Can You Use a Hot Tub if the pH is High?

I love to use my hot tub after a long hard day. But sometimes it’s tricky getting the chemicals balanced and I’ve wondered can you use a hot tub if the pH is high?

Here’s what I discovered after looking into it:

You should NOT use your hot tub if the pH is too high (above 7.8). That can lead to itchy skin and burning eyes. But it can also cause scale build-up which can clog pipes and shorten equipment lifespans. If the total alkalinity is off, that can make it hard to balance pH. So start by ensuring proper alkalinity.

But there’s more to know about pH, safe water chemistry and what the pH should be. So in this article, we’re diving deep into pH, water chemistry in general and when it’s no longer safe to use your hot tub.

Let’s dive in! (pun intended)

What is pH as it relates to hot tubs?

Technically, as every chemistry student knows, pH measures any water-based solution on a scale for how acidic it is.

Totally neutral water, at room temperature, has  pH of 7.0. Despite what you might think, highly acidic water has a low pH, whereas highly alkaline water has a high pH.

In a hot tub, we measure both pH and alkalinity.

pH and alkalinity, while similar, are altogether different. Alkalinity is a measure of the ability of the water to neutralize acidity, whereas pH simply measures just how acidic the water is.

The 2 can definitely be confusing which is why I wrote a recent article which breaks down the key differences between the 2.

What’s really surprising is the fact that some products we buy are designed to raise or lower both pH and alkalinity, but there’s only 1 thing you can do to raise the pH without affecting alkalinity. Just click the link to see that post on my site.

What happens if pH is too high in hot tub?


A high pH is a bad thing for hot tubs. By high, I mean over 7.8 on those test strips you have.

For starters, it can cause something called scale. If you have ever seen a white, chalky buildup on the surface of the tub just above the waterline or on headrests, that is scale.

But it can also build up in the pipes and equipment. So sometimes you see chalky flakes come out when you turn the jets on.

Eventually, over time, scale can build up in the pipes and equipment and restrict the water flow. The blockage can not only slow down the pressure in your jets but can cause the heater and pump to fail prematurely.

But a high pH can also cause you to go through more bromine or chlorine than you otherwise would need, so it affects your wallet too. Even with lots of sanitizer, a high pH can also keep your water cloudy.

The worst aspect for hot tub users in a hot tub with a high pH, however, is that it can cause burning eyes. The effects are very similar to swimming in a heavily chlorinated pool. It can also cause itchy skin.

So while using a hot tub when the pH is over 7.8 may not be super hazardous to your health, it will likely be uncomfortable. So always check and maintain good water chemistry in your hot tub. That way you get years of fun and comfortable use.

Why is my hot tub pH always high?

A persistently high pH often means your total alkalinity is off.

If your total alkalinity isn’t in the correct range, it makes the pH far more likely to fluctuate or bounce around too high or too low. The ideal range of alkalinity in your hot tub, as expressed in parts per million, is 80-120 ppm.

So if you are struggling to balance your pH, start by fixing your alkalinity.

Often times the products that raise or lower both pH and alkalinity can fix your issue. However, if you need to raise the pH in my pool but not the alkalinity, the best product for that is Magnesium Oxide powder (click to see the best one on Amazon Prime).

If you’re struggling to get the water balanced correctly in your hot tub, or if you’ve gotten the dreaded hot tub rash, definitely take a moment to check out a recent article I wrote where I break everything down about perfect water chemistry.

I was most surprised by what the #1 thing you can add to a hot tub that can cause the most damage (and it’s likely in your house right now).

What should the pH of a hot tub be?

As I mentioned, the range for acceptable pH in a hot tub is a range of between 7.2 and 7.8, and 7.6 is really the optimum.

When the pH is either too high or too low, that’s when some of the most common problems with hot tub water chemistry start to happen.

Check out this handy chart to see some of the most common problems.

Too High a pH Too Low a pH
Low Chlorine/Bromine Effectiveness Low Chlorine/Bromine Effectiveness
Cloudy or Smelly Water Corroded Pipes and Equipment
Scale Build-up Skin and Eye Irritation
Skin and Eye Irritations Poor Alkalinity

So start by adjusting the alkalinity with alkalinity increaser or decreaser.

Then, set about adjusting the pH once alkalinity is set. It can be very hard to balance pH if your alkalinity is off.

Will baking soda lower pH?

No is the short answer. Baking soda works best to increase the alkalinity in your hot tub. So it’s not what you want to lower pH.

Almost all alkalinity increasers are made of sodium bicarbonate (yes, normal baking soda like you have in your pantry). That’s compared to pH increaser, which is sodium carbonate, sometimes called soda ash.

The best product to lower pH in your hot tub is SpaChoice pH Decreaser (click to check the current price on Amazon). I like that product better than some of the ones that just say “spa up” or “spa down” which tend to affect both alkalinity and pH.

Do be careful to not lower your pH too far.

When your pH is low, the water is more acidic. When the water is super-acidic, like a super-high pH, the bromine or chlorine you use to sanitize your water can lose up to 80% of its effectiveness.

When that happens, you might get the right reading on your test strip, but the sanitizer’s ability to fight viruses and bacteria is greatly reduced. If you’ve ever had a rash after using the hot tub, that’s officially called hot tub folliculitis. But most people just call it “hot tub rash”.

So balancing your water before using is the key. But if you need to lower the pH in your hot tub, avoid adding baking soda.

Did I cover everything you wanted to know about whether it’s safe to use a hot tub when the pH is too high?

In this article, we took a look at the pH of hot tubs and how high is too high.

We examined what happens when the pH gets too high, and what to do when it does. We also looked at the urban myth of whether baking soda can lower the pH.

Specifically, though, we answered the question of can you use a hot tub if the pH is high? The answer to that question is, of course, it depends on how high the pH is.

But if the pH is over 7.8 on your test strip, it’s best to NOT use it until you’ve balanced the water chemistry.


Photo credit:

Iguana by the hot tub by John Frazier is licensed under CC2.0

Jeff Campbell

Jeff Campbell is a husband, father, martial artist, budget-master, Disney-addict, musician, hot tub lover, and recovering foodie having spent over 2 decades as a leader for Whole Foods Market.

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