Green Hot Tub Water


Green hot tub water leaving you, and your guests, green around the gills?

It can be exacerbating spending long hours getting your hot tub clean and ready for your guests, only to fall embarrassingly short at the “grand reveal”. You removed the cover only to find that the once clean water has turned green in just a matter of days. It’s uninviting to say the least. Aside from feeling a little bashful, it also leaves you questioning, “Why is my hot tub water green, and how can I fix it?”.

Continue reading to discover what has caused your hot tub water to go green, how you can turn it back to crystal clear and what you can do in the future to prevent it reoccurring. If your swimming pool is suffering from similar water discolouration issues, check out this complete guide to pool maintenance for easy to follow hints and tips.

Green Water – The Causes

Green hot tub water caused through metal oxidisation.

There are three main causes of green hot tub water. These factors are highlighted below.

1. Insufficient Sanitiser

Sanitisers, such as chlorine are added to hot tubs to kill bacteria and other unwanted nasties. One of those unwanted nasties is algae. Without adequate sanitiser levels in your hot tub, algae can proliferate quite rapidly and cause the water to go green. The green tinge is attributed to the cell growth, or bloom as it is often referred to.

2. Oxidation of Copper and other Metals

Oxidation of metals in the water, such as copper is also proven to turn hot tub water green. This process produces copper carbonate that interacts with the water to leave a green tinge. The original source water and some supplementary hot tub additives may contain high levels of copper. Copper can also be introduced into the water by an interaction between the water and metal components, such as the air jets or the heater element. Copper is often utilised in the heater element due to its heat conducting properties.

3. Pollen in the Water

A lesser known cause of green hot tub water is pollen. Pollen is a fine powder produced by the male part of plants. It is effectively planted sperm and is required for sexual reproduction. I digress. Pollen grains are extremely small and lightweight. They float easily and are carried by the wind. Trouble is, pollen can accumulate in your hot tub and your filter may struggle to remove such minute particulate matter, hence the yellow & green colouration it adds to the water.

Green Water – How to Turn Crystal Clear

Hot tub with crystal clear water.

So, what can you do about green water? There are two routes that can be taken to eradicate the problem.

Option 1 – Treat the Existing Water

With the right treatment, you can remove the green from the water and return to enjoy clean hot tub water.

Assess your hot tub water: Feeling the inner surfaces of the hot tub will give you some helpful insights as to what may be causing the problem. For example, a cloudier green colour and surfaces that are slimy to the touch generally indicate an algae problem. If the water is green, and yet still clear, it may be due to a high concentration of oxidised metals. If it’s pollen, it is more likely to settle to the bottom of your hot tub, creating an ominous looking cloud ready to be stirred up at the gentlest of agitations.

Removing Algae: For an algae problem treat with an appropriate algaecide. Brush the surfaces of the hot tub before adding these chemicals to enhance the effectiveness of the treatment. Also, allow the pump to continue to run in order to circulate the additive.

Removing Oxidised Metals:For an excess copper issue, adding a sequestering or chelating agent will cause metal ions to group together in complexes that are easier to filter out of the water. It is important to clean or replace your filter after using a sequestering agent.

Removing Pollen: Pollen accumulation can be remedied by the addition of a flocculant. A flocculant is a substance that causes smaller particles to group together into larger ones, making them easier to filter out.

Option 2 – Drain the Water & Refill

This method is best for those with a bit more time on their hands and who want to ‘start afresh’. Be sure to completely Drain the water from the tub: Depending on the model of your spa, drainage can be achieved via a plug hole or via a suction hose.

Cleanse the spa and filter: Spray down the surface of the hot tub with a spa cleaner. If you do not have any to hand, try a mixture of four parts water to one part white vinegar. Remove the filter and rinse with a garden hose. Next spray with a filter cleaning chemical and leave for around 30 minutes before thoroughly hosing it down. To go one step further, we also recommend an overnight chemical soak, leaving the filter submerged in a concentration of filter chemicals. Once removed rinse thoroughly.

Fresh Fill: Refill the hot tub using a hosepipe. Depending on the pressure of the water and the size of the tub it can take anywhere between 1 and 3 hours.


Whilst unsightly, green water doesn’t have to be a long-term problem for your spa. With a choice of remedies, at a low cost and effort, you can return the spa water to its usual crystal clear state.

If you have a busy schedule, it may be overwhelming thinking about what may be causing your green water problem let alone the many other issues surrounding the state of your hot tub.

The solution? CleanMyHotTub can take care of your hot tub maintenance for you. Our affordable cleaning and maintenance packages are a winner when it comes to managing your hot tub and ensuring it is healthy and running at its optimum.

Avoid green water embarrassment. Be confident at your next “grand reveal”. With CleanMyHotTub, you or your guests are sure to not feel not green around the gills at all, but rather, beckoned to experience your most inviting hot tub.

2 thoughts on “Green Hot Tub Water

  1. Dean says:

    Hi. The water in my bubble spa is slightly green. I have chlorine shocked it and the Ph is spot on and algaecidee levels. How long does it generally take for the water to become clear again?
    Should I check all levels again tomorrow and adjust if required.
    Many thanks

    • Scott
      Scott says:

      Hi, it should become clear after 24 – 48 hours. If not I recommend a full water change and at the same time leave the filter to soak. Spray it down thoroughly before replacing and monitor it again.

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