Why is my Hot Tub Water Green? (And How to Fix it) | Blog

Dealing with green hot tub water can be unsettling and unpleasant, but it's usually a fixable issue. This guide is designed to help you quickly understand why it happens to your hot tub and what you can do to clear up your water, so you can get back to enjoying your relaxing soak.

Why Is Your Hot Tub Water Green?

Algae: The Main Cause

Algae growth is the top reason your hot tub water turns green. These tiny organisms love warm, still water, especially when the water's chemical balance isn't right. If there's not enough sanitiser, like chlorine or bromine, or if the pH level is off, algae can quickly spread. This turns your clear hot tub water into a green, murky mess. Algae not only looks bad but can also make the surfaces slippery and clog your filter, making cleaning harder.

Metals: A Less Common Cause

Sometimes, the green colour in your jacuzzi or hot tub isn't from algae but from metals, like copper. This is less common and can happen if you fill your hot tub with well water or if there's corrosion in the hot tub's metal parts. When these metals mix with the water and air, they can turn the water green. Unlike algae, this kind of green water isn't about cleanliness but shows there's a chemical balance issue that needs fixing.

Step-by-Step Guide to Clear Green Water

1. Test and Adjust Chemical Levels

Start by checking your hot tub's chemical balance. Grab a water testing kit and measure the levels of sanitiser (like chlorine or bromine) and the pH. You'll want your sanitiser levels to be in the right range (1-3 ppm for chlorine, 3-5 ppm for bromine) and the pH to be between 7.2 and 7.6. If anything's off, follow the instructions on your chemical products to get everything back to where it should be.

2. Shock Your Hot Tub

After getting your chemical levels sorted, the next move is to shock your hot tub. This means adding a big dose of sanitiser to zap all the algae, bacteria, and other yucky stuff. Check the instructions on your shock treatment for how much to use. Remember to leave the jacuzzi cover off for a bit (at least 20 minutes) after you shock it to let things air out.

3. Clean or Replace the Filter

A clean filter is key to clear water. If your hot tub spa water is green, it's likely your filter is clogged up with algae and debris. Take it out and clean it as per the manufacturer's guide. If your filter's seen better days (old or damaged), it's time for a new one. A fresh, clean filter helps keep your water looking good and algae-free.

4. Drain and Clean the Tub (If Necessary)

If your water is still green after you've done all the above, you might need to drain and give your hot tub jacuzzi a deep clean. Empty out the water following the maker's instructions. Clean the tub with a gentle cleaner meant for hot tubs, especially targeting any slimy spots. Those slimy areas are signs of algae. Once cleaned, rinse well, fill it back up with fresh water, and balance your chemicals. This should give you a fresh start for clear, clean water.

How to Prevent Green Water

Regular Maintenance Tips

Preventing green water is all about sticking to a regular maintenance routine, which you can learn more about in our beginner’s guide to hot tub maintenance. Here's how to keep your hot tub in top shape:


  • Weekly Water Testing: Regularly check and adjust your hot tub's chemical levels. This includes making sure your sanitiser (chlorine or bromine) is within the effective range and the pH is balanced between 7.2 and 7.6.
  • Hot Tub Cover Care: Keep your cover clean and in good condition. A dirty cover can introduce contaminants into the water, so cleaning it helps prevent issues.
  • Filter Maintenance: Clean your hot tub filter monthly, or more often if you use your hot tub frequently. A clean filter is crucial for maintaining clear water and preventing algae growth.
  • Use a Cover: Always put the cover on your hot tub spa when it's not in use to keep out debris, leaves, and other potential contaminants.


If carrying out a consistent maintenance routine sounds like too much of a chore, consider our self-cleaning swim spas, where the hot tub automates most of its own upkeep for you.

Chemical Balance and Filtration

Maintaining the right chemical balance and ensuring your filtration system is working efficiently are key steps in preventing algae growth:


  • Sanitiser Levels: Keep an eye on your sanitiser levels, adjusting as needed to ensure they're always within the recommended range. This helps kill off any algae spores before they can grow.
  • Filtration System: Ensure your hot tub's filtration system runs for at least 4-6 hours daily. This keeps the water moving and filters out any impurities, which is essential for preventing algae and keeping the water clear.


Green hot tub water can be a nuisance, but with the right knowledge and a bit of effort, it's a solvable problem. By understanding the causes, taking prompt action to treat the water, and following through with regular maintenance, you can keep your hot tub inviting, clean, and ready for relaxation. Enjoy the peace of mind and comfort that comes with a well-maintained hot tub.


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How do I Clear the Green Water in my Hot Tub?

Clearing green water from your hot tub involves a few key steps:


Test and Adjust Chemical Levels: Use a water testing kit to check the sanitiser and pH levels. Adjust these levels as needed to ensure they're within the ideal range.

Shock Your Hot Tub: Apply a shock treatment to the water to kill algae and other organic contaminants. Follow the instructions on the shock product for the correct dosage.

Clean or Replace the Filter: Inspect the filter for debris and clogs. Clean it thoroughly or replace it if it's damaged or excessively dirty.

Drain and Clean the Tub (If Necessary): If the green water persists, you may need to drain the hot tub, clean it thoroughly, and refill it with fresh water.

Is it Safe to go in Green Hot Tub Water?

It's not recommended to go into green hot tub water. Green water indicates the presence of algae and possibly other contaminants like bacteria, which can pose health risks, including skin irritation and infections. Always clear the water and ensure it's properly sanitised before using your hot tub.

Will shocking a Hot Tub Get Rid of Green Water?

Yes, shocking your hot tub can effectively get rid of green water, as it involves adding a large dose of sanitiser to the water to kill algae and other organic matter. However, for the best results, shocking should be part of a comprehensive approach that includes testing and adjusting chemical levels, cleaning or replacing the filter, and possibly draining and cleaning the tub if the problem persists.