Hot tub water green

The Best Ways to Fix Green Water in Hot Tubs

When it comes to a relaxing soak in your hot tub, there’s nothing more frustrating than discovering that the crystal-clear water has taken on an unpleasant green color. The good news is you’re not alone; this happens to many hot tub owners. But don’t worry, in this article, we will tell you why hot tub water turns green, whether it is dangerous for you, and most importantly, how to fix the problem of green hot tub water and even prevent it. 

To keep your hot tub water clear, you need the right chemicals. But with so many choices in stores, it’s hard to know what to pick. Check our article about hot tub chemical kits, you will find the answer!

Why Does Hot Tub Water Turn Green?

Water Turn Green

Green hot tub water is a familiar problem for many hot tub owners. You may have experienced disappointment when you uncover your hot tub, expecting a relaxing soak, only to find the water has turned green. This problem is often combined with a nasty buildup on the walls or cloudy water. But what’s causing it? Well, in most cases, there are a bunch of reasons, but the main troublemakers are algae and heavy metals. Understanding these causes is the first step to preventing and fixing the problem so that your hot tub remains a clean and inviting place for relaxation.

  • Algae growth

The algae you may find in your hot tub is most often small, single-celled plants. It can thrive in a wide variety of conditions and is the primary cause of green water in hot tubs. But how does it get there? The algae is very resilient and won’t die without water, so it can get into your hot tub through wind, rain, or even through the fabric of your swimsuit. Once in the hot tub, algae begins to multiply rapidly, turning the once-clear water into a murky green mess. 

  • Heavy metals 

Though the problem of heavy metals is less common than algae, it can lead to green water too. Metals such as copper, iron, and manganese can seep into water from a variety of sources, such as corroded pipes or the water source itself. When their amount becomes too high, they can react with chlorine or bromine, which are commonly used in hot tubs for sanitizing.

This chemical reaction not only reduces the effectiveness of the sanitizer but also colors the water green. If your hot tub water turns green after shock, you probably have high levels of metals in the water.

If you want to learn how to prevent your hot tub water from turning green, jump right to this part of our article!

Is Green Hot Tub Water Dangerous?

Sure, it looks unpleasant, but is green hot tub water dangerous? Hot tub care experts agree that soaking in such water can be dangerous for your health and hot tub. While green water isn’t very harmful by itself, it can cause a serious imbalance in your water chemistry and damage your hot tub’s pump, heater, and filters. We recommend not ignoring this problem, as it can lead to more serious consequences, such as health problems and the need for expensive hot tub repairs. 

Speaking of the dangers of green water, extended contact with algae can cause skin irritation, but the real problem here are the bacteria. Algae grows actively when there’s not enough sanitizer, like chlorine or bromine, in your hot tub. Under these conditions, harmful bacteria can multiply and make your hot tub dangerous to swim in. 

Heavy metals can leave stains on your hot tub walls and swimsuits. If you have blonde hair, they might even turn it green. Because metals react with sanitizers, they reduce their amount, making them less effective. This weakens your hot tub’s protection and can allow algae and harmful bacteria to grow.

How To Fix Green Hot Tub Water

Green Hot Tub Water

Dealing with green hot tub water can be a frustrating experience, so we’ve put together a simple guide to solve this problem. By following these steps, you will be able to effectively address both algae and heavy metal problems. But let’s first understand how to determine exactly what is causing the green water in your hot tub. 

There are several ways to determine this, the most reliable is to take a sample of your water to your local hot tub or pool store. There, they will test it and tell you what caused the water in your hot tub to turn green. But there is also a simpler way to test it at home. Algae forms a slimy layer on the walls of the hot tub. If you run your hand over the surface of your hot tub and find it slippery, it’s algae. While heavy metals also leave stains, if you run your hand over the wall of your hot tub it will feel squeaky, like a well-washed plate. 

If you are facing a green water problem, and you have an inflatable hot tub, we recommend our guide to chemicals for inflatable hot tubs, so you can choose the perfect product for your hot tub.

❗ Note: Before using chemicals or cleaning your hot tub of green water, protect yourself by wearing gloves and goggles, as chemicals can harm your skin and eyes.

Clean Hot Tub From Algae

If the green water caused by algae has been in your hot tub for less than 24 hours, you can clean your hot tub with a shock treatment. Here is a simple list of steps where we will tell you how to treat green hot tub water caused by algae.

Step 1: Remove accessories. Remove cushions, mats, and any other accessories from your hot tub, so they don’t get in the way of the cleaning process.

Step 2: Shock treatment. Begin shock treatment of your hot tub. This can be done by adding a concentrated dose of chlorine or bromine shock to the water. Be sure to follow the manufacturer’s instructions for proper dosage.

Step 3: Scrubbing. Carefully scrub the walls and surfaces of the hot tub to remove all visible algae. Use a brush or sponge to treat all areas, paying special attention to corners and crevices. Also, don’t forget the hot tub cover, as algae can remain even there.

Step 4: Filtration. Run the hot tub’s filtration system continuously until the water is clear (minimum 12 hours). This will help remove any remaining algae and debris from the water. Do not cover your hot tub during filtration to prevent the high concentration of sanitizer from damaging the hot tub. And don’t forget to run the jets for one or two cycles to clean them, too.

Step 5: Filter cleaning. Once your water is clear, it’s time to clean your filter. It’s important to remove all the algae residue it has collected from your water to reduce the risk of your water turning green again. It’s also important to make sure your filter is purifying your water at a sufficient level.

Step 6: Balance your water chemistry. Make sure the water chemistry is properly balanced. Check the pH, alkalinity, and sanitizer levels with test strips or a kit and adjust if necessary. Balanced water is less favorable for algae growth.

If algae have been in your hot tub for more than 24 hours, it’s better to drain the water completely. This way, you can scrub away all the algae effectively. After cleaning the filter, refill your hot tub, and make sure to balance the water chemistry to keep it clean and safe.

You can also clean up serious algae contamination by using algaecides. They work by disrupting the cell processes of the algae and preventing them from growing. Use an algaecide after shocking when the sanitizer level drops (for chlorine to 3 ppm and for bromine to 3-5 ppm) Add the dosage of algaecide recommended by the manufacturer to the water and run the hot tub filters. You should notice an improvement within a day. If the problem persists, repeat the treatment.

Hot tub water green

Clean Hot Tub From Heavy Metals

If heavy metals are the cause of the green water, follow these steps to solve the problem.

Step 1: Metal sequestrant. Add a metal sequestrant to your hot tub water. This chemical helps bind and neutralize heavy metals. Please follow the manufacturer’s instructions for proper dosage.

Step 2: Filtration. Once the metal sequestrant has neutralized the heavy metals in your water (give it at least 30 minutes), run your hot tub filter to clean the water.

Step 3: Balance your water chemistry. Test your water with test strips or a kit and balance all parameters to normal. First balance the alkalinity, then the pH, and then the sanitizer.

If your hot tub has a severe heavy metal issue, it is best to drain the hot tub completely and replace the water. It is also very important to determine the source from which the metals got into your water. This can be a sign of wear and tear or corrosion on parts of the hot tub, so get a professional to inspect it to be sure your hot tub stays a safe place to relax. 

Simple Steps To Prevent Green Water

Prevent Green Water

Of course, it is always better to prevent a problem than to deal with its consequences. This rule also applies to the problem of green water. Clean water is the result of many chemicals and filters working together. So let’s look at some simple ways to maintain this synergy and keep your hot tub water from turning green. 

What to do to protect the hot tub from algae growth:

  • Sanitize your hot tub regularly. Chlorine or bromine are commonly used sanitizers that help fight the growth of algae and harmful bacteria. If you haven’t decided which sanitizer is best to use in your hot tub, read our article on the difference between chlorine and bromine
  • Test the level of sanitizer at least twice a week using reliable test strips and kits. For bromine, the recommended level is 3-5 ppm (parts per million) and for chlorine, it is 3 ppm. If necessary, adjust sanitizer levels to ensure your hot tub water is well protected.
  • Check and balance the levels of total hardness, alkalinity, and pH in the water 2 times a week as they affect the quality of the water. Balanced water is less friendly to algae growth. 
  • When the hot tub is not in use, put a cover over it. This will prevent debris, sunlight, and other contaminants that can promote algae growth from getting into the water.
  • Filter the water regularly to keep it clean and safe. Remember to clean the filters so that they continue to do their job properly.
  • Regularly clean your hot tub’s interior surfaces, including the walls and floor. If you have been swimming in natural ponds, be sure to wash your swimsuit to prevent algae from getting into your hot tub.

What to do to protect the hot tub from heavy metal issues:

  • Inspect the hot tub each month to prevent wear and tear on its parts. This will also extend the life of your hot tub.
  • It happens that the water is already coming into your home with a high metal content. In such cases, use metal sequestrant every time you fill your hot tub with new water. Add it before all other chemicals to avoid stains.
  • You can also use an additional external filter to clean metals from the water before it even enters your hot tub.

❗ Note: If you are new to hot tub care, we recommend starting with proven hot tub chemical kits that include everything you need to maintain sparkling water.

Hot tub water green


It is always nice to take a dip in clean warm water and just relax. But when green hot tub water comes between you and a peaceful soak, it can seem like an insurmountable obstacle. We understand how difficult it can be to deal with this problem, so we’ve created a simple guide for those who have faced such a challenge.

With the simple steps in this article, you’ll discover why your hot tub water turns green, how to fix it, and learn simple steps to prevent it. Remember that the clean and inviting hot tub is just a few steps away from you. 


🏊 Is it safe to go in green hot tub water?

Green water is often a sign of algae growth or heavy metals, which can make the water murky and potentially lead to skin irritation or discomfort for bathers. This color indicates water quality problems, so we don’t recommend going in a hot tub with green water.

⚡ What should I do if the hot tub water turned green after shocking?

In some cases, if the hot tub water contains dissolved metals such as copper or iron, shock treatment may cause them to oxidize and precipitate. This can result in a greenish tint to the water. In most cases, the green color of water after shock treatment is a temporary problem and the water should clear up within a day as the filtration system removes the contaminants. However, if the problem persists, you need to clean your hot tub from heavy metals.

🤔 Why is my hot tub water green?

The most common cause of green hot tub water is algae growth. They begin to thrive in water with low sanitizer levels. In rare cases, it is due to high levels of heavy metals in your water. They also lower the level of sanitizer in water, which can lead to algae growth.

💧 How to get rid of green hot tub water?

To get rid of green hot tub water, you’ll typically need to shock the water with a sanitizer, scrub the tub’s surfaces, clean or replace the filter, and balance the water chemistry. In severe cases involving heavy metals, you might need to drain and replace the water. You can learn more about how to clean a hot tub of green water in our article.

😱 Why does the hot tub water turn green after adding bromine?

Adding too much bromine to a hot tub can start a reaction between the bromine and some impurities in the water. As a result, the water may take on a greenish or brown color. Please be careful as such water can cause strong irritation to the skin and eyes and negatively affect the lungs. Also, if your hot tub water contains high amounts of heavy metals such as copper or iron, adding bromine can cause them to oxidize and give the water a greenish tint.

🌊 Will green water go away without my help?

Green water in a hot tub is unlikely to disappear on its own. You usually need to take specific actions to remove the underlying causes of green water, such as cleaning the water of algae or heavy metals and restoring the proper water chemistry.

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Peter Rossi