How To Lower pH In Your Hot Tub (When It Gets Too High)



pH is the measure of how acidic or basic (alkaline) your water is.

Like a swimming pool, the ideal pH level for your hut tub is between 7.4 and 7.6. Anything above this range will eventually lead to issues with your hot tub chemistry.

Let’s talk about what causes rising pH, why it’s important to keep an eye on it, and how to correctly lower pH in your hot tub.

Why Your Tub Has High pH

When a hot tub’s pH level starts to creep higher than 7.6, the water becomes alkaline, or basic. Due to the tub’s smaller body of water, this problem can arise quickly if the water isn’t regularly monitored.

High pH can be caused by a number of issues.

The first thing you should look at is the tub’s TA level. When it’s high, the pH usually is as well. 

Shocking the water will also cause a pH spike, as it breaks up combined chlorine (chloramines) while increasing free chlorine.

Most homeowners use their main water sources to fill the tub. Depending on where the water comes from, it could have a high pH level to begin with.

Another reason could be that you’ve simply added too much pH Increaser when you were raising the pH level of the tub.

Why High pH Is Bad News

If the water has a high pH level, you need to deal with it ASAP. If you don’t, you can expect any of the following issues to occur:

  • Cloudy tub. Healthy hot tub water is crystal clear and inviting. A tub with a high pH level will have significantly cloudy water. The reason for this is due to the high pH affecting how the chemicals interact with each other. It will cause the water to improperly dissolve calcium, which gives it a hazy look.
  • Chlorine demand goes up. A high pH tub requires more chlorine to keep the water free of bacteria, viruses, and pathogens. This means you’ll have to top up the water more often, and you’ll also be spending more money on sanitizer.
  • Scale buildup. Scale is a nasty build up that floats on the surface of the water. It can also be present on the tub’s walls and even in the plumbing. This occurs in high pH tubs because the high calcium level in the water combines with carbon dioxide to create calcium carbonate.
  • Equipment issues. With water issues comes the risk of equipment issues. The high pH can damage your pipes, pump, and filter if left unchecked. In many cases, replacing these damaged items is the only way to restore them.
  • Itchy bathing. Another side effect of high pH is that the water becomes an irritant to bathers. Things like itchy eyes and skin are common, and nasal passages can become irritated as well. For some people, this water can cause respiratory distress.  

How To Lower pH In A Hot Tub

You won’t have to live with any of those problems if you lower the pH level. Here are a few methods you can use.

Method #1: Use Muriatic Acid

Muriatic acid is the most common chemical used to lower the water’s pH, and it’s usually due to the cost, as it’s relatively inexpensive.

However, that doesn’t mean this acid doesn’t come with some risk. 

Muriatic acid is available in dry or liquid forms, and is an extremely corrosive chemical. It’s important you feel comfortable handling an acid of this nature, as it can cause skin burns, eye damage, as well as nose and lung irritation.

Nevertheless, it lowers the pH quickly and can even be used to clean stains, kill mold and algae, and dissolve calcium build up in the tub.

Here’s how to add it to your hot tub:

  1. Start by testing your hot tub to find out the current pH level of the water. You can do this with either test strips, a liquid test kit, or a digital tester.
  2. Determine the amount of acid you will need to add to the water to raise it so it’s between 7.4 and 7.6. Consult the instructions on the bottle for the proper dosage.
  3. Put on your protective gear. This means chemically resistant gloves, safety goggles, a chemical mask, and wearing long sleeves and pants so it won’t burn your skin if accidently splashed.
  4. Dilute 1 part acid into 10 parts of water (never the other way around). Mix up the solution in a large bucket using a wooden stir stick.
  5. Carefully pour the solution into the tub and let it circulate for a few hours.
  6. Retest the water and adjust the pH level if necessary.

Method #2: Use Sodium Bisulfate (Dry Acid)

More safe to use than muriatic acid, but also more expensive, is sodium bisulfate. This dry acid is milder and available in granular form.

It does a good job lowering the tub’s pH level, but you should still exercise a degree of caution when using it. After all, acid is acid, and you don’t want to get sodium bisulfate granules in your eye on a windy day!

Here’s how to add it to your hot tub:

  1. Test the hot tub water using test strips, a liquid test kit, or a digital tester. Record the current pH level of the water.
  2. Consult the instructions on the bottle and calculate the proper dosage you’ll require to raise the tub to anywhere between 7.4 and 7.6. 
  3. Time to suit up! Use chemically-resistant gloves as well as safety goggles to protect your eyes when handling this acid.
  4. Fill a large bucket with water and pour in the measured granules. Mix up the granules until they’re fully dissolved using a wooden stir stick. Make sure they are all dissolved so they don’t damage the hot tub’s shell.
  5. Dump the solution into the tub and let it circulate for anywhere from 3 to 5 hours.
  6. Retest the water and adjust the pH level if necessary.

How To Bring Total Alkalinity Back Up

After lowering the hot tub’s pH level, you may end up with a low TA level as well. Raising this can be done using either baking soda or soda ash

Baking soda is the preferred method that most hot tub owners use. This is because it works well at raising the TA, and minimally affects the pH level. 

Soda ash, on the other hand, will have a dramatic effect on the water’s alkalinity, but will also raise the pH level of the water in the process.

Pick Your Poison!

The only way to lower alkalinity in your hot tub is by using an acid. 

Both muriatic acid and sodium bisulfate will do the job, and it’s up to you to weigh the pros and cons of each.

Categories: Hot Tub Care, Hot Tub Chemistry