hot tub smells like fish

No one in their right mind wants to relax in a smelly hot tub.

Whether it smells like a moldy mess or a wet dog, it’s up to you to play detective and find the cause of the scent in order to keep yourself and your equipment safe during future use. Of course, you might be thinking,

“How in the world do I figure out where that smell is coming from?”

Luckily, you’ve come to the right place.

Come dive in with us as we explain the proper action to take when your hot tub water smells bad.

How To Make A Hot Tub Smell Better

There are a few major culprits you’ll want to look into if your hot tub water smells bad, though one of the primary reasons hot tub owners deal with foul scents is hot tub water.

Let’s see what we can do to bring our hot tub water back to life.

How To Make Hot Tub Water Smell Good

One of the first things to check when you get a foul odor is the water chemistry.

Hot tubs are humid, moist, and warm. This is the ideal breeding ground for unwanted bacteria.

To avoid bacteria growth, you must keep your water clean and your chemistry balanced. Not only will this get rid of any bad smell, but it will also keep you and anyone who uses your hot tub safe.

The culprit is likely
low pH if you’re getting a sharp, pungent smell from your spa water. 

However, if you get a stale, musty scent from your spa water, it is likely high pH. See our “What Causes High pH In A Hot Tub” article for solutions to bring your pH back down to an acceptable level. 

The ideal pH range for hot tubs is between 7.4 and 7.7.

Shock Your Spa

The first thing you’ll want to do when getting rid of your hot tub odor is shock your spa.

Essentially, you’re bringing in an additional dose of sanitizer to annihilate bacteria. Using granular chlorine, you will bring your spa’s chlorine level up to a fairly high level (somewhere around 100ppm). If you’re using chlorine granules, we recommend dissolving them beforehand in a large container, so the rough edges of the granules don’t scratch your tub’s surface.

Once you’ve added the chlorine, put your spa cover on, turn your hot tub to high speed, and circulate the water for at least 30 minutes. Make sure all of the jets are running to maximize water circulation.

Get Rid of Gases

Once you’ve shocked your spa, we recommend leaving the cover off for at least a few hours. This allows chemical gases to escape. Also, make sure there isn’t any rain or wind that day, as debris could end up blowing into the freshwater that you just took so much time to adjust.

Test Your Water

To check the chlorine levels in your spa, you must use test strips or a test kit. You’ll know if the decontamination process was successful if you end up getting a free chlorine reading. However, if you test your water and don’t get a chlorine reading, you might have to go through the process again.

Check Your Hot Tub Cover

While your spa cover is there to protect your tub from debris and other bacteria, there are times when it becomes the source of foul scents.

Waterlogged hot tub covers are the product of age or low-quality. When this happens, they become the ideal breeding ground for mold and bacteria.

Most manufacturers design spa covers to drain so that water doesn’t pool. However, after so many years, any cover will lose its integrity. Freshwater that sits in a warm, dark environment for so long will eventually turn into a smelly mess.

If you’ve been using your spa cover for five years or more, you might just need to replace it. Don’t worry. This is totally normal. Covers don’t ever last forever.

Visit The Cover Guy Reviews to see some of the highest rated hot tub covers if you’re in the market for a new one.

However, if your cover isn’t ancient and you think it might be the source of the foul odor, start by removing it from the top of your spa and over to an area where you can clean it.

Start by unzipping the cover’s openings and taking the foam inserts out to allow them to dry. If you see any dust, debris, or mildew growing atop your cover, use a brush or broom to get rid of it.

Using a damp cloth and an eco-friendly cleaning solution, wipe your cover down. There are cleaning solutions made specifically for spas, which you can typically find at your local pool store.

Allow your cover components to dry completely before you put everything back together.

Check The Plumbing

While hot tub covers and water are the two most common culprits, there are times when the internal components are the root of the problem. Although this job can be a bit more challenging to deal with, it’s not impossible.

If you haven’t been cleaning your system properly, or you’ve left water sitting in the pipes while the rest of your tub is empty, you may have bacteria buildup on your filter and plumbing components.

Pesky bio-film will sometimes enter your plumbing system. For example, hot tub owners often see green or brown remnants of bio-film on their hot tub filter.

In this case, you might have to pull a full reset on your water chemistry and completely purge your system. After shocking your water, use a chemical like Spa Purge to clean out contaminants such as mold and bacteria inside your filter, pipes, jets, and plumbing.

Once you’ve purged your water, empty the water and refill it. Make sure to add chemicals and test the pH levels and alkalinity levels to keep your spa balanced.

If your water testing shows that some adjustments need to be made, our article on How To Raise & Lower Alkalinity In A Hot Tub can help you do just that!  

If you notice a bromine odor in your hot tub, the first thing to do is wait it out.

Remove the cover from the top of your spa and allow it to breathe. Over time, the sanitizer will break down and release into the air.

Though this process could take a day or two, the odor may fade away completely. If it does not fade, you might have to dilute the water and lower your sanitizer levels.

Using a five-gallon bucket, remove some of your hot tub’s water. 

 In some cases, you may need to remove half of the water in your spa for this to work. Once removed, use fresh water to replace the water you just took out.

After you fill it, run the jets and allow the water to circulate. If the odor doesn’t disappear, you may need to drain the water completely and reset your sanitizer levels.

Lastly, if your sanitizer levels are far too high, it is a good idea to use a neutralizer. We only recommend doing this if you’re planning on using your spa right away. Otherwise, it’s best to let those chemicals break down naturally. The best neutralizer out there is sodium thiosulfate, which lowers chemical levels and allows you to enjoy your spa sooner.

Why Does My Hot Tub Smell Like Fish

If your spa smells like fish, it’s an excellent idea to hyper-chlorinate it, which will eliminate excess bacteria. To do this, you can use spa shock chemicals to drastically raise the chlorine level in your spa, killing any algae, mold, and foul-smelling bacteria.  Check out Best Hot Tub Chemicals and Best Hot Tub Chemicals For Sensitive Skin for our favorite products.

Why Does My Hot Tub Smell Like Rotten Eggs

The scent of rotten eggs is common in spa water that contains excess sulfur bacteria, which typically appear within the filtration system. This bacteria will usually form Hydrogen Sulfide when it reacts to warm temperatures, giving you that expired egg scent.

Final Thoughts – Avoiding Smells In The Future

One of the best ways to avoid any nasty smells later down the line is by performing routine maintenance on your spa. By cleaning your tub regularly and ensuring the chemical levels are balanced, you can avoid these types of issues altogether.

If you ever notice an unpleasant scent coming from your hot tub, make sure to follow the steps above to determine the source and get rid of it.

As always, keep your pH level within the proper range and maintain high enough chemical levels to kill any smelly bacteria or other substances.

Be sure to read out Hot Tub Maintenance guide to learn how to properly clean your spa, as keeping a routine cleaning schedule will avert any future smells from arising during your spa ownership.

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