Pool Flocculants - What Are They? The Ultimate Guide

Flocculants are one of many different products available to us pool owners for fixing problems that arise with our water chemistry.

Often considered one of the strongest options available when it comes to dirty pool water, flocculants are effective enough to make even the muddiest water come clean without draining and refilling your pool.

In this article we will talk about what flocculants are, how they work, and the difference between clarifiers and flocculants. We also include a detailed guide for how to use flocculants in your pool, as well as our top recommended products. Let’s jump in!

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What Are Flocculants?

Pool flocculants are a group of products that work to coagulate (clump together) tiny particles of debris in your water that can be impossible for your filter to remove on its own.

Flocculants work to restore water clarity and overall pool cleanliness, and they can make cleaning up even the most disrupted swimming pools a much easier process.

Flocculants are often used in pools where clear water has been unachievable through other methods.

Cloudy water can be the result of many different pool conditions, and once many people have tried traditional approaches like shock treatments, algaecides, and balancing their pool’s alkalinity, they can often be at their wit’s end as to what is polluting their water.

In addition to fixing more stubborn causes of cloudy water, flocculants can even work magic on pools that are straight up muddy.

Following extremely heavy rains, pools can sometimes accumulate severe amounts of ground runoff-based pollution. Flocculants make a great step in the process of revitalising your pool after a heavy storm or weather related flooding.

How Do Flocculants Work?

Sometimes called ‘drop-out’ due to the effect that they have on pool contaminants, flocculants work by reacting with the superfine particles of debris that are present in your pool’s water, causing them to clump together and increasing their density.

This increase in density ultimately results in them falling to the bottom of the pool and accumulating in a thick, gel-like substance.

The name flocculant comes from the field of chemistry, where in more precise terms this process involves the coagulation of particles of sediment that have become indefinitely suspended in a solution and are unable to sink on their own due to a low density that is not much different to the water they are in.

Pool floc works like glue to stick clumps of debris together, causing them to become large and heavy. These clumps of debris sink to the bottom of your pool, where they must then be vacuumed out to waste.

Flocculants are fairly fast-acting in terms of their effectiveness when compared to similar water clarifying products that are available on the market.

Flocculants vs. Clarifiers: The Pros and Cons

Pool flocculants are similar in nature to products known as clarifiers. As with flocculants, clarifiers also cause superfine particles of debris to stick together in clumps, however, clarifiers themselves are slightly less effective than flocculants.

It may help to imagine that clarifiers are slightly less sticky in nature than flocculants, so even though they work in the same way, they form much smaller clumps.

The clumps formed by clarifiers are intended to be made large enough to be removed by your filter system without causing any damage to your filter.

In contrast, the waste that accumulates on the bottom of your pool while using a flocculant must be removed by vacuum because it is too thick for your filter to process without creating clogs.

While clarifiers are intended for mild to moderate problems in water clarity that involve tiny particles of debris, flocculants are capable of handling problems ranging from more moderate to severe.

Flocculants are often used to recover pools in areas where storm surges and other extreme flooding has taken place, and are capable of helping you remove much more dirt and debris from your pool than clarifiers.

Flocculants also tend to work much faster than clarifiers. Even if your pool’s condition is not severe, flocculants have an almost immediate effect on water clarity, and the cleaning process can be completed in as little as seven hours.

On the other hand, clarifiers can take days to work because your filter has to run constantly to slowly remove the coagulated debris. If you don’t have too severe of a problem and are just looking for a less labour-intensive treatment for your pool’s condition, clarifiers may make a fine choice in your situation.

Read more over at our guide to clarifers vs flocculants.

How To Use Flocculants

Here are the basic steps you need to follow to properly use pool flocculants.

#1 - Balance pH

Before using a flocculant, you will need to balance the pH levels of your pool so that they fall between 7.4 - 7.6.

This is the one chemical property that must be altered before introducing a flocculant, because an abnormal pH can negatively impact the effectiveness of the product.

To increase your pH, you will want to use soda ash, and to decrease your pH you will need to use a dry acid. It is not necessarily helpful at this point to balance your chlorine, as flocculants can work fine with or without this chemical present in the water.

The exception to this is if you are dealing with an algae outbreak. Algae must be killed with chlorine before a flocculant can effectively react with their dead cells to settle them out on the bottom of the pool.

#2 - Set pump to recirculation

After balancing your pH, you should then set your pump to a recirculation setting that bypasses the filter unit. If this setting is not available on your pump, consider removing the filter cartridge in your system.

You should not allow a flocculant to circulate through your filter for any reason, as this could cause permanent damage to your equipment.

It should also be noted that certain types of flocculant, such as those designed for commercial use, are intended to be used with the pump shut off completely. Always check the instructions provided by your product manufacturer to ensure you are using your product safely and effectively.

#3 - Add pool flocculant

Then, you will want to add your floc. Most flocculants come in a liquid formula, but the concentrations of these vary, and many formulations require that you pre-mix them in a bucket before adding them to your pool.

Your product should have dosing instructions that will inform you how much product to add based on the volume of your pool in litres. If you cannot locate this information, contact the retailer that you made your purchase from.

#4 - Turn off pump

After letting your pump circulate the flocculant for about an hour, you will then want to shut your pump off and let the water stand.

Depending on the product you chose, it should only take about 5 hours after this point until all of the debris in your pool has settled to the bottom and is ready to be removed by vacuuming.

Some flocculants must be left to sit in your pool for longer periods of time, such as up to 12 hours. For this reason, many pool owners prefer to introduce flocculants before they go to bed and then vacuum the accumulated waste at the bottom of the pool first thing in the morning.

#5 - Vacuum to waste

Set your pump/filter to waste and then begin vacuuming your pool. This should be done manually and at a gentle pace to avoid stirring up the piles of debris at the bottom.

Don’t run this vacuumed sludge through your filter!

Remove as much debris as you are able to see. You may want to consider taking a break near the end of your vacuuming process to allow any stirred up waste to settle down again before you finish vacuuming for a more thorough clean.

#6 - Return pump/filter to normal settings

After you are done vacuuming your pool, you can once again turn your pump to the filter setting.

#7 - Refill water and rebalance water chemistry

Vacuuming will have significantly lowered your water levels and the pool will need to be refilled with fresh source water.

Once you have topped off your pool, test your pool’s chemistry using a test kit and make any necessary changes to adjust your pool’s levels back within the normal ranges.

Debris that is coagulated by a flocculant is unlikely to leave the pool on its own. If, after treatment is completed, you notice more gel-like debris on the bottom of your pool during swimming or other maintenance, you should vacuum or net it out.

Our favourite flocculant product is Algon Floc, available in a one-litre jug that can be used to dose a pool up to 50,000L in volume.

This flocculant is highly effective on even the murkiest of pools and works in as little as 5-6 hours, which is around half the wait time of other products available on the market.


Although flocculants can seem intimidating if you’ve never used them before, they’re a powerful tool for achieving pool cleanliness.

Even after other attempts to clean, sanitise, scrub, or balance your pool’s chemistry have failed, a flocculant can help you remove any and all remaining debris and particles stuck in your water.

Do you have any questions about pool flocculants or how to use them? Let us know down in the comment section, we’d love to help!

Louis from Pool Advisor


A chemical engineer by trade, Louis is committed to debunking myths in the pool industry by explaining the underlying chemistry and making it accessible to all.