Swimming Pool Flocculant: What is It Good For in Pool Maintenance?

A Pool Flocculation is useful in pool maintenance. But for what exactly do you need the flocculant in your swimming pool, and when is it worth using?

The pool flocculant is used to filter colloidal substances such as sweat, saliva, grease, sand, and other fine particles from the pool water. For this purpose, the flocculant binds the fine particles (0.01 µm to 5 mm) to form large flakes and enables filtration in the sand filter system.

This article explains everything about flocculation in your pool and when it makes sense to use it.

What is the flocculant good for in the pool or hot tub?

According to studies, every bathing guest in the swimming pool carries around 0.5 grams of the so-called colloidally dissolved impurity into the pool water even after a thorough shower.

The colloidal particles are all substances that pollute the pool and make the water cloudy.

This table shows the colloidally dissolved substances in pool water:

Particle Size Pool Maintenance
Sand, hair, dandruff 100 µm – 5 mm Sedimentation, Filtration
Dust, pores, pollen 0,5 – 100 µm Filtration with and without flocculation
Saliva, mucus, fats 0,01 – 1 µm Flocculation + Filtration
Urea, sweat, iron bis 0,01 µm Activated carbon filtration, oxidation

Flocculation is carried out in a pool so that the pool water does not tip over due to pollution by colloidal substances.

The flocculant (coagulant) binds the particles shown in the table to form large flakes and enables filtration – I will explain how the flocculant works exactly below in the text.

Only with a suitable pool flocculant, you have a chance to remove the fine dirt particles and get crystal clear pool water.

The flocculant binds the finest particles and acts as support against existing dirt and cloudiness in your pool.

Tip: In my blog, I explain how to use the flocculant in a pool. Simply click on the link to access the article.

What types of swimming pool flocculants exist?

A distinction is made between two types of flocculants, and these would be:

  • Liquid pool flocculants from the bottle.
  • Solid pool flocculants in the form of pillows/pads/tablets or granules.

The solid flocculants are placed in your skimmer or a cartridge filter.

It doesn’t that much matter which variant you choose in the end.

The solid agents continuously release the flocculant and can be used over a long period.

Tip: I always recommend using some flocculants for general pool maintenance or a pool shock with chlorine to improve your filter performance.

In my blog, I have written detailed instructions for using the various flocculants.

Does the flocculant help with algae and green water?

The use of the flocculant can help to purify the greenish-colored pool water.

However, it must be mentioned that you cannot keep a pool clean in the long term with the pool floc alone.

Usually, the flocculant is added to the pool water for the finishing touches to get crystal clear pool water.

The pool flocculant must be distributed through a filter system over a certain period, depending on the size of your pool.

A combination of a disinfectant (chlorine, active oxygen, bromine), the pool vacuum, and the sand filter system makes a big difference in your pool maintenance.

Nevertheless, the flocculant is recommended if you attach great importance to a hygienically perfect pool and take a step towards chlorine-free pool maintenance.

How the flocculant works in the swimming pool

While the pool vacuum for mechanical pool cleaning and chlorine to disinfect the water is required, the flocculant is also a piece of essential pool equipment.

The general function of the swimming pool flocculant is crucial for the quality of your pool water.

But how does the flocculant work in the pool, and is it really necessary if chemical cleaning agents are already in use?

The colloids (droplets or particles), which move in the size dimension in the nano- or micrometer, repel each other due to their negative charge.

These colloids are also present in apparently clean water due to their physical state.

By adding the positively charged flocculant, the negative charge of the colloidal substances is canceled, and the particles are bound to form visible white flocks that can be easily filtered out.

To put it simply: The fine flakes bind together to form large flakes (fragments), which are then more easily caught by the pool sand filter.

This effect also supports the cleaning work of a pool robot – you can read about a pool robot in my blog.

This video demonstrates how the flocculation works in a pool:

The flocculated dirt collects in the sand filter system and does not end up in your pool water again.

It is necessary to empty the stored dirt from the filter system over time.

This is easy to do with backwashing the sand filter system – follow the link for detailed instructions in my blog.

Please note that using a swimming pool flocculant alone is not enough to clean your pool permanently.

The flocculation in the pool is only used for the finishing touches for clear pool water and does not prevent the formation of algae, like chlorine, and other disinfectants do.

Flies and other bugs must be removed from your pool using different methods. A proven option is to use a practical pool vacuum.

What happens if there is too much flocculant in your pool?

The flocculant can easily be overdosed and will damage your health.

Some experts even claim that if you overdose on the flocculant, the flocculant particles cancel each other out, and the effect is completely lost – but this has not been scientifically proven.

For this reason, it is advisable to adhere to the manufacturer’s recommended amount or the general ratio of 5 to 7 OZ (150 – 200 ml) per 10 m³ of pool water.

The cleaning process with the flocculant can, if necessary, be repeated up to 5 times – without potential health risks from residues.

If the pool water is milky and cloudy, overdosing on the flocculant in the pool will not help. In this case, further measures are required.

Do filter balls work in combination with a flocculant?

I wouldn’t say I like the filter balls and recommend the tried and tested filter sand.

But the flocculant can be used if you also use filter balls. Experience shows that the filtering result will not be better than with basic filter glass or filter sand.

In most cases, the flakes are not held back by the filter balls and return to the pool.

In addition, the backwashing makes cleaning the filter balls more difficult.

Is it necessary to clean the swimming pool with a flocculant?

Since colloids (fine turbidity) are discharged and bound with the help of flocculation, the question arises whether this step in pool maintenance can not be bypassed simply by using enough chlorine, algaecide agents, vitamin C, and fine filter materials?

Especially when you take the time factor into account.

The question is: Is the flocculant necessary in your pool?

Flocculants are only necessary as a supporting component in the fight against algae.

An algaecide works more specifically to eliminate the algae in your pool.

On the other hand, replacing the flocculant with chlorine and vitamin C is insufficient, since the effect of both chemicals cannot encompass the size range of the colloids in your pool water.

The colloidal particles are simply too small – to filter them out of the pool water – as shown in the table above in the text.

Conclusion: The use of the flocculant in your swimming pool is, therefore, a fundamental step in pool cleaning.

But to enjoy crystal clear pool water with the highest water quality, the following must be observed when flocculating your pool:

  • An ideal pH level in the pool is 7.2 to 7.6.
  • The general ratio of flocculant to water – 150 to 200 ml per 10 m³ of pool water.
  • A general waiting time of 6 to 8 hours after using the pool floc.
  • Compatibility of the agent with the filter medium – ideally a sand filter system.

Is the flocculant in the pool water toxic?

Any contact with chemical cleaning agents in excess and improper handling poses a danger to people and their environment.

In a nutshell: The dose makes the poison.

Don’t worry if you’re wondering whether a flocculant is toxic and dangerous.

Flocculants are nothing more than simple binders that bind fine particles into flakes to be better filtered.

A flocculant is – correctly dosed – harmless to humans and not toxic if you use the agent in the pool according to the instructions.

Please note the recommended amount of flocculant in your pool, especially the general waiting time of 6 hours before you can swim in your pool again.

The time intervals can vary depending on the product/manufacturer, and it is advisable to observe the attached product information so that the agent is filtered to the fullest.

Water treatment also relies on flocculant so that we can all get clean and clear water from the tap at home. Source.

Nevertheless, one should always avoid inhaling the flocculant and avoid direct contact with the eyes or skin, as the flocculant has a corrosive effect through direct contact.

Do you have any further questions about swimming pool flocculants?

Contact me at @contactswimfool on Twitter, Facebook, Pinterest, and all other popular social media – I’ll be happy to help.

Have fun using the swimming pool flocculant.

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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.

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