Can You Use a Hot Tub With Low pH? (Know the Safety Risks)


Maintaining the right pH levels inside your hot tub can quickly become an exhausting task. This has no doubt left you wondering if it’s really unsafe to use your hot tub when the pH is low.

Never use a hot tub if the pH is too low. Water pH lower than 7.2 is too acidic for safe bathing. Sanitizers cannot work properly in low pH water, resulting in a build-up of harmful bacteria that causes irritation to your face and skin. Over time, acidic water will corrode any metal parts and crack the hot tub shell.

After we’ve taken a closer look at the dangers of using a hot tub with low pH, we’ll look at what causes the issue in the first place, and why low pH can be the sign of a bigger problem.

What happens if the pH level is too low in a hot tub?

Proper water chemistry ensures that your hot tub is clean, safe to use, and running correctly. In order for the chemicals to work properly, the pH must be within 7.2 and 7.8. For the absolute perfect conditions, try to get a pH of between 7.4 and 7.6.

When the pH is too low, the water becomes acidic, which can cause the following issues:

  • Skin irritation
  • Eye, nose, and throat irritation
  • Corrosion and component damage to your hot tub
  • Sanitizer chemicals become less effective

Low pH effects on your body

If you use a hot tub with low pH, you’ll be left with itchy and dry skin as acidic water strips skin of its natural oils. You’ll also notice irritation in your eyes, nose, and throat when soaking in water with a low pH.

Although it’s not as important as the effects on your body, it’s worth mentioning that the acidic water can break down your swimwear too.

When the water in your hot tub is too acidic, it makes it increasingly difficult for the sanitizers to work effectively. This can leave you exposed to potentially harmful contaminants and increases your chances of being exposed to bacteria such as Pseudomonas aeruginosa (hot tub folliculitis) or legionella, the cause of Legionnaires’ disease.

Contaminated water can leave you feeling unwell and lead to a variety of illnesses through the build-up of bacteria. If you were to use your hot tub with a low pH on a regular basis, you may experience gastrointestinal upsets, stomach cramps, diarrhea, nausea, or vomiting.

While these upsets are mostly short-term, they’ll definitely put a damper on time relaxing in your hot tub.

Low pH effects on your hot tub

If the water in your hot tub is too acidic even for a short amount of time, it can cause no end of problems that will be very costly to repair.

The acidic in low pH water will etch, corrode, or stain any metal parts of your hot tub such as the heater element.

When the pH is low, it reduces your ability to control the total alkalinity of your hot tub water. There’s a lot of confusion surrounding the difference between pH and alkalinity, which will be discussed in the following subheading.

Low total alkalinity caused by the low pH will also damage your hot tub’s surface and components such as the water pump, pipes, and filters.

The surface of your hot tub shell can become etched, pitted, and the acidic water can even crack or delaminate the protective shell layer.

Low pH causes extra running costs

One issue you probably wouldn’t have thought of is the effect on your pocket. Keeping your hot tub sanitizer levels within the correct range is a tricky task if the pH is too low.

Low pH water causes rapid dissipation of hot tub sanitizer. You will end up using a lot more bromine or chlorine than you would otherwise need if your hot tub water were in the appropriate pH range, creating unnecessary expense.

And even if you use lots of sanitizer in low pH water, it still might not be enough to get rid of the unsightly problem of cloudy water. If the sanitizer isn’t working properly, it becomes the perfect environment for harmful bacteria that causes ammonia and algae.

Why is the pH in my hot tub low?

There are several reasons why the pH in your hot tub has become too low. These include:

  • Water has become unbalanced from chemicals
  • Acidic human skin
  • Water source is naturally more acidic
  • Accidental introduction of outside contaminants
  • Total alkalinity is out of balance

Too much pH reducer

One very common reason that the pH level is too low is simply because of adding too much pH reducerOpens in a new tab..

Getting your water just right is a real balancing act. If you’ve overdone it with the reducer, you’ll need to add pH increaserOpens in a new tab. and take a look at the total alkalinity levels.

Acidic human skin

The frequency with which you use your hot tub combined with the number of users has a real impact on the pH levels in your water.

Human skin is fairly acidic (pH 5.5) so that it can ward off harmful bacteria and fungi. Unfortunately, this means that we lower the pH of the water every time we use it.

The problem is worsened further by sweating and the natural oils on our skin. Any lotions or sunscreen that you have applied to your skin will also be washed off inside your warm hot tub water, adding to its acidity.

All of these factors demonstrate why it’s so important to check the condition of the water inside your hot tub frequently.

Water source

If you live in an area of the country that has particularly soft water or you draw your water from a well, then this will naturally lower the pH levels.

Soft water is has a naturally lower mineral count, meaning that it is more acidic than hard water. To address this issue, you’ll need to raise the hardness by adding a calcium hardness increaser such as calcium chloride.

Other contaminants

Grass, dust, and even insects that inevitably find their way into your hot tub water can also can the pH levels to drop.

This is just one of the many benefits of investing in a hot tub cover – the savings made from having a cover really means that it pays for itself over time.

To keep these contaminants to a minimum, it’s a good idea to give yourself a rinse-off before you get into the hot tub if you can. More realistically, make sure to always use clean outdoor footwear that’s reserved only for the times you use your hot tub.

Low alkalinity causes low pH

The difference between pH and alkalinity is one of the most common areas of confusion amongst hot tub users. The confusion arises because of the similarity between the words alkaline and alkalinity.

Failure to understand the difference will have you going round in circles trying to get your water into a safe pH range.

Total alkalinity (TA) is the measure of all the alkaline chemicals dissolved in your hot tub water. Alkaloids such as carbonates, bicarbonates, and hydroxides all contribute toward the concentration levels referred to as the water’s total alkalinity. These concentrations are measured in parts per million (ppm) or milligrams per liter (mg/L).

By contrast, a water’s pH reading is measured along a scale from 1 to 14. 1 is the most acidic, 14 is the most alkaline, and 7 is neutral. This means that a solution is alkaline when it has a pH of 7.1 or higher.

Alkalinity refers to a solution’s ability to neutralize an acid. If the TA level is too low, it will drive the pH level in the hot tub down, turning the hot tub water more acidic.

Because the alkalinity levels in your hot tub work to neutralize the acid (when the water pH is 6.9 or lower), it’s important to address TA levels before adjusting the pH.

Adjust the TA levels in your hot tub by adding alkalinity increaserOpens in a new tab. to achieve a reading of 80 and 120 parts per million. Now that you’ve got the perfect TA levels, you can move on to adjusting the pH to the required range of 7.2 to 7.8.

Constantly chasing pH levels is sign of a bigger problem

Generally speaking, once the pH levels have been set to the safe range of 7.2 to 7.8, you shouldn’t be seeing huge fluctuations either up or down.

If you’ve found that you’re constantly having to chase around trying to get the optimum pH levels, then the easiest option is to drain all of the water and start over afresh.

The day before you drain the water, you should add some line flush and run the hot tub to clean out the plumbing, which will ensure that whatever’s causing the fluctuations is completely removed. Make sure to also give the interior of your hot tub a thorough clean after you’ve drained the water.

Increasing in popularity are water conditioning systems such as Silk BalanceOpens in a new tab.. Once you’ve got the pH and TA levels in the optimum range, the system ensures that these levels are locked in and stay set for four months.

With Silk Balance, you’ll spend less time fiddling with the water chemistry and have peace of mind knowing that there’ll be no nasty surprises to both you and your hot tub.

Did I cover everything?

I always try to provide the most relevant and up-to-date information I can in all of my articles. Saying that, feel free to shoot me an email using the contact form if you think this article is lacking in some way, or if you’ve been left with any doubts.

Thanks for reading and happy hot-tubbing!

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