How To Floc A Pool: Easy Guide To Using Pool Flocculant

  • By: John Parker
  • Last Updated: November 24, 2022

There is nothing better than having friends and family over for a pool party. That is until you see how dirty the pool water is!

No need to panic! We’ve got you covered to soon get your pool clear.

Read on to find out how to get that cloudy water clean again with our guide on how to use flocculant for pools.

How To Floc A Pool: Easy Guide To Using Pool Flocculant
A cloudy pool that needs some help from pool floc to clear cloudy water
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Table of Contents

When to use pool flocculant

Pool owners should consider using flocculant if the pool water still seems quite dirty despite regular maintenance.

Generally, pool filters are handy at doing their job and manage to pull out dead algae and insects. However, they are not so great when it comes to microscopic debris and other small particles. This may include viruses, algae growth, and other bacteria.

Flocculants contain coagulant agents that work to gather dirt particles into clumps making it easier for pool owners to see the debris more clearly and as the clumped particles then tend to settle on the pool floor it makes it easier to vacuum.

How to use pool flocculant: A step by step guide

It may seem daunting, but using flocculant is relatively straightforward. Take a look at our easy guide below to help catapult your pool back to cleanliness.

Step 1: Raise the water level

Filling your pool to the maximum is advised as this process requires vacuuming. This will reduce the risk of the water level falling below the filters. If this were to happen, the pumps would not be able to circulate the water efficiently.

To raise the water level, you will need to close the outlet and open the pool’s inlet until you are content.

Step 2: Neutralize the pH level

In a perfect world, the pH level should be 7.0, but realistically, anything around 7.5 is also decent.

So why do you need to balance the pH level? 

Flocculants often affect the pH of pool water in some way or another. Neutralizing this means that if there happens to be a change in pH levels, they won’t be too dramatic.

A bonus is that the pool sanitizer will still work effectively at this level.

Step 3: Diluting time

Now it is time to dilute the flocculant. To do this, you will need to work out the volume of your pool. If that seems like too much work, there will be a rough guide on the back of the bottle which should help.

Step 4: Time to floc your pool

You will need to read the label to work out how much pool flocculant to use for your pool’s volume.

The best way to add flocculant to the pool is to pour it in a few inches from the edge. This will help the chemical spread out equally and will not stick to the pool’s walls.

You will need to add from all pool angles and not just from one side.

Step 5: Turn the pool pump on

Leave your pool pump running for 4-6 hours; this allows the flocculant to spread throughout the pool water evenly.

Step 6: Let the pool sit

After at least eight hours, turn the pump off and allow the pool to sit overnight. During this time, the flocculant will gather dirt in large clumps, which will eventually congregate at the bottom of the pool.

Step 7: Time to turn the pump back on

Once the pool has sat without interference for the night, you will need to turn the pump back on. Any dirt that has gathered along the bottom of the pool can be filtered out.

Step 8: Set the pool filter position to ‘waste’

On this setting the pool pump pulls water from the pool and sends it straight to the waste outlet without letting it pass through the filter; this is effective, particularly when there is a lot of dirt or debris lying at the bottom of the swimming pool.

Step 9: Vacuum the bottom of the pool

Using a manual vacuum the bottom of the pool to remove the dirt that has accumulated there. As the setting is on waste you will lose water from the pool quite quickly so you should work as quickly as possible without disturbing the debris on the bottom.

As you need to work quickly an automatic pool vacuum would take so long that the water level would drop too far. As much as I love my robotic vacuum, it would probably be unable to cope with the amount of debris on the pool floor, so using a manual vacuum is definitely the right tool for the job.

Read my post for full instructions on How to vacuum a pool to waste.

Step 10: Replace any water lost during the process

You’re almost done. Switch off the pump so you do not lose any more pool water. Then one of the last steps is to replace any water lost during the process of vacuuming the pool using a garden hose.

To finish, backwash your pool filters to get rid of dirt and debris gathered during the process. Taking care of your filters is vital for the overall maintenance of your swimming pool. Read my post How to backwash a sand filter.

Easy Guide To Pool flocculant
A crystal clear pool after using floc

Advantages and disadvantages of using pool flocculant

Before you dash out to purchase a bottle of pool flocculant, take a look at our list of pros and cons.


  • Gets to work fast!
    If you’re a hopeless procrastinator then this is obviously for you. Why wait around for 2-3 days when you can get your pool cleaned up in a matter of hours!
  • It’s effective!
    This stuff really does get the job done, and while no pool cleaner on the market is 100% effective, flocculant is a close winner!


  • Requires vacuuming the water to waste
    Vacuuming to waste isn’t always ideal and can be time-consuming. Having to sit around waiting for the water level to increase is just plain boring!
  • Can’t be used in pools with cartridge systems
    As mentioned above, unless your filter has a plumbed-in bypass, flocculant is a huge no-no. The dirt and debris collected by the flocculant can clog the filter which can be costly to fix.

Pool Maintenance Course

When I first bought my house with a swimming pool, I knew nothing about cleaning and maintaining it. I was recommended Swim University’s Pool Care Handbook and video course so I bought it and have never regretted it.

It was probably the best money I spent that year as I have saved thousands by doing it myself.

Different types of pool flocculant

There are different types of pool flocculant which we will discuss below. Some you may prefer over others.

Liquid flocculant

This type of pool flocculant is poured into the pool manually. Our step by step guide above is based on using flocculant in its liquid form.

When using liquid flocculant, you must be sure to follow the instructions set out on the back of the bottle to ensure you don’t add too much. This fast-acting product is useful if you need to clean your pool ASAP.

Cartridge pool flocculant

This is good for pools that require a permanent fix. Cartridge pool flocculant is placed in the skimmer and works as the water passes through the area. It does take time to work its magic, so don’t expect results as quickly as you would with the liquid form.

Tablet pool flocculant

Solid in form, this type of pool flocculant can be placed into the pool or the skimmer. Again, it can take a while to dissolve and disperse to different areas.

Each product we have listed above is effective at removing small and large particles of dirt from your pool. Always remember to read the instructions on the packaging.

Best pool flocculants: A short review

We have compiled a shortlist of the best-rated pool flocculants on the market today. Let’s take a look.

1. HTH Drop Out flocculant swimming pool cleaner

HTH 67029 Drop Out Flocculant Swimming Pool Cleaner, 1 qt

HTC Drop Out will take your cloudy pool water and turn it into crystal clear waters. This product quickly gathers dirt and debris overnight to be vacuumed away the next morning. The formula does not affect pH levels and is easy to administer.

What we like about HTH Drop Out flocculant swimming pool cleaner

  • Can be used in saltwater pools
  • HTH sell a variety of pool cleaning products
  • Ideal for pools containing high levels of algae

2. Pool Mate Drop Down liquid pool floc

Pool Mate 1-2440 Liquid Drop Down Swimming Pool Flocculant, 1-Pack

Pool Mate Drop Down brings both organic and inorganic material together to form clumps. Just half a bottle can clear a 24′ round above ground pool in a matter of hours. For best results, make sure the pH level is around 7.2. This product works best when left without interference for eight or more hours.

What we like about pool mate drop down liquid floc

  • It’s cost-effective
  • Ideal for use in pools that collect pollen from trees that may grow nearby
  • Removes particles that may have congealed over time on the surface of the water

3. Maintain granular floc

Maintain 2405M 5 Pounds Swimming Pool Granular Flocculant, 1-Pack

This powdery substance is ideal if you have a tough job on your hands. Maintain Granular Floc requires the user to mix the granules with pool water before pouring the solution into your pool.

What we like about maintain granular pool floc

  • Ideal for use in areas of tropical climate
  • Sand filter friendly (provided the filter is regularly backwashed)
  • One bottle will last a long time

What’s the difference between pool clarifier and pool flocculant

Cloudy pool water is the amalgamation of dirt particles building up over time. Cleaning chemicals, like pool clarifier and pool flocculant, help clump tiny particles together so that they are big enough for the human eye to see.

So what is the difference between pool clarifier and flocculant? Let’s take a look.

Pool flocculant

Pool flocculant, otherwise known as pool floc, is a fast-acting agent that clumps particles together, which become so heavy that they sink to the bottom of the pool.

Using a pool filter is not enough when it comes to floc, so vacuuming is a must. Within a few hours, your pool should start to look a lot cleaner and clearer.

Flocculant is recommended as a last resort as it can damage filter media. It is fine to use with pools that have sand filters with slide or multiport valves. However, it can cause havoc with cartridge filter systems (unless the filter has a plumbed in bypass).

Pool clarifier

Swimming pool clarifier is a much milder chemical that takes longer to get to work. It can take a day or two to see any results, so if you are in a rush, it may not be the choice for you.

This mild coagulating agent is safe to use with cartridge filters in pools with a cartridge filter system, and sand/DE (Diatomaceous Earth) filters. It is ideal for use in pools that have slightly cloudy pool water and for general year-round maintenance.

How to use pool clarifier

Pool clarifiers are the best option if you want to maintain your pool in the long run. Here’s how to use this product.

  1. Start by running your filter system for 24 to 48 hours. This will help to clear out any residue before adding the solution.
  2. If you find the water is still murky or cloudy, add the recommended amount of clarifier to the water. The amount will be based on the volume of your pool.
  3. Next, you will need to let the pool sit overnight without any interference. This allows the particles to clump together and sink to the floor.
  4. In the morning, vacuum the remaining residue from the pool floor but be sure to keep the filter running.
  5. Take a look at the pool chemical levels, and once they are back to normal you are free to go swimming!

Why pool water becomes murky

There are many reasons why you may have cloudy pool water, and it’s not primarily because of bad weather.

Giving your filter a backwash every once in a while will remove any dirt that is clogging up the system.

You may just need to run your filter system more often. Pool filters should be left running for at least eight hours a day, but try leaving it for 10-12 hours to see if this makes a difference.

An imbalance in pH levels may be the cause. If so, you may need to purchase a pH reducing chemical which will help to clear up murky waters.

It is important to regularly test the pool chemicals, particularly the chlorine levels. Low chlorine, or bromine, can cause algae growth which will turn the water cloudy over time.

Flocculant FAQs

Can you put too much clarifier in a pool?

Adding too much pool clarifier can be detrimental. If you do make this mistake, the best thing you can do is to filter it out. Alternatively, you can drain and refill, however, this is long-winded and time-consuming. Do you want our advice? Just don’t put too much in.

Can you put too much floc in a pool?

Adding too much flocculant to your pool can be damaging as the floc can begin to agglomerate with itself and form clumps. This defeats the object of using the chemical in the first place!

How long after adding flocculant can you swim?

We would recommend holding out for 2-4 hours after flocking your pool. Remember, flocculant is a chemical that can irritate and even burn your skin. Similarly, the chemical may not be as effective if you are in the pool as the water needs to be still so it can evenly disperse itself.

How often should I floc my pool?

Pool flocculants should be added to the water on a regular basis for general maintenance. Taking care of your pool also takes care of the filter system which can be costly if they get clogged up.

Can I use clarifier and flocculant at the same time?

You shouldn’t use these products together at the same time. However, they can be used one after the other. It is important to remember that using too many chemicals can be detrimental to your pool’s environment. 

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