Last Updated: November 14, 2021

A Comprehensive Guide to Pool Flocculants: What, When and How

Written By: Pool Care Guide

Pool flocculants and pool clarifiers are excellent ways for you to keep your pool clean. If they aren't a part of your regular maintenance routine, pay close attention. We will discuss what they are, when you should use them, and how they can improve your pool's filtration.

Flocculants Vs Clarifiers

Pool clarifiers are typically used in conjunction with flocculants to ensure all particles have been removed from the water. Flocculants target particles that are larger than 1 micron. Clarifiers, on the other hand, target particles that are smaller than 1 micron.

The main difference between these two products is that clarification changes the physical structure of particles, whereas coagulation reduces their number.

How Pool Flocculants Work

A pool flocculant is an agent that causes fine particles to clump together and settle out of water. This ensures that filtering is more efficient and that algae do not return right away. This process, known as coagulation, improves the clarity of the water by removing unsightly floating debris such as algae and leaves.

If you find yourself with a pool that is cloudy and difficult to keep clean, flocculants provide an excellent solution. They are more effective solutions than clarifiers. However, it isn't all positive. Flocculant downsides include costing a bit more, and using them takes a lot more work.

How Pool Clarifiers and How Are They Different Than Flocculants?

Clarifiers are chemicals similar in composition to flocculants.  They are limited in their use, but they take less effort. You can usually apply them at night or on weekends without disrupting your day-to-day activities.

Clarifiers use enzymes and bacteria to break down organic compounds before they reach the filter or chlorine. This means that there is a build-up of these agents in the swimming pool and chlorination isn't as effective.

Clarifiers work by coating individual bits of grime with a chemical film which causes them to become heavy and sink to the bottom of your pool. Pool clarifiers are typically used in conjunction with flocculants to ensure all particles have been removed from the water.

Everything You Need to Know about Flocculants and Clarifiers

Warning - Don't use flocculants if you have a cartridge filter without a filter bypass

A flocculant is not appropriate for cartridge filters because the tiny coagulated masses of flocculant and contaminants can clog your filter's paper pleats. If you have a cartridge filter and don’t have a bypass, you'll need to use a clarifier instead of a flocculant.

When to Use Flocculants Vs When to Use Clarifiers?

If you have signs of cloudy water, brown stains, or discoloration from hard water or high mineral content, use a pool flocculant.

If you have pockets of grime layered on the bottom of your pool, or unsightly algae floating on the top and want them removed without scrubbing your floors yourself, use a clarifier. Clarifiers are a gentler way to clean the pool with fewer side effects than using chemicals that target larger particles.

And it's worth mentioning that most go hand in hand--using both would be ideal if you're looking to remove these different types of particles from your pool for good.

How to Use Pool Flocculants

There are two main ways to use a pool flocculant: through the skimmer or in-line. Using it in your skimmer is probably easier but not always necessary. If you notice high levels of debris in your water, adding a flocculant directly into your pump basket may be more effective. Flocs may be used in either a pump or gravity-fed system.

Step 1: Raise the Water Level to the Pool's Highest Point

In order to get the best results, raise your pool's water level so that it is at its highest point. This will counter the water loss from the vacuuming that will take place at a later point.

Step 2: Bring the pH to 7.0

This is lower than what the pH should normally be. It's a temporary measure to ensure that the flocs are most effective. If you have a saltwater pool, check your calcium hardness levels before doing this step. It may be best not to do so if they are low already.

Step 3) Dilute the Flocculant

Dilute the pool flocculant in a bucket of water before adding it to your skimmer. If you are using an in-line system, add directly onto the top rail or into the return line where possible.

Step 4) Add a Flocculant to the Pool

While the pump is running, add a flocculant to your pool. There are several ways that this can be done:

  • - Directly into the skimmer basket
  • - In pump filter compartment or basket
  • - In the main drain area of above-ground pools (if equipped)
  • - Around the edges of the pool

Step 5) Run the Pool Pump

The flocculant will work best if you run the pump for a minimum of eight hours. This is about how long the average pool pump takes to circulate water one time.

Step 6) Turn the Pool Pump Off

Now, turn off the pool pump for eight hours. This will allow the flocs to settle at the bottom of your pool and collect the debris that was floating in the water.

Step 7) Set Your Filtration System to "Waste"

If you use a sand filter, this will be the best setting for now. If you have another type of filtration system, consult your owner's manual to see how it should be set during flocculation.

Step 8) Turn the Pool Pump Back to “On”

Once the flocs have settled to the bottom of your pool, turn on your pump so that water is drawn through it. This will remove the debris collected by the flocculant and send it out of your pool's system where it can be filtered or treated for removal later on.

Step 9) Vacuum the Pool

Vacuum the bottom of your pool. This should remove any remaining debris that was collected by the flocculant and may have slipped through.

Step 10) Replace Any Lost Water

If your pool needs to be refilled, do so now. Allow the water level to rise up to the midpoint of the skimmer entrance before checking your pool chemicals. The water reduction followed by the subsequent rise will likely have thrown off your pool's chemical balance.

Step 11) Backwash the Pool's Filters

Finally, backwash or clean your filtration system according to its usual routine so that it can be used to its full capacity once again (this is especially important if you have a sand filter).

Step 13) Final Pool Cleaning and Maintenance

After a pool has been flocculated, it's important to do a thorough cleaning of the area around it as well as any other areas that will come into contact with foot traffic or equipment. This includes skimmers, drains, ladders, and anywhere else that debris may have collected.

Step 14) Add a Clarifier if Needed

Once the pool is clean and free of debris, add a clarifier or algaecide as needed (depending on what type of algae you had before). This will prevent any new growth from forming so that your filtration system can do its job as needed.

Step 15) Monitor and Repeat Flocculation if Necessary

If your pool is still showing signs of debris or algae after flocculation and a full clean-up has been completed, continue to monitor it on a weekly basis for any other changes that may occur.

Depending on how dirty your pool is, you may need to repeat the flocculation process. In order for an effective filtration system, debris of all sizes needs to be removed from the water.

Why You Shouldn't Overuse the Pool Flocculant

While a flocculant is an excellent way to improve the filtration of your pool, it shouldn't be used constantly. Overuse can cause problems with pH balance and cloudy water.

How to Use Pool Clarifier (Step-by-Step)

Step 1) Remove Algae First

Start by removing any algae from your pool with a brush and skimmer. Clarifier doesn't work well with algae because it can inhibit the clarifier from working. It's important that you remove any visible algae before adding a pool clarifier to your pool.

Step 2) Balance pH and Alkalinity

Clarifiers can't work unless your pH and alkalinity levels are balanced. You'll need to check both before you add a clarifier. If either is off, then the pool clarifier will not be as effective as it should be at balancing out those numbers. To balance these items, use a pH increaser or pH decreaser.

Step 3) Measure Pool Volume

You'll need to know your pool volume before adding a clarifier.  You can use our pool volume calculator. If you'd rather calculate it yourself, we have listed all of the relevant pool volume calculations on that same page.

Step 4) Add Clarifier, There are Differences Between Brands

Once you know your pool volume and have balanced pH and alkalinity, it's time to add the clarifier. Not all pool clarifiers are created equal; some brands work better than others, depending on what types of particles need to be removed from your water. The instructions and dosages will change from product to product, so be sure to consult the product label.

Step 5) Run the Filter

Once you've added the clarifier, it's time to turn on your filter and run it until the water runs clear.  Keep in mind that if your pool is cloudy after adding the clarifier, it may take a few days for the water to clear up.

Step 6) Clean the Filter

Finally, it's time to clean your filter. Clarifiers are not kind on the filters and will gum them up quickly if they're not cleaned after each use. You'll need a pool filter media cleaner or cartridge replacement (depending on what type of filter you have).

What Are the Different Types of Pool Flocculants?

There are three main types of pool flocculant: cationic, anionic, and non-ionic. Cationic flocs have a positive charge, while anionic ones have a negative one. Non-polar or non-ionic flocs have no charge.

Cationic Flocs: Cationic pool flocculants are the most common type of floc and come in a range of formulas to suit different needs. They contain a positively charged molecule that works with negatively charged particles such as algae, dirt, metal ions, or bacteria cells.

Anionic Flocs: Anionic flocculants can be used in conjunction with cationic ones to ensure thorough coagulation. They contain a negatively charged molecule that works well when paired with positively charged particles such as algae, dirt, metal ions, or bacteria cells.

Non-Polar Pool Flocs: If you're looking for a more eco-friendly choice, non-polar flocs are the way to go. They contain no charged molecules and rely on natural forces such as gravity or surface tension to work their magic.

What Are the Most Positively Reviewed Pool Flocculants?

Pool Supply World's Pool Perfect Plus

Price: $25.99
Size: 16 ounces and 32 ounces
Rating: Five stars on Amazon .com with over 60 reviews at the time of writing this article.  

This product works well for above-ground pools, in-ground pools, and fiberglass pools alike. It is safe for all pool surfaces and is ideal as a winterizing agent.

Pool Supply World's Winter Guard Floc

Price: $18.99
Size: 16 ounces
Rating: Five stars on Amazon with over 150 reviews at the time of writing this article.

This product works well on all types of pool surfaces and is recommended for use during cooler months. It can be used with any type of flocculant, but should not be combined together before adding to your pump basket or skimmer.

Common Questions and Answers

What are the differences between flocculants and pool clarifiers?

Flocculants are best used to remove debris from the water, while clarifiers work to clear up cloudy or dirty pool surfaces. Clarifiers shouldn't be combined with flocculants as this may reduce their effectiveness.

When adding a floc to my pool, do I add it directly to the water or put it through my skimmer?

If you have a multiport valve with an impeller that's powerful enough for your type of debris problem, use it. If not, you can either add the floc directly into your pump basket and turn the pump to “on,” or use a skimmer directly.

Can I add floc to my pool when it's in the middle of a backwash cycle?

Yes, you can add your flocculant at any time, regardless of what part of the filtration process your pool is currently undergoing. Backwashing and filtering will simply go around the flocculant, so it won't positively or negatively affect filtration.

How long do I need to wait for my pool water to clear up after adding a floc?

If there's nothing in your filter basket and you have well-balanced chemical levels, two hours should be enough time for results to show. If you have a lot of debris in your filter basket, it will take longer.

Is it safe to use with my pool's saltwater system?

Yes, flocs are completely compatible with saltwater chlorine generators. However, you may need to add extra NaCl or Epsom salts if your pH is low when using this type of flocculent in an SWG pool.

Can I reuse any unused product after I'm done?

No, you should never reuse any flocculant or chemical product after it's been used. Can I use pool chemicals with the same formula to clean my house and yard as well?  Yes, but they may not be as effective on non-pool surfaces such as grass and soil so follow all of the label’s instructions.

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