Green pool water – Make and keep it clear


Clear cloudy or green swimming pool water in 5 easy steps.

  • Step 1Remove all debris from the pool. Green water is usually caused by too much "dirt" in the pool. This is food for the algae.
  • 2nd step – correct the pH value of the pool water. The pH is usually too high due to the addition of chlorine. Chlorine does not work well at too high a pH. We recommend one pH of 7.2 to 7.3.
  • 3rd stepperform a chlorine shock with HTH Granulate (69% calcium hypochlorite). This is the product with the highest concentration of chlorine. Dissolve the chlorine granules in a bucket of water or a watering can and dose in the green swimming pool.
  • Step 4 - usage Flovil Shock for the water with shock flocculant back clear to make. 1 tablet for 40m³ every 4 to 5 days Dose Bayrol Clarifyer Anti Alg.
  • 5th step - let the filter pump to continuously circulate the pool water and purify. Backwash regularly and add fresh water as needed

4 handy products against green water selected by our specialist

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TIP : the addition of swimming pool products or pool chlorine will affect the pool water values. That's why you need the so check the pH value and the chlorine value regularly. We recommend 2 checks per day when the pool water is green and you want to get it clear again. If everything is in order, a 2 to 3 day check-up is sufficient.

Make green swimming pool water clear

Green pool water after thunderstorm

The water in your swimming pool can turn into a green swimming pool in a single day during a thunderstorm. Underlying is the cause of this the pH value not set to 7.2 – 7.4 and a shortage On ACTIVE free chlorine.

FAQs, frequently asked questions about green swimming pool water and the answers.#FAQS_frequently asked_questions_about_green_swimmingpoolwater

Are algae harmful to health

Harmful algae

Yes, some blue-green algae (cyanobacteria) are harmful to health by inhalation, skin contact or ingestion. Certain types secrete toxic substances (toxins). You can therefore become ill if swallowed or your skin may show irritation when there is contact with the algae.

These algae are RARELY found in private swimming pools. Therefore, the chance that you will become ill from algae growth in your swimming pool is rather small.

How do algae get into the pool?

The presence of algae is an indication that the water is not properly disinfected. This means that bacteria can also be present. You can disinfect better with pool chlorine.

These bacteria are also a danger of disease, ear infections and other health risks.

It usually takes 2 to 5 days before your swimming pool water is clear and pure again after a treatment against green swimming pool water. Speed up clearing the pool by rinsing the filter frequently, vacuuming extra and running the filter continuously.

After performing the 5 steps :

  1. remove dirt
  2. correct pH
  3. chlorine shock met chlorine granulate
  4. add flocculant
  5. vacuum + rinse the filter daily

You can use the pool water faster back clear and pure make by the filter installation to operate 24/24, 7/7 days, this is in manual mode. This way the water in the pool can be filtered continuously.

Do too daily backwash, then you can add fresh water and you will also dilute it a bit. Or if you have one cartridge filter, rinse it daily out.

It is a third piece of advice extra vacuuming or the pool robot run continuously that the settled and present dirt is continuously removed from the pool.

You can prevent green swimming pool water with 3 products; the 5 in 1 chlorine tablets with anti algae, the Bayrol clarifyer anti algae and the HTH Chlorine sticks without stabilizer.

The first product prevents algae growth due to the presence of anti alpha (copper sulfate) in the product. You can see this by the blue dots. This product will specifically fight the algae. So it's an awful lot easier to deal with this one chlorine tablets work instead of the default chlorine tablets 200g.

The 2nd product is specially designed by Bayrol to prevent algae growth. The intention is that you add an amount of anti-algae product to the swimming pool water on a regular basis.

The third product HTH Chlorine Sticks does NOT contain a stabilizer. As a result, the chlorine is always active free chlorine and available for proper disinfection. As a result, you do not run the risk of overstabilizing the swimming pool and thus getting algae formation.

READING TIP : Prevent green swimming pool water with HTH Chlorine.

As a final tip, we can say that you best cover the pool, so no dirt enters the pool (= food for algae). In addition, much less light can enter the water. Algae need light for growth and multiplication.

So if you remove the light source you prevent photosynthesis and growth of algae in the pool water.

AQT Liquid chlorine lost packaging 2023 col

Shock with liquid chlorine or HTH Chlorine granulate

The fastest way to make green water blue again is with NOT stabilized chlorine shock as; of liquid chlorine or HTH Chlorine granulate.

A very drastic and risky method is with liquid chlorine. There's a big risk of it splash or stains but there's no denying that liquid chlorine cares instant blue water. However, we do not recommend this, given the risks.

The alternative chlorine without blocking stabilizer

A better alternative is the use of NOT stabilized, free active chlorine such as the HTH Chlorine granules. You can dissolve this in a watering can and distribute it over the pool. This also ensures a very effective killing of the algae in the green swimming pool water.

After the chlorine shock, the pool water will no longer be green, but it may still be cloudy. This milky water is caused by the presence of the dead algae.

That's why you use a flocculant such as Flovil Shock or AQT Flocculant cartridges to make the pool water crystal clear again

Do I have to empty my green pool

No, you do not need to empty your pool if it is green due to algae growth. You can be the green one algae in the pool best kill by correct swimming pool water treatment and with pool chlorine.

When you empty the pool, not only are the algae gone, but your pool water is also lost. Therefore, the cost of the water balance products and the cost of heating are lost.

This causes a extremely high cost price for emptying, which does not outweigh proper treatment to kill the algae.

This can be done in 5 simple steps:

  1. remove all debris from the pool with the shovel net
  2. check the pH and adjust to pH 7.2 – 7.4
  3. enter one chlorine shock out with HTH Chlorine granulate
  4. let all the dirt stick together with a good flocculant
  5. vacuum and let the filter work continuously 24/24 & 7/7

Usually the water will be clear and pure again after 2 to 5 days. An additional tip is to rinse the sand filter or the cartridge filter every day.

If you pool robot have it run continuously and clean the filter well after each cycle.

Algae not harmful to the filter installation

Green swimming pool water and algae as such are not harmful to the swimming pool installation in itself. Thread algae can get stuck in the filter basket of the filter pump, but they do not cause damage to the swimming pool installation.

However, algae are a sign that the water balance is lost. A disturbed water balance, such as a pH value that is too high or too low, can cause damage to the installation.

The treatment to make green swimming pool water clear again and to kill the algae is also potentially harmful to the installation. After all, you have to perform a chlorine shock to kill the algae.

This high concentration of chlorine in the swimming pool water can cause damage in the long term.

So ensure a constant water quality to protect the filter installation from damage as much as possible.

The best way to obtain a stable water quality is to treat the swimming pool water with a automatic pool water treatment.

What is the cause of green water in the swimming pool?1TP5What_is_the_cause_of_green_water_in_the_swimmingpool

The cause of green water in the pool is the presence of too much dirt, It lack of a cover An blocking the chlorine by overstabilisation.

Too much dirt and strong sunlight

Swimming pools, but also ponds can turn green during the summer. The green color can vary from dark green to light lime green. The cause of this is a “bloom” or very strong growth of very small algae, phytoplankton. The flowering or growth is caused by:

  • the presence of “food = dirt” in the water
  • the strong sunlight (UV)

To get rid of this algae, in other words the green color, it is sufficient to remove the nutrients from the algae. Therefore, you need to clean the pool. Algae can kill you – kill it with a chlorine shock. You perform a chlorine shock with HTH chlorine granulate or with liquid chlorine. These 2 types of chlorine do not contain a stabilizer and therefore have a very high concentration.

Overstabilization and blocking of the chlorine

Chlorine tablets 200g and the regular Chlorine granules are less suitable because they contain stabilizer. This stabilizer allows your swimming pool over-stabilised get. The permitted amount is 70ppm and you can measure it with the Test strips 6 in 1 . Cyanuric acid stabilizer can lower you by diluting the water in the pool. (add fresh water)

Because of this risk of blocking of the chlorine due to over-stabilisation, we recommend the use of unstabilised HTH Chlorine sticks or the Chlorine tablets MTF 5 in 1. But with an automatic swimming pool water treatment with liquid chlorine, for example, you do not run the risk of overstabilisation.

READING TIP : learn all about pool chlorine

What is the best anti-algae product against green swimming pool water

Prevention is better than cure. You can with an Anti Algae product PREVENT the pool water from turning green. But using the Antialgae product when the pool water is already green is efficient. There are 2 types of desalgin. The most famous is the Anti Algae Bayrol Clarifyer. You can also dose this product weekly as a preventive measure to kill green algae in the swimming pool.

The 2nd known anti green water product is the AQT Winter product. The wintering product is mainly intended to prevent algae growth in the swimming pool during the winter months.

What type of flocculant should I use in my pool?#which_type_of_flocculant_should_I_use_in_my_pool

Coagulation - flocculation

Below you can see how you can get the cloudy and green swimming pool water clear and clear again with coagulant. This is a flake product usually based on aluminum sulfate or polyaluminium chloride.

In the first image you can see the water with the dirt particles. The 2nd image shows the flakes of the flocculant with the dirt particles. Finally, in the third image you can see how the flakes settle to the bottom.

  1. the most known and used flocculant tablets are the so-called “stockings" also cartridges or flocfix bags. This type is ideal for rregular preventive use. The flake tablets or flake stockings are easy to use and can be placed in the skimmer basket.
  2. liquid flocculant frequently used in public swimming pools. In private swimming pools you can dose the flocculant and let the flocs “settle”. Once settled you can vacuum them away to the sewer. In public baths it works automatically. This aautomatic dosing of flocculant ensures an improved filtration of the filter sand. This ensures a reduction of the bound chlorine (stinging eyes) and a better clarity of the pool water.
  3. flake powder can be dosed directly into the pool or can be first dissolved in a bucket of water and then dosed. This can be like Shock are applied. The flocculant will clump the dirt together and allow it to settle in the pool. After the dirt has settled, you can vacuum it up and pump it to the sewer.

Overview of the different flocculants to get clear swimming pool water.

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Improve your filtration with a high bed filter and AFM filter glass.#improve_your_filtration_with_a_high-bed_filter_and_filter_glass

  • A first improvement you can make is a sand filter with a HIGHER filter bed
  • The 2nd step is to replace the filter sand with ==> AFM Activated Filter Material filter glass
  • 3rd ultimate step is one of killing 2 birds with 1 stone. Work with one frequency controlled pump. the slower filter speed not only ensures better filtration but also lower energy consumption / lower energy bill

How higher the sand bed, so the more filter sand there is in the sand filter, the better your water is filtered will be. the use, especially with larger filters, of filter sand with different grain sizes also has a very positive effect. Adding to that,  how “slower” the water passes through the filter the better the water filtration works.

To make your green swimming pool water clear again, we also look back at public swimming pools. Therefore, the legislation prescribes a flow rate of 30m³/h/m² and a minimum sand – bed – height of 1m for. That is precisely why people usually place them in public swimming pools hydro anthracite, a type of coal, to absorb the residual products of the chemical reaction.

READING BLOG : The ABC of pool maintenance

On the Vito website you can find a lot of technical information about swimming pool water treatment:

How can you measure the pH value in your swimming pool water?#how_can_I_measure_the_ph_value_in_swimmingpoolwater

One of the main pool values to PREVENT green pool water is the pH value or acidity of the pool water. There are several ways to measure the pH value in your swimming pool water. The quick (but less accurate) way is to measure with test strips. With these test strips you can also measure the chlorine value of your swimming pool water. A second possibility is to measure the pH value with the Hanna pocket pH meter.

Original price was: € 435,00.Current price is: € 399,00. incl. VAT

Preventive tips to prevent green swimming pool water#preventative_tips_to_prevent_green_swimming_pool_water

  • Love your PH value always on 7.2 to 7.3
  • Joint enough chlorine come on with chlorine tablets and MTF chlorine tablets 5 in 1
  • brush your pool regularly with a pool robot
  • Usage flocculant every 14 days
  • Cover the pool with a summer cover or a roller shutter
  • Backwash regularly for a properly functioning and clean sand filter
  • Replace your filter sand with filter glass
  • Replace your filter pump by a energy efficient pool pump which can circulate the pool water longer and slower
  • Place one automatic pool water treatment.

The green swimming pool water after the winter, a holiday or after a storm is actually easy to get clear and ready again. This task seems insurmountable and you tend to it POOL TO EMPTY and refill, however this ABSOLUTELY NOT HAVE TO.

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2 thoughts on “Groen zwembad water – Helder maken en houden

  1. Manon says:

    I have a question about flovil shock. Our pool is 28m3 of water, if I add a tablet of flovilshock it will be for 40m3….will the water not become milky due to overdosing?

    • Lode T Kindt says:

      Hi Manon,
      thank you for your question. You really have to watch out for this. If you dosed too much you would get a breakdown in the filter and flocs IN the swimming pool (which you have to suck up and pump to the sewer with a manual vacuum cleaner) instead of on the filter (which you can rinse away). However, 1 tablet for 40 m³ is also possible for 28 m³, so you will not encounter any problems.

      This problem will only occur in the event of a serious overdose, eg one tablet 3 days in a row.


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