every step gently and avoid backsplash because it might cause you burns.

Tip 3: Make sure to work in a ventilated place for the safety of everyone around you.

What Does Muriatic Acid Do for a Hot Tub?

Muriatic acid is mainly used to lower down the total alkalinity and balance the pH level of your hot tub.

When used, the chemical releases more hydrogen ions inside the water to lower the pH and the total alkalinity.

Also, it is used for cleaning your hot tub, killing the bacteria and algae present in it, and maintaining the proper pH of the tub’s water.

In some cases, muriatic acid is used with the hot tub for neutralization as well.

5 Steps to Properly Clean a Hot Tub with Muriatic Acid

As I mentioned in the previous section, muriatic acid is very effective in cleaning your hot tub.

So, continuing the point, let’s see how you can clean your hot tub with muriatic acid.

Before heading to the main cleaning steps with the acid, I would like to throw a light on some facts.

You will be surprised but every 6 out of 10 hot tub users do not change their spa water every month.

And they face different hot tub issues including the one we are talking about today.

If you change your tub water properly every month then you will hardly face any issues with hot tubs related to hygiene and skin infections.

However, I know that you have, somehow, gotten into the problem and now you need a quick fix.

So, here are 5 easy steps using which you can clean your hot tub with muriatic acid at your home.

Step 1: First step is to completely drain your hot tub.

Step 2: As per the dose, add a certain amount of muriatic acid to the hot tub’s water.

Step 3: Once the acid is diluted at 50%, then take a cleaning brush and scrub the part of the tub you want to clean the most.

Step 4: While doing this, be careful and wear eyeglasses and gloves, because of the highly corrosive nature of this acid.

Step 5: In the end, after cleaning everything properly, refill the tub with clean and pure water.

And that’s it!

Cleaning your hot tub with muriatic acid is as simple as cleaning it with a detergent.

The only thing you need to take care of is your skin and body parts by safeguarding them eye goggles, gloves and masks.

Recommended Articles for You:

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3 Safety Tips to Follow Before Adding Chlorine to Your Hot Tub

Can I Use Muriatic Acid to Clean a Hot Tub Filter?

Yes, obviously you can. When I said that you could use muriatic acid to clean your hot tub, I also meant the hot tub’s filter.

The filter is the part in your tub that keeps the water inside fresh and prevents formation of bacteria and algae.

Here are 4 simple steps that you can use to clean the hot tub filters using muriatic acid.

Step 1: Take the muriatic acid and apply a few drops of it to the hot tub filter.

After few seconds, the acid will start to bubble, let it happen.

Step 2: Then, soak the cartridge filter using the acid and the water.

The ratio of muriatic acid and water in this process should be 1:10 (1 part muriatic acid and 10 parts water)

Step 3: Let the filter dry for 3-5 hours properly.

Step 4: After 3-5 hours are over, then rinse the hot tub filter with clean water properly.

Note: If the filter is very dirty or has a buildup on it, you may need repeat the above process a 2-3 times.

How Much Muriatic Acid to Use for a 400 Gallon Hot Tub?

This is where many hot tub owners get stuck.

How much muriatic acid to use for a 400-gallon hot tub?

Not only for a 400-gallon hot tub, the question remains the same for every small sized and compact hot tub.

By now, you already know how much muriatic acid you should use for a 10,000 gallons hot tub.

But for a 400-gallon hot tub? I think you might still have some confusions, am I right?

But worry not, I have already done some research and trials with my hot tub to get to a proper conclusion.

From this research, I can tell you what amount of muriatic acid you actually need to lower the total alkalinity of your 400-gallon hot tub.

As we all know, you need 1.3 L of the acid to drag down 10 PPM from a 10,000-gallon hot tub.

Following the same formula, you will require 0.052 L (1.75 Oz) of muriatic acid to lower down 10 PPM from a 400-gallon hot tub.

How Do I Bring the Alkalinity Down in My Hot Tub Naturally?

After reading the whole article about lowering your hot tub alkalinity using muriatic acid, you would find it hard to believe that you can also do it naturally.

Yes, you can do it without using any chemicals too.


Simple, the answer is White Distilled Vinegar.

Sounds amazing, right?

You can actually lower your hot tub’s total alkalinity using simple white distilled vinegar which is also being used at your home.

Just take a few cups of vinegar available in your home and add it to your hot tub.

Then circulate the hot tub water properly (you can keep the jets open for better circulation).

And guess what, you are done.

This will keep lowering the TA of your tub gradually.

Though vinegar does not lower the alkalinity suddenly or to a great extent, yet it still works.

If you want to balance the chemical equation of your tub without using any chemicals, white distilled vinegar is the safest natural solution for you.

Muriatic Acid Hot Tub Calculator to Lower Alkalinity

The muriatic acid hot tub calculator is a simple online tool that lets you know how much muriatic acid you need to add to your tub to lower or raise its total alkalinity.

To calculate the amount, you need to enter your hot tub volume and the last alkalinity level you got from its pH testing.

And then enter the alkalinity level that you want to achieve.

After doing this, click on calculate to know how much muriatic acid you will need to lower down the TA of your tub to a certain level.

It’s super easy.

In case you are looking for a trusted hot tub alkalinity calculator, then click here to calculate your hot tub’s Total Alkalinity level.


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