Toiletsguide is audience-supported. When you buy through links on this site, we may earn an affiliate commission that we use for site maintenance. Learn more


Hot Tub Smells like Chemicals – DIY Troubleshooting!

Hot Tub Smells like Chemicals
Written by Kai Michel
Last Update: August 10, 2023

Does your hot tub or spa smell? You may think there’s too much chlorine but that rarely is the case.

Some odors are environmental, some are chemical. But most odors can be treated and cured successfully.

Just don’t try to mask odors with aromatherapy products and spa fragrances. You’ll end up making the situation worse.

Let’s deal with the root causes!

Reasons Behind Chemical Odor Coming from Your Hot Tub

1. pH level

The optimum pH range for a hot tub is between 7.4-7.6. If the pH level goes too up or down the tub will be smelly soon.

You may get a pungent odor from the water if the pH is too low. The smell will be stale if the pH level gets too high.

2. Sanitizer level

The right combination of your water and sanitizer is crucial. The warm and humid environment of your hot tub is a perfect place to grow bacteria and the sanitizer keeps them in check.

If the sanitizer level or type gets messed up, that can cause odor. Follow the instructions on your owner manual and the back of the chemical jar to know how much of what you should use.

3. Biofilm

Biofilms are the “icky slime” that forms on the surface of the water if the pool/tub is left unused for a while. The layer of bacteria has a pungent and heavy smell.

You can use a strong tub rinse to combat this problem. We recommend leaving the tub rinse overnight before you drain the tub.

What Your Hot Tub Smells Like and Why

1. Hot tub smells like rotten eggs

Sulfur dioxide has a distinctive rotten-egg-like smell. If you notice that odor, this means the water has a high level of sulfur bacteria. This is a common problem for bromine users.

This can also happen to you if you leave your tub for a long time (5 or 6 weeks or more). The cure is easy though – just “Shock” the water with chlorine and you’ll be good to go.

2. Hot tub water is cloudy and smelly

If the chemicals don’t get enough time to incorporate with the water, you may get the opposite result of what you are looking for. The water will become cloudy and smelly when you turn on the jets.

This is especially common for newbies that use solids like tablets or crystals instead of powder or liquid.

How to get it fixed? Drain the tub completely and use less amount of chemicals next time.

3. Hot tub smells like ammonia

Chloramines are to blame here. Contradictory to what many people believe, your tub water shouldn’t have any kind of smell.

Excessive chlorine molecules get attached to the ammonia residue from perspiration, oils, or urine, and create chloramines. Shocking the water can help you get the odor out.

4. Hot tub smells like fish

It is unlikely that someone dumped fish in your tub just to piss you off. There can be elements like chloramines, cadmium, or barium in your water that would explain the fishy smell.

Shocking your water with chlorine granules will solve the problem. You also need to drain your rub completely and fish out any residual remnants that have built up.

5. Hot tub smells like plastic

We talked about biofilms above. They are responsible for the heavy and pungent plastic-like smell. If you use bromine as a conditioner or leave the tub unused for a long period of time, this can happen.

There are a couple of remedies e.g. chemical products like bleach, harsh oxidizers, and surfactants. But the best way actually is to regularly shock your tub and maintain good ventilation.

6. Hot tub smells like chlorine or bromine

If your tub water has excess bromine particles or the pH level is too low, the water can send off a “chemical-like” smell. Use a pH increaser to tackle this issue.

You can also try out a chlorine-based sanitizer but don’t use testing strips with bromine because you’ll get the wrong results.

A smart water care monitor also helps.

7. Hot tub smells like mint

Don’t be deceived by the pleasant mint smell. No smell should come out of your tub or its water. The most likely cause may be growth of molds in your tub.

Drain the whole tub and clean it thoroughly before the mold development gets too complicated. Regular shocking and maintaining the pH level will prevent such conditions.

8. Hot tub water smells musty

If there is a musty smell from your hot tub, your tub lacks maintenance. The smell is caused by alkaline development that may lead to mold growth inside the tub.

You can either clean the tub thoroughly after you drain it or use chemical-based cleaners to get rid of all that unpleasant musty smell. Don’t forget to remove the filters beforehand.

Importance of getting rid of the chemical smell?

When added sanitizer kills bacteria, bromamines, and chloramines are produced as normal byproducts. These chemicals can normally irritate your eyes and skin. They can also cause respiratory issues in high concentration.

That’s why It’s really important to shock your tub on a weekly basis. Make sure to properly ventilate the hot tub.

What to Do if Your Hot Tub Smells Like Chemicals?

Tools needed

  • Testing strips
  • pH increaser/decreaser
  • Chemical resistant gloves
  • Chemical-resistant measuring cup
  • Goggles
  • Dichlor sanitizing agent
  • Your phone

Step 1: Test the water

The first step is to test the water. Take a testing strip and drown it in the water for 5-15 seconds. Make sure that other strips don’t get contaminated by the water.

Now compare the colors visible on the test strip with the jar. You’ll be able to check all the essential values with just one strip.

The window we are looking for is:

Name Expected Amount (Parts Per Million)
FCl (Free Chlorine) 2 – 4ppm
Alkaline 120 -150ppm
pH 7.4 – 7.6ppm
Calcium Hardness 175 – 250ppm

You can also use a traditional liquid test kit to check the water. If you don’t have access to any of those, simply take a sample of your tub water and take it to the nearest hot tub experts.

Step 2: Balance the pH and other elements

It’s time to balance the chemicals. Suit up with safety gears and use a pH increaser/decreaser to balance the pH level first. How much you need to use will be mentioned in your user manual.

Turn off the air-jets and leave the circulation pumps on. Apply the chemicals and give it a rest. Don’t cover up the tub. Instead, keep the air circulation free and open.

Step 3: Set a reminder

Each time you use chemicals in your hot tub, the circulation pumps will incorporate the chemicals all over the tub. The process will take time.

We recommend that you create a 15-20 min reminder for each dose of pH balancers. Apply one dose and check the water again in 20 minutes. Repeat the process till you get the desired results.

Step 4: Shock the water

Once the pH level is in the optimum range, it’s time to shock the water.

You can use a dichlor, a biguanide, a mineral, or a non-chlorine shocking agent according to the instruction manual.

We recommend a stable dichlor shock that can tolerate high heat and works well in most tubs. Check the right amount needed from the back of the jar.

If you want to figure out how much water your tub can hold, see the manual or use this equation:

L (Feet) x W (Feet) x D (Feet) x 7.5 = V (Gallons)

Where L = Length
W =Width
D = Depth, and
V = Volume of your tub

Take the shocking agent and spread it over the tub. Keep the circulation pumps on.

Give it around 20-30 minutes and check if all elements come within the range or not.

If not, continue the process till you’re happy with the result.

Step 5: Enjoy your tub!

You can start enjoying a hot refreshing shower on your tub once all the materials are within the ideal range. It’ll take time to adjust all the elements.

Keep applying chemicals until everything is fine.

Usually, 30-60 minutes is the appropriate time to start enjoying your tub again but you are free to use the tub once the FCI count goes down under 5ppm.


1. What are chloramines?

Ans: Chloramines are chlorine-based waste products. The chlorine from the sanitizer reacts with ammonia residues and creates chloramines. They are responsible for water smelling like ammonia.

2. What are bromamines?

Ans: Bromamines are bromine-based waste products and many people use bromine-based sanitizers because they are soft on skins. Bromamines react with ammonia residue and create bromamines. Unlike chloramines, they don’t have a powerful smell and are great sanitizers.

3. What can I use instead of chlorine in a hot tub?

Ans: If your goal is to oxidize the water without disinfecting, a non-chlorine-based agent can help you. They work by creating free chlorine molecules that help to clear cloudy waters. Talk to the professionals if you want to switch.

4. Are hot tubs hot enough to kill bacteria?

Ans: The temperature of a hot tub usually goes no hotter than 104 degrees, which isn’t enough to kill some heat-resistant bacteria. That’s why we recommend using shocking agents and sanitizers.

5. Is it bad to use a hot tub without chemicals?

Ans: There is no way to prevent bacterial or fungus invasion without the help from chemicals. Your tub will probably turn green from all the algae, mold, and fungi growing within a couple of hours. If you have sensitive skin, use bromine-based products instead of chlorine-based ones.

About the author

Kai Michel

Hello, this is Kai, addressing homeowners in need of some help with their home renovation projects. I’ve worked on numerous toilet repair projects over the years that incorporated a wide variety of tasks, from repair to renovation and maintenance. Besides acquiring a degree on the legal codes and procedures, I gathered vast insights into bathroom settings, toilets, showers, fittings, and other household appliances, fixtures, and components. This helps me guide my clients through their home improvement and interior development plans. Since maintenance is my area of expertise, I can assist people in all phases of the actual ‘improvement’ process. To get my messages even further, I contribute to this site through my blog posts. Check my content here for expert suggestions!

Leave a Comment