Why is My Hot Tub Water Green and How to Fix It

The water in your hot tub should be crystal clear and not green. But why does the water in the hot tub become green, and how to fix it?

Green water in the hot tub is caused mainly by green algae or by incorrect use of chlorine or bromine. The green cast in the water can be removed with a brush and a shock treatment. After 24 hours, the hot tub should be crystal clear again.

In this article, I will show you how to get rid of green water in a hot tub.

Why is my hot tub water green?

In most cases, the water in the hot tub becomes green because of a faulty salt cell.

When enough scale, minerals, and dirt accumulate on the salt cell, it prevents free chlorine from being produced during regeneration. As a result, your pool or spa will be filled with chloramines and turn green.

The best way to determine if this is your issue is to check the surface of the salt cell for scale and dirt.

Cleaning your salt cell can solve this problem – when you buy a new one, make sure you follow the manual setting instructions.

How to clean the salt cell?

If you want to clean your salt cells yourself, make sure you follow these instructions:

  1. First, turn off the system and remove the power supply (cord, cable, or fuse) from the electrical service box.
  2. After turning off the system, pour about 1/2 gallon of non-scaling muriatic acid into your hot tub.
  3. This will dissolve any calcium deposits on the salt cell. If you don’t have muriatic acid, use hydrochloric acid.
  4. As soon as all calcium has disappeared, switch on your pump and fill your pool or hot tub.
  5. Let the water run without interruption until it runs clear again, then stop the pump and turn off all system equipment.
  6. Now you can start using your salt cell again.

Another reason why your hot tub water is green is organic dirt, metals, copper, or most likely green algae.

The green algae attach themselves to the sides of the hot tub and produce a green layer that cannot be removed by standard hot tub maintenance.

You have to use a special chemical product that kills the algae. This will prevent them from causing problems in your hot tub.

Info: The temperature of your hot tub plays an important role when it comes to algae.

How to get rid of green hot tub water?

Luckily, several products on the market remove algae and get rid of green hot tub water.

The first product is called algae clear.

You can buy it at your local pool or spa dealer – Follow the manufacturer’s instructions when using this product to clean your hot tub.

Another chemical you can use to kill all algae in your hot tub is chlorine shock.

You have to be very careful when using this product as it contains a high chlorine level.

If you don’t use the correct amount, some parts of your hot tub or pool will become foam or slippery due to too much chlorine – as always, follow the directions from the manufacturer!

Another option to get rid of your green hot tub water is a manual cleanup.

It takes some time, and you have to be careful not to damage the lining in your hot tub while removing algae with a brush on a pole.

  1. First, turn off the pump and remove all electrical supplies (cord, cable, or fuse) from the electric box.
  2. Then you can start removing the green layer with a pool brush. This procedure will be more difficult if your hot tub has a jet system – it is recommended that you temporarily remove them to clean the walls thoroughly.
  3. After removing most algae, turn on your pump and pour some chlorine into the water to clean it. The chlorine level must be above 3 ppm – this is called a hot tub shock.
  4. Let the filter run for 12 to 24 hours after you shocked your hot tub.
  5. In the end, the hot tub should be clean.

After you clean the green water in the hot tub, you should keep an eye on water balance and optimize your filtration.

Your water must stay clean, so you should use less chlorine possible to prevent health risks.

However, if algae keep coming back, maybe a salt system combined with an Ozonator is the right tool for you- this will permanently remove all algae!

How long to wait after cleaning the hot tub?

How long do you have to wait before going into the hot tub?

This depends on how strong your chlorine level was during the cleaning process.

If you shock your hot tub (with a high chlorine level), it is recommended that you wait at least 24 hours before using the hot tub again.

Before you use your hot tub, test the chlorine and pH levels.

The chlorine level in a hot tub should be between 1.5 and 2 ppm, and the pH level should be between 7.2 and 7.6.

If the chlorine level is too low, there will be a risk of infection!

Can too much bromine turn the water green?

Yes, bromine can turn the water in a hot tub green if you use it too much, but this is only temporary!

It takes 1 to 3 days for the bromine level to go back to normal.

Tip: You can reduce the bromine level in the hot tub by simply changing 1/3 of the water.

Bromine turns the water in your spa green because bromine reacts with algae in the water, which causes a chemical reaction that turns your bromine into bromide.

This then attaches to algae and gets mixed with other elements in the hot tub, turning it green.

Why spa water has still a green tint?

Water from the spa with a greenish tint is water that contains chlorine.

It contains chloride ions (Cl) derived from chlorine.

This greenish color occurs when sunlight shines through the clear water to the bottom, where it is colored by plant life.

The green tint is due to an organized movement of photoreactive substances. A protein molecule called phycocyanin is the primary pigment in the photosynthetic bacteria that produce the green coloration, but other molecules are probably involved as well.

These pigments absorb visible light (wavelength 400-700 nanometers) efficiently, but they do not absorb ultraviolet.

Sunlight passing through the water that has been colored by these photoreactive substances produces a green tint in the reflected light.

Should you drain your hot tub to get rid of green water?

If you follow my steps, the water in your hot tub should be cleaned quickly.

But sometimes, the algae come back in a short period of time.

In this case, you can drain your hot tub.

However, this is a big job. After draining the hot tub, you have to deep clean the surface.

After cleaning the hot tub, refill the hot tub and use chemicals like chlorine or bromine to keep it clean.

If your manufacturer tells you to use an efficient tile cleaner, it may not be recommended that you drain the hot tub.

If this is unclear to you, do not hesitate to contact your hot tub retailer.

Is it safe to swim in green hot tub water?

You should not use your hot tub if it is green.

Green hot tub water is caused by an imbalance of the ph or chlorine that can harm you.

Negative effects are:

  • Itchiness of the skin
  • Irritated eyes.

If your hot tub is green because you have a problem with algae, you should know that most algae are harmless to humans.

But it is also possible that the green algae produce a toxic substance that can lead to breathing problems or even harm your liver.

The harmful effect of algae is only a risk when the algae have been eaten.

So, don’t eat green algae!

It is important to maintain your hot tub to prevent green water!

I will give some extra tips on how to prevent green algae in your hot tub.

How to prevent my hot tub from turning green?

Prevention is better than cure!

You can keep your hot tub water crystal clear by following these steps:

  • Make sure you check your sanitizer levels regularly – use test strips (available at most stores) to test the spa water.
  • Balance the total alkalinity to 80 – 120 ppm, the pH level at 7.2 – 7.6, and the calcium hardness at 200 – 400 ppm by using recommended chemicals.
  • Place a hot tub shock product in your hot tub every month to keep it clean.
  • Use a hot tub cover when the hot tub is not in use.
  • Clean or change the filter cartridge regularly – depending on the size of your hot tub, this should be done every 2 to 4 weeks.
  • Change the water in the hot tub at least every 2 months.
  • Start using a stabilizer (conditioner) when filling up your hot tub, so you reduce the risk of your water becoming green.
  • Use a salt-chlorine generator (electrolyzer) instead of regular chlorine.
  • Clean the surface of the salt cell regularly with a brush.

Remember that algae can be dangerous in hot tubs.

If they’re not removed immediately, they will multiply and take over the surface of your hot tub.

Don’t let this happen, don’t wait, and don’t hesitate to contact a professional.

Do you have any further questions how to fix green water in your hot tub?

Contact me at @contactswimfool on Twitter, Facebook, YouTube, or Pinterest – I’ll be happy to help.

Have fun in your clean hot tub!

Photo of author
Hi. I'm Max Berg. I've been in the pool industry since 2015 and have always felt drawn to water. I'm the author behind swimfool.com, where I share my years of experience in pool maintenance and give helpful tips on keeping a swimming pool or hot tub clean. My tips reduce the costs of water treatment and protect the environment.

Keep Reading