Are Hot Tubs Hygienic? How To Tell if a Spa Is Dirty

Jennifer Rhodes

By Jennifer Rhodes · Updated

As an Amazon Associate I earn from qualifying purchases.

Hot tubs can be a great source of relaxation and enjoyment, but it's important to consider their hygiene as well. While properly maintained hot tubs can be perfectly safe and hygienic, many hot tubs—especially public ones—are frequently not as clean and free of bacteria as you would like.

Common bacteria found in hot tubs can cause infections such as folliculitis, hot tub rash, and Legionnaires' disease. To minimize the risk of bacteria growth, it's essential that hot tubs are properly maintained.

In this post, I’ll talk about the risks of using a dirty hot tub, as well as what it takes to keep a hot tub clean. But first, I want to offer some tips you can use to tell if a hot tub is likely to be clean or not BEFORE you get in.

How to tell if a hot tub is clean

Many of us have been in this situation: you're at a pool, ski resort, vacation rental, or even a friend's house... and there's a hot tub. Getting in for a soak seems tempting, but you have no way of knowing if the water has been properly maintained. How can you be sure it's clean?

The only real way to know is to test the water, but that requires knowing how to use test strips and read the results. If you want to do this, my quick maintenance guide has the values you need, and you can pick up some test strips to take with you quite cheaply:

Poolmaster 22211 Smart 4-Way Swimming Pool and Spa Water Chemistry Test Strips
Poolmaster 22211 Smart 4-Way Swimming Pool and Spa Water Chemistry Test Strips
View on Amazon

If you don't have access to test strips, don't worry. There are still a few warning signs you can look out for when trying to figure out if a hot tub is safe to bathe in:

1. Cloudy or discolored water

Hot tub water should be clear, possibly with a slight blue tint if the shell is white or silver. If you notice any milky or cloudy look to the water, that could indicate an unsanitary spa.

2. Foul or chemical odors

Distinctive odors in a hot tub can be a sign of a number of problems, including improper water balance, pH levels, and sanitizer. A properly balanced hot tub should smell of almost nothing.

A strong chemical scent in a hot tub usually means a hot tub actually has too little chlorine or bromine—not too much.

If there's any hint of pond, fish, or mildew, you might want to skip this one.

3. Unusual residue or scum on the surface of the water

Hot tub water should be clean and clear, without anything floating around on the surface. If you see brown, green, or slimy substances floating around or sticking to the sides around the waterline, it's probably bacteria.

4. Excessive foam or bubbles

When the jets are on, every spa will produce bubbles as the water is stirred up. But this 'foam' shouldn't linger for long once the jets are off. If it does, it's probably a sign of a sanitation problem.

5. Visible mold or mildew

This one might be obvious, but if you can see any black, green or brown mold growing inside a hot tub, that's a bad sign. If it's bad enough that it's growing in the visible areas, just think about what's going on down there in all those pipes you can't see.

6. Waterline stains

When scum is allowed to accumulate on the water's surface for long enough, it can start to form a stain around the waterline. This may or may not be directly harmful, but it's still a sign of a spa that has not been maintained in great condition.

Risks and precautions

There are a few reasons you probably want to avoid using a dirty or poorly-maintained hot tub:

  1. Skin irritation: Dirty hot tubs can contain bacteria and other microorganisms, which can cause skin irritation, rashes and other uncomfortable reactions.
  2. Infections: While many bacteria are not directly harmful to humans, hot tubs can also contain harmful bacteria and other microorganisms, which can lead to infections, including Legionnaires' disease.
  3. Chemical Imbalances: In addition to skin problems, poorly-maintained hot tubs can also have chemical imbalances which can cause a variety of respiratory issues and other health problems.
  4. Eye Irritation: Another common problem is eye irritation, as the water can contain contaminants that are released in the steam coming off the water's surface, which can irritate the eyes.
  5. Unsanitary Conditions: Even if you don't suffer any ill effects, there's also just the gross factor—nobody likes the thought of sitting in a warm tub of bacteria.

If you ever have any doubt about the cleanliness of a hot tub (using the warning signs above as a guide) the only sure-fire way to avoid the risk of anything nasty happening is to not get in.

If you do have control of the hot tub though, it's not too hard to keep a clean spa once you've established proper hygiene and a regular maintenance routine.

Hot tub maintenance and hygiene

Regular cleaning and maintenance of a hot tub is essential to keeping it functioning properly and ensuring that the water is safe to bathe in. And luckily, it can also help you avoid all of the problems outlined above.

Balancing hot tub water (and especially maintaining the correct levels of sanitizer) will help to prevent the build-up of bacteria, algae, and other contaminants which can cause health issues. It will also help to keep the water clear and free from any unpleasant odors.

The role of sanitizer in a hot tub

Sanitizer (usually chlorine or bromine) is essential to keeping hot tubs clean. Correct levels of sanitizer will kill bacteria and other organisms, preventing them from growing in the hot tub water. Sanitizer works to oxidize organic contaminants, breaking them down so they can be filtered out or killed.

Without sanitizer, hot tubs are very prone to bacteria and algae growth, and other contaminants which can make the hot tub unsafe to use. Sanitizing a hot tub regularly with the appropriate amount of sanitizer is necessary to keep any hot tub water clean and safe.

Correct maintenance can also help to prolong the life of your hot tub by ensuring that all of the components stay functioning properly, free from corrosion. And of course, it will keep the tub looking nice and ensure that your guests have a pleasant experience when using it.

I have a free printable hot tub maintenance schedule which you can download to remind you of exactly what to do.


Given the right conditions, bacteria will grow. And unfortunately, hot tubs provide the perfect environment: warm, moist and dark. Combine this with the fact that hot tub water is constantly exposed to contaminants from sweat and other body fluids, and without the right maintenance, you quickly have a problem on your hands.

Luckily there are several telltale signs you can use to get a rough idea of if a hot tub is clean—even if you don't have any test strips to hand. If in doubt about the cleanliness of a hot tub, it's safest not to use it, or you risk exposing yourself to a range of potential health issues.

Stay in touch

Get exclusive tips on how to make the most of your hot tub.

We won't spam you. Unsubscribe any time.