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Why is My Hot Tub Water Green? (Causes and how to fix)

A relaxing soak in your hot tub can quickly turn into a distressing experience when you notice the water turning green. That may leave you asking “why is my hot tub water green?”

Hot tub water can turn green due to algae growth caused by inadequate sanitization or imbalanced pH levels. To remedy this, shock the water with a sanitizer and balance the pH. But adding an algae remover can clear up the green color faster.

CLICK HERE to see the algae remover on Amazon that I like best.

Regular maintenance and proper water testing are key to preventing algae and keeping your hot tub water clear. But don’t despair; we’ve got you covered with a fresh perspective on tackling this common issue.

In this comprehensive guide, we’ll not only help you understand the causes of green hot tub water but also provide you with actionable solutions and preventive measures to keep your spa oasis crystal clear and inviting. So let’s dive into “why is my hot tub water green” and how to fix it.

Short Summary

  • Green hot tub water is caused by algae invasion, insufficient sanitization, and metal contamination.
  • Prevent green hot tub water with consistent sanitization, scheduled filter cleaning, and regular monitoring of chemical levels.
  • Follow a step-by-step guide to fix existing green hot tub water involving thorough cleaning, shock treatment, and achieving the right balance in your spa’s chemistry.

Causes of Green Hot Tub Water

Believe it or not, there are a few culprits behind the green tint in your hot tub water. The primary causes include algae invasion, insufficient sanitization, and metal contamination.

In the following sections, we’ll delve deeper into each of these causes and explain how they can wreak havoc on your once-pristine spa water.

Algae Invasion

Algae invasion is a very common reason for having green hot tub water.

This growth of algae can be easily prevented by regular maintenance of the spa. Algae thrive in warm water that hasn’t been treated with enough sanitizer, such as chlorine. When the cover is left off or if the sanitizer levels are consistently low, algae can spread quickly, turning your hot tub into an unsightly, slimy mess.

The presence of dead algae can also be indicated by not only a green tinge but a slippery coating on the interior of your spa, which can come in various colors, including black and mustard.

Apart from being an eyesore, algae can consume bacteria in your hot tub, which in turn can lead to poor water quality and potential health risks. To prevent algae growth, it’s crucial to maintain proper sanitizer levels and keep your hot tub covered when not in use.

I will say, however, that if your hot tub has a cover that is regularly used whenever the hot tub is not in use, an algae problem is unlikely as it needs sunlight to grow.

Insufficient Sanitization

Another factor that can lead to green hot tub water is insufficient sanitization. When sanitizer levels are low or infrequently shocking occurs, it creates an environment conducive to algae growth.

However, green tint is not always caused by algae; excessive metals in the water, either from the heat exchanger or the source water, can also result in a green tint. Keeping your hot tub water clean and well-sanitized is vital in preventing the growth of algae and ensuring a pleasant spa experience.

Metal Contamination

Imbalanced water chemistry is another culprit behind green hot tub water, as it can lead to algae growth. Low pH levels, for instance, can facilitate the proliferation of bacteria, leading to the discoloration of the water and the dissolution of copper from the heating element into the water.

Introducing an oxidizer to water containing heavy metals can also cause the minerals to become activated, resulting in a green hue in the water. To prevent green hot tub water caused by metal contamination, consider using a solution like EcO, which can help maintain water balance and keep your spa water crystal clear.

Step-by-Step Guide: Fixing Green Hot Tub Water

Now that we’ve identified the potential causes of green hot tub water, let’s explore a step-by-step guide on how to tackle this issue and restore your hot tub to its former glory. These steps include:

Thorough hot tub cleaning. – Filter maintenance. – Refilling with filtered water. – Spa cover care. – Shock treatment. – Regular water testing. – Achieving chemical balance.

Thorough Hot Tub Cleaning

The first step in addressing green hot tub water is to drain and clean the hot tub thoroughly with a hot tub cleaner, bleach, or distilled vinegar.

A deep cleaning is essential to eliminate the water containing algae and thoroughly clean all surfaces to ensure the complete removal of the algae. While cleaning the hot tub, don’t forget to wash the spa pillows and deep clean the filters as well.

During the cleaning process, it’s a good idea to use a hot tub test strip to measure the total hardness, total chlorine, free chlorine, alkalinity, and pH levels of the water. If heavy metals are detected, utilizing a sequestering agent can be an effective solution for removing them from the water.

Filter Maintenance

Maintaining your hot tub filters is crucial to prevent green hot tub water caused by algae. To clean the filter, remove it from the hot tub and rinse it with a garden hose. If the filter is beyond cleaning, you’ll need to replace it with a new one that is compatible with your hot tub.

Simply follow the manufacturer’s instructions for proper installation.

Refilling with Filtered Water

Once your hot tub is thoroughly cleaned, it’s time to refill it with fresh water. Using filtered water helps prevent metal contamination and ensures that your hot tub water remains clean and clear.

To knock this out easily, use a hose filter to remove minerals and other contaminants from the source water as you fill your hot tub. It just screws onto the end of the hose so it couldn’t be simpler.

This top-rated one on Amazon is a great choice and at a fantastic price!

Spa Cover Care

Cleaning the hot tub cover is an essential step in preventing bacteria and algae growth. If you find algae spores on the cover, clean it with diluted bleach, diluted cleaning vinegar, or a vinyl cleaner. Be sure to follow the cleaning product’s instructions for the best results.

Not only does cleaning the cover remove residual algae, but it also helps maintain the cover’s lifespan and effectiveness in keeping your hot tub water clean and free of debris. A well-maintained cover is crucial for maintaining the overall cleanliness of your hot tub.

Shock Treatment

After cleaning and refilling your hot tub, it’s time to perform a shock treatment.

Shock treatment involves adding a significant amount of oxidizer (same as shock) to the hot tub to inhibit algae growth. This process eliminates any remaining algae spores in the water and ensures your hot tub remains clean and free of algae.

Shock treatment is also beneficial for maintaining the chemical balance of your hot tub water.

While you can get non-chlorine shock, if you have green spa water, cloudy water, or a scum line, and want to get crystal clear water, I would highly recommend chlorine-based shock.

CLICK HERE to get the chlorine shock I use from Amazon.

Regular Water Testing

Regular water testing is a crucial step in maintaining the cleanliness and safety of your hot tub water.

At least once a week, test the water using test strips or a smart monitor to assess the chemical composition and make necessary adjustments. Regular testing allows you to detect changes in water chemistry that may signify potential water safety issues, such as contamination or imbalanced chemical levels.

When adjusting chemicals, it’s important to follow the recommendations provided by the test strips or smart monitor to achieve the optimal water chemistry for your hot tub. Proper water testing and chemical adjustments help ensure a safe and enjoyable hot tub experience.

Achieving Chemical Balance

Maintaining chemical levels in your hot tub is essential to prevent green water and sustain optimal water chemistry. To achieve chemical balance, add chemicals according to any imbalance detected, test the water, and repeat the process until the ideal levels are reached.

Additionally, using a digital pool monitor, such as EcO, can provide alerts and recommendations for maintaining the optimum water quality of your hot tub. By closely monitoring and maintaining your hot tub’s chemical balance, you can ensure the water remains clean, clear, and safe for you and your loved ones to enjoy.

Preventing Green Hot Tub Water

Now that you’ve successfully tackled the green hot tub water issue, it’s time to focus on prevention. By implementing consistent sanitization, scheduled filter cleaning, and water chemistry monitoring, you can keep algae at bay and maintain a pristine spa experience.

In the following sections, we’ll provide detailed guidance on each of these preventive measures.

Consistent Sanitization

Regular sanitization plays a vital role in preventing green hot tub water and keeping algae growth in check. For hot tub owners, especially those with Master Spa models, using chlorine is the most effective sanitization method, as it works well with the mineral filtration system.

To maintain proper sanitizer levels, be sure to keep your hot tub covered when not in use, especially during the summer months when chlorine levels can deplete more rapidly. Consistent sanitization not only keeps algae at bay but also ensures that your hot tub water remains safe and clean for everyone to enjoy.

Scheduled Filter Cleaning

Regular hot tub filter cleaning is another crucial aspect of preventing green hot tub water. Cleaning your filters at least once every three weeks at the kitchen sink with a sprayer. Then about every 3 months, use a filter cleaner for a chemical soak to help eliminate debris and stave off algae growth.

Additionally, extending filter cycles can help remove unwanted materials, such as dirt, bacteria, and algae, contributing to cleaner and clearer hot tub water. By keeping your filter cartridge clean and well-maintained on a regular basis, you’ll be one step closer to maintaining a pristine hot tub experience.

Water Chemistry Monitoring

Monitoring your hot tub’s water chemistry is essential to detect any potential water safety issues, such as contamination, and to take the necessary steps to prevent them. Regularly collecting samples and examining the chemical composition of your hot tub water ensures its safety and helps maintain a delightful spa experience.

The process involves sampling and analyzing water constituents and conditions, identifying any potential water safety issues, and implementing corrective action. By staying vigilant with water chemistry monitoring, you can maintain a safe and enjoyable hot tub environment for you and your loved ones.


In conclusion, green hot tub water is a common issue that can be caused by various factors, such as algae invasion, insufficient sanitization, and metal contamination.

By following our step-by-step guide, you can effectively tackle the problem and restore your hot tub to its former crystal-clear glory. Remember, prevention is key: maintaining consistent sanitization, scheduled filter cleaning and water chemistry monitoring will help you keep algae at bay and ensure a safe and enjoyable spa experience.

Don’t let the green hot tub water ruin your relaxation time. Armed with the knowledge and practical solutions provided in this guide, you can confidently enjoy your hot tub, knowing that you’re prepared to tackle any green water issues that might arise. So go ahead, take a dip, and let the soothing waters of your hot tub wash away your worries.

Frequently Asked Questions

Is it safe to go in green hot tub water?

It is not recommended to use green hot tub water.

While it could be from high mineral content in the water, it could also be algae, and it’s definitely a sign of a chemical imbalance.

Therefore it’s best to not get in until you have figured it out and fixed it.

If the discoloration has occurred for less than 24 hours, it could be a simple fix; otherwise, it’s best to thoroughly clean the hot tub before use.

Will shocking a hot tub get rid of green water?

Shocking your hot tub is the best way to get rid of green water. Hot tub shock treatment involves adding chlorine or bromine to break down any algae buildup in the lines.

But this Clorox Algae Eliminator on Amazon works VERY QUICKLY if the cause is algae.

Why is my hot tub water green after shocking?

Shocking your hot tub may cause the water to turn green due to the oxidization of the minerals present in the tub. These oxidized minerals can react with copper, creating a color change.

But usually the green color goes away after a few minutes and is not considered harmful. But to prevent this from happening, try using metal removal products like my favorite one on Amazon: Metal Be Gone from Leisure Time.

That will reduce the mineral content in the water.

Can you over shock a hot tub?

Yes, it is possible to over shock a hot tub. Doing so can cause skin and eye irritation and may also lead to bleached swimwear.

Therefore, it is important to stick to the manufacturer’s instructions when adding shock to your spa.

How to get rid of green water in hot tub?

It’s easy to clear green water from a hot tub – just follow this simple advice. First, remove the cover and any pillows while the hot tub is not in use. Then, add 60g of sanitiser (chlorine or bromine) per 1,500l of water and turn the jets on for one cycle.

With this solution, you should see results within 12 hours and will have crystal clear hot tub water again.

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Jeff Campbell