Too much chlorine can cause cloudy water

Water in the pool is milky: why is it? | 5 causes

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Are you the proud owner of a pool, but it just turns milky in color? Cloudiness in the pool water always indicates a problem, which in most cases is caused by errors in use or cleaning. If you have the same problem, it is important to determine what is causing it. This is the only way to use a suitable method of treatment without the pool water becoming even more cloudy or milky.

Pool water is milky

Many people wonder whether cloudy water in the pool is dangerous for their own health. Since the most common cause of a cloudy pool is dirt particles, this question is quite legitimate. However, you can swim with peace of mind even in milky water, as long as the pool doesn't smell bad. If the water starts to stink badly, the filling water has in most cases tipped and has to be completely replaced. Milky water in the pool is in itself only a cosmetic factor that can only become harmful to swimmers after a long period of time without treating the cause. So don't take too long to fix it, especially if the swimming pool has been cleaned too infrequently.

tip: If the filling water is left standing for an extremely long period of time, it will be contaminated with bacteria such as Legionella or Escherichia coli. These represent a high health risk and are represented in particularly high numbers if the water in the pool is particularly cloudy or milky and has an unpleasant odor.


The water in the pool can become cloudy and milky for a variety of reasons. Since these are not immediately recognizable at first glance, you have to compare the individual causes in order to be on the safe side. In total, there are five reasons why your pool water can discolour so intensely. These are explained to you in detail below so that you can take action against them quickly and effectively. Note, however, that such cloudiness does not just appear overnight. It is a slow process that lasts for days or weeks and is therefore not immediately noticeable. Of course, other reasons can cloud the pool immediately, but these are mostly accidents with materials that do not belong in the pool. For example, if you use sediment in your garden and it gets into the fill water, it will likely become cloudy.

Neglected cleaning

The number one cause of a milky pool is neglect of pool maintenance. If you don't clean your swimming pool regularly, the fill water will become cloudy over time as a large number of dirt particles, organic materials and organisms build up in it. Chlorine and a filter pump are not sufficient here, you have to lend a hand to stop the cloudiness, because after two to three weeks it can become problematic. The following components can be responsible for cloudiness:

  • Seaweed
  • leaves
  • Branches
  • Pollen
  • blossoms
  • bacteria
  • Viruses
  • insects
  • Insect larvae
  • hair
  • Cream residues
  • earth
  • sand

This list gives you a rough overview of the components that can make up a pollution. Algae and rotting materials in particular are responsible for milky water, as these become suspended particles. If these suspended particles collect in large numbers, the water in the pool becomes intensely cloudy, which can appear milky. Because of this, to fix this problem, you need to regularly clean the pool. It is particularly important to combat the algae, which can appear after two weeks. So don't miss your regular cleaning routine, which should be done every or two weeks:

  • Collect materials such as leaves or insects
  • Brush the floor thoroughly
  • Brush the pool walls thoroughly
  • Vacuum the floor
  • Don't forget to clean the skimmer
  • clean the filter pump if necessary
  • replace cartridge filter if necessary
  • Check filter system
  • Execute shock chlorination at the end

With these measures you will keep the water as clean as possible. If you want to avoid dirt in the swimming pool, you should put on a cover. This protects the pool water from deposits and materials such as leaves and can save you a lot of effort in maintenance. If your pool water is cloudy, you should also follow the steps above. Cleaning is the ideal solution to your problem.

Note: If you use too many cleaning agents and disinfectants, the filling water can also become cloudy. Even when it comes to pool maintenance, less is more, and you should not overdo it with the use of resources.

Missing disinfectants

Sometimes pool owners do not provide the fill water with sufficient treatment agents to ensure clear water. Since pools have a permanent water cycle, the funds in the pool water decrease over time and the effect is significantly weakened. This leads to cloudiness in the pool that appears very milky. So if you have a clean pool and you clean it regularly, but it starts to become cloudy, you need to freshen up the disinfectant. Depending on which disinfectant you use, you will also need to use this regularly. Only regular use will help ensure that the pool is not cloudy and that the water is pleasantly clear that you can use for bathing and swimming. Above all, you have to pay attention to how often the individual methods have to be used in order for the disinfection to work effectively at all. The following overview will help you:

Suitable disinfectants

1. Chlorine

Disinfection with chlorine is the typical variant. Chlorine granules and tablets are quite cheap and can be used without any knowledge of what makes them so popular. Chlorine is topped up at a pH value of 7.0 to 7.4 as soon as the content is below 0.5 mg / l. In this case there is clearly too little chlorine in the water and should be topped up.

2. bromine

Bromine is similar to chlorine and can be used in the same way. Here, however, the values ​​differ significantly. On average, you have to add bromine to the filling water every fourteen days or when the content falls below 3 mg / l.

3. Active oxygen

When you use active oxygen, it is more difficult to establish a regular rhythm. Since active oxygen behaves differently in the pool than chlorine, a measuring station is usually used here, which shows exactly when the disinfectant has to be used again. There are oxygen tests for private use. If the level falls below 5 mg / l, it should definitely be topped up.

4. UV

The use of UV light to disinfect the pool is also interesting for many people. This is switched on as soon as the filter pump is used. If you forget this, the UV effect cannot be used, which means that the pool is not disinfected. So don't forget to switch on your UV system.

Be sure to check how you disinfect your swimming pool and whether you have forgotten something or have not refilled for too long.

tip: If the pool water becomes milky after shock chlorination, too much or too often chlorine was used, which is usually visible after a short exposure time. In this case, you should simply wait for the chlorine level to drop or drain a little water and replace it with fresh water.

Faulty filter system

Another problem that can quickly lead to cloudy water in the pool is a filter system that is either damaged, improperly adjusted or clogged. These issues are often overlooked as the filtration system is still active and the pool water is being filtered. However, the performance is significantly weaker and so the number of microorganisms and dirt in the pool increases, which in turn leads to cloudiness. For this reason, check regularly whether your filters are clogged. This can clean the filling water again within a short time.

Note: Cartridge filters must not be used together with flocculants. In contrast to sand filter systems, these clog and ensure that the pool water becomes heavily polluted and milky within a short time.

Alkalinity too high

The water values ​​in the pool have to be right so that it does not tip over. If individual values ​​are incorrect, this leads to the water in the pool being milky and cloudy. An often overlooked cause is high water alkalinity. This is understood to mean pH values ​​that are well above 7.4 and can even damage the vinyl and metal components in the swimming pool. The consequence of this is also a clouding of the water, which you can improve by lowering the pH value. In this case, do a test to measure the pH. If this is not between 7.0 and 7.4, but significantly higher, you have to lower it. Hydrochloric acid in granulate form is usually used for this. The dosage can be found in the manufacturer's instructions. It depends on the size of the pool.

Calcium hardness too high

The calcium hardness can also be too high if the pool is milky and cloudy. Compare a high calcium hardness with milky tap water, which contains a lot of lime and is quite hard. The same thing happens if there is too much calcium in the water, which can be recognized by deposits on the walls, floor and pipes. This is lime, the content of which you can reduce using the following methods:

  • partial water exchange
  • use softer water
  • Use water softener

Make sure that the calcium content does not exceed 400 ppm. It should also not fall below 150 ppm. The pool water only becomes milky if the calcium hardness is too high.