The water in my pool is clear but has a green/brown tint... what can I do?

How can I recognise an iron oxidation problem?

  • The pool water turned colored after adding disinfectant.

    It turned green or brown

  • The water used to fill the system comes partly from a borehole

    The iron present in the water oxidized after a disinfectant was added.

If your problem does not correspond to these symptoms, it is possible that your pool is experiencing a similar problem.

Actions to effectively combat green/brown water

  1. 1

    Check the TAC

    If the TAC is below 80 mg/L, increase it with Alca-Plus®. > Alca-Plus®

  2. 2

    Adjust the pH of the water

    with pH-Minus or pH-Plus. Adjust the pH to between 7.0 and 7.4 if you are treating with chlorine. For bromine treatments, adjust the pH to between 7.4 and 7.6. With a balanced pH, treatment products are more effective. > pH Minus, pH Plus, Quicktest, Pooltester Electronic, Pooltester pH/Cl

  3. 3

    Perform a shock treatment

    to neutralize all impurities and microorganisms present in the water.

  4. 4

    Add a flocculant

    Place one Superflock Plus flocculant cartridge in the skimmer basket every 7 to 15 days for pools equipped with a sand or glass filter (if you have a cartridge filter, use Superklar). > Superflock Plus, Superklar

  5. 5

    Filter 24/7

    until the water is crystal clear again. Then resume your normal daily filtration routine. If necessary, replace the filter material (sand, Eco Filterglass Plus, or AFM).

  6. 6

    Wash the filter

    Then restart the filtration system until the water is clear and transparent. If the water is still not crystal clear, replace the Superflock Plus cartridge in the skimmer.

  7. 7

    Prevent metal deposits

    To protect your pool, add Calcinex as soon as you fill it. This will prevent new limescale deposits and stains or discoloration caused by metals. > Calcinex®

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Green or brown swimming pool water: frequently asked questions (FAQ)

  • If the pool water changes colour after adding disinfectant, this is not usually a problem caused by algae, but rather a result of iron oxidation. The water can turn green or brown within a few hours. This is a common occurrence when the water used to fill the pool comes from a borehole. The iron present in the water reacts with chlorine, bromine or active oxygen, causing this discolouration.

  • If your pool water is clear but has a green or brown tinge, you are dealing with an iron oxidation problem. The treatment must be adjusted accordingly.

    After correcting the TAC and pH, carry out a shock treatment to oxidise the metals. Add a flocculant if you have a sand filter, or a clarifier if you have a cartridge filter. Run the filter 24 hours a day until the water becomes crystal clear again. Clean your filter, then prevent metal and limescale deposits with Calcinex to stop stains or discolouration caused by metals.

  • Brown water following a top-up with borehole water is almost always due to the presence of metals, particularly iron. This is a common occurrence: the water appears clear at first, but turns brown or green after the disinfectant is added. The iron oxidises and becomes visible.

  • Here are the steps you can take to tackle green or brown water:

    1. Check the TAC and adjust the water’s pH.

    2. Carry out a shock treatment.

    3. Add a flocculant or clarifier.

    4. Run the filter 24 hours a day; clean the filter.

    5. Prevent metal deposits.

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