How To Lower pH In A Hot Tub: Soda Ash Or Baking Soda?

pH, which is an acronym for Potential Hydrogen, is a scale that shows the measure of the concentration of hydrogen ions in a solution, in this case, your hot tub water. Simply put, it tells you how acidic or basic the water in your hot tub is. 

On a scale of 0 to 14, with 7 representing a neutral solution, values above 7 indicate a basic or alkaline solution, while values below 7 and decreasing indicate an increasing acidic solution as the value drops down. 

So if the pH of your hot tub is low or has dropped down, it is time to increase it back to a more ideal level if you do not want to expose yourself and other users of the hot tub to potential risks associated with acid water.

So, how do you lower the pH in a hot tub? Do you use soda ash or baking soda? Well, between soda ash and baking soda, none of them can lower the pH of hot tub water. 

Soda ash, similar to baking soda, is the complete opposite and will do the reverse when added to your hot tub. They are alkaline substances and can only increase the alkalinity in your spa.

Does Soda ash lower pH in hot tubs?

Soda ash, the common name for sodium carbonate, does not lower pH. Rather, having a very high pH between 11.3 and 11.7 increases pH when added to a medium.

Adding soda ash to the water in your hot tub will raise both the pH level and the total alkalinity of the water. And this will require the addition of an acid to create balance. 

So, bottom line, soda ash is not used to lower hot tub pH. And even when used to raise the pH level in a hot tub, it can be a bit complicated to use and get the right results.

What are the causes of high pH in a hot tub?

When you add too much pH into your hot tub while trying to raise the pH level, you can end up with a higher pH than the recommended normal.

Regular shocking of hot tub water also causes a spike in the pH level. So if you just finished shocking your hot tub, there is a good chance that the pH level of the spa water is high. So you should treat them accordingly.

Other causes of high pH in the hot tub include your water source, exposure to rain, and the atmosphere, as well as dissolved fluids from people when they soak in the hot tub. To learn more about the causes of high pH in hot tubs, read this article: “The Causes of High pH In Hot Tubs?

What are the effects of high pH in a hot tub?

Unbalanced water chemistry in your hot tub, whether high or low pH, will always negatively impact your hot tub and its users.

If your hot tub pH is high and it is not lowered to an ideal level, here are some of the things that will happen.

  • Visually, instead of the blueish, crystal clear watercolor of healthy water, your hot tub water will become cloudy. This is a result of the high amount of undissolved calcium or calcium coming out of the solution.
  • Scales will start forming on the inside of your hot tub walls, on the water surface, and inside the hot tub pipes. This is a result of the formation of calcium carbonate as a result of the excess calcium in the water combined with carbon dioxide.
  • Hot tub pipes and filters will begin to get clogged. This can lead to damage to the water pump as a result of built-up pressure.
  • Users of the hot tub will experience itchy eyes and skin when using the hot tub. Worst case scenario, it can lead to respiratory issues for some people.
  • Your hot tub is going to require the frequent addition of sanitizing chemicals to keep up with the increasing number of bacteria, viruses, and pathogens in the hot tub.
  • Overall, high pH in a hot tub, when unchecked can lead to a whole lot of extra cost. Cost of buying more sanitizing chemicals than usual and cost of repairing or replacing spoilt hot tub hardware as a result of accumulating calcium scales.

So, it is advisable to check your hot tub pH levels regularly and correct them.

How to lower pH in a hot tub?

The ideal recommended pH level for water in a hot tub is somewhere between 7.4 and 7.6. So if your water pH level is reading above this range, it is time to lower it a bit to avoid the effects caused by unbalanced water chemistry.

To lower your hot tub‘s pH, your preferred chemical should be muriatic acid or sodium bisulfate.

Muriatic acid is inexpensive. It is very common, but using it comes with some risks. It can cause serious burns to the skin and eyes. 

Sodium bisulfate, on the other hand, is more expensive than muriatic acid and comes in a more mild dry granular form, making it safer to use.

You can use muriatic acid not just as a cleaning agent for cleaning stains and getting rid of algae and mold, but also to quickly lower your hot tub pH. To use it

  • Test the pH level in your hot tub first before you begin. Only then can you know the current pH and calculate the needed amount of acid to be added to get to the ideal level.
  • Dilute your acid in water. You do not want to turn your hot tub into an acid bath. The proper dosage is usually indicated on the acid container. But just in case, dilute 1 unit of acid in 10 units of water and mix properly.
  • Now add the diluted acid carefully and gradually into your hot tub.
  • Allow it to circulate and mix very well.
  • After a few hours, say 3 to 5 hours, check the pH level again to see if it’s okay. If otherwise, add diluted acid again and test again after a few hours.
  • Continue the process until you get the ideal pH range.
  • Take the necessary precautions when using muriatic acid or any other acid.
  • Always put on protective gear at all times when handling acids.
  • Never add water to acid, if you are diluting, add acid to water instead.

Will baking soda lower pH in a hot tub?

Baking soda, otherwise known as sodium bicarbonate, can be a little confusing when it comes to whether it lowers or increases pH level.  It can lower pH or raise it, depending on the pH level of the solution to which it is being added. 

In solutions where the pH level is lower than that of the baking soda, it acts as a base and raises the pH. If added to a stronger basic solution where the pH level is higher than that of its own, it acts as an acid. Meaning it will increase the pH level in such a situation, though just a slight increase.

So will baking soda lower the pH in a hot tub? The answer is no. Water has a neutral pH level of 7, and even the so-called high pH level of your hot tub will not be too far fetched from this. 

The pH of baking soda is around 8.3. Being higher, it will raise the pH in the hot tub instead of lowering it when added. So if your goal is to lower the pH level in your hot tub, go for something else.

Why is baking soda used when lowering pH?

However, baking soda plays an important role in lowering the pH in a hot tub. In lowering the pH level, the total alkalinity also drops, depending on which pH down is being used. 

Total alkalinity plays a very important role in keeping your pH level in check. Rather than pH spiking up all of a sudden or dropping too low, your TA acts as a buffer, preventing these fluctuations.

A TA of between 80 and 120 ppm is the right measure if you want to keep a stable hot tub chemical level.

In raising the total alkalinity of your hot tub, baking soda and soda ash are serious game players in this aspect as they do just that. But then, between both, baking soda is the most preferred, the reason being that it raises the Total Alkalinity without much effect on the pH. 

You do not want a case wherein a bid to raise the TA, you end up raising the pH above the ideal level again, and the balancing cycle continues.

So after you are done lowering the pH of your hot tub water. Check the TA and add baking soda to increase it.

What is the Difference Between Baking Soda and Soda Ash?

These two chemicals are very much similar, but each is unique from the other. It is important to know the differences to know how best to use them.

Baking soda, known as sodium bicarbonate, with a chemical makeup of NaHCO3, has a pH level circling 8.3. while soda ash, known as sodium carbonate, with a chemical composition of Na2CO3, has a pH ranging from 11.3 to 11.7.

Both comprise Sodium but have different responses when dissolved in water.

Soda ash in water dissolves into an alkaline solution, capable of causing a significant shift in the pH level of whatever medium it is added to.

Baking soda, on the other hand, when dissolved, toggles between being an acid or an alkaline solution.

Can I use vinegar to lower the pH in my hot tub?

Vinegar is acidic and thus can be used to lower the pH in the hot tub. As a popular household cleaning agent, vinegar can also be used to clean your hot tub and, at the same time, adjust your pH. 

It is safe to use in your hot tub, but as a pH adjuster it will not get the job done as Muriatic acid or Sodium Bisulfate, so it is not recommended for use when lowering your hot tub pH.

If you want to use it to clean your hot tub, that is fine, but it should not be your first choice for a hot tub cleaning agent.

If you want to use vinegar in your hot tub, use white vinegar. Other ones might leave color stains on your hot tub walls. You can read further here.

Does chlorine lower pH?

The high amount of chlorine in your hot tub will decrease the pH level. But the downside to this is the health hazard associated with too much exposure to high levels of chlorine.

Exposure can cause, among other things, damage to the skin and eyes, and irritation in the lungs. It can also trigger asthma in patients.

Aside from the health risks, high chlorine levels are bad for your hot tub health.

How do I reduce Chlorine levels in a hot tub?

Since a high chlorine level is not good for your health and that of your hot tub, It’s best to reduce it when you notice it’s high. The surest way of telling if the chlorine levels in your spa are high is by testing for it. 

Not every irritation you experience while soaking is a sign that the chlorine level is high. So if you have tested and your chlorine level is too high, here is how to go about reducing it.

  1. Draining and refilling your hot tub. This is the quickest way, but it’s a bit more expensive as you might have to rebalance your water chemistry.
  2. Refrain from using your hot tub and the chlorine levels will drop naturally on their own. Allowing your hot tub to stay for a day or more without using it or adding any more chemicals will cause the chlorine level to drop faster when it is exposed to sunlight.
  3. Add chlorine neutralizers. When chlorine neutralizers such as sodium thiosulfate are added, they will help balance the chlorine level by neutralizing the excess chlorine.

Whatever way you use it, be sure to test your hot tub again after a while to confirm that the chlorine level is ideal before you proceed to use it.

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