The Difference Between Pool Clarifier and Flocculant

Trying to figure out which product to buy for your cloudy pool? Read on to find out whether a clarifier or flocculant is best for you.

Pool Clarifier & Flocculant Quick Answers: 

  1. What are Pool Clarifier & Pool Flocculant?
  2. How do you use a swimming pool clarifier?
  3. How is flocculant different?
  4. How do you use a swimming pool flocculant?
  5. Can you swim with a flocculant or clarifier in the pool?
  6. Can you put too much clarifier or flocculant in a pool?
  7. What is the best pool clarifier?

Is there a better way to spend your day than sitting by a pool, basking in the sunshine? We doubt it. Unfortunately, a cloudy pool can throw off your plans in a hurry.

Cloudy pools are a common issue when first setting up your pool or after an algae bloom – but it can still be upsetting. Don’t fret, though! It’s easy enough to clear up your pool. To do so, you first need to make an important decision: Should you use a clarifier or flocculant to fix the cloudiness during pool maintenance?

What are Pool Clarifier & Pool Flocculant?

A Pool Clarifier is a liquid substance that contains polymers – chain-like molecules that act as coagulants on tiny particles that are too small for your filters to catch. Adding a clarifier causes these tiny particles to clump together and allows your filter to remove them through its regular process.

A Pool Flocculant, otherwise known as pool floc, is a powdered substance. Like a clarifier, it also causes particles to thicken and clump together, but they are larger and will sink to your pool’s floor instead of running through the filter.

We realize these options sound pretty similar. But there are some key differences when you’re considering whether to use a flocculant or clarifier. Let’s review how each pool additive is used.

Warning: Flocculant will not work with a cartridge filter unless you have a custom plumbing setup that allows you to bypass the filter.

How do you use a swimming pool clarifier?

If your pool is just mildly cloudy and you are not in a rush to clean it out, a clarifier may be your best bet. A clarifier requires less work and less water but can take to two to three days to achieve the results you are looking for.

The process of using a clarifier is simple, as long as you follow this step-by-step process. Here  are the 5 key points in using a pool clarifier:

1. Remove any algae

Before using a clarifier, you first need to remove any algae growth. No amount of clarifier will get rid of algae!

2. Check the pH balance

Now test the pH balance of your pool. It should measure between 7.4 and 7.6 for the pool clarifier to be effective.

3. Measure the volume

You will also need to know your pool’s volume to make sure you are adding the correct amount of clarifier. If you don’t already know the volume of your pool, you can use Pool Calculator on your desktop or as our handy app for iOS and Android – to quickly find that number.


Pool calculator provides the necessary tools and pool maintenance info you need to keep your swimming pool & hot tub water clear and balanced.

4. Read the directions and add the clarifier

Finally, add the clarifier according to the manufacturer’s instructions. It’s important to read them carefully, as this process may vary between different brands.

5. Run your filter until the water is clear

Once the clarifier has been added to your pool, turn on the pool filter and run it 24/7 until the cloudiness is gone. This can take two to three days, but swimming in the pool at this time is safe after about 20 minutes.

How is flocculant different?

Flocculants also cause particles to coagulate and clump together, but these clumps are too large for your filter to retrieve and will sink to the pool floor. Flocculants can have your pool cleaned in a day, with no stragglers left behind. The downside is that this process requires more effort on your part – and involves losing a greater volume of pool water.

Also note that you’ll need additional tools, like a water vacuum and a sand or Diatomaceous Earth (DE) filter. 

How do you use a swimming pool flocculant?

As we said above, flocculant is similar to a clarifier but requires a bit more effort. Here are the 9 key steps to follow:

1. Turn on your filter

Again, you need a sand or DE filter to capture the large particles and recirculate your pool water.

2. Balance the pH

The pH balance of pool water for a flocculant should be the same as for a clarifier – between 7.4 and 7.6.

3. Check other pool chemistry

You should also test your pool’s alkalinity, hardness, and chlorine levels before adding flocculant. The handy Pool Calculator mobile app for both iOS and Android makes this process a breeze.

4. Clean your pool filter

Only clean your filter when the pressure gauge has risen to 7-9 lbs. To learn more about how to clean and backwash your filter, visit our post on How to Backwash a Pool.

5. Add the flocculant

Finally, you will need to add flocculant based on the volume of your pool. Excessive flocculant can actually make your pool water cloudier, so you need to get this right! If you do not already know your pool volume, the Pool Calculator app can help you estimate it in moments.

6. Run your pump for 2 hours

After adding the flocculant, run your pool pump for two hours to circulate the additive.

7. Let the pool sit for 8 hours

Now turn off the pump and let your pool sit for at least eight hours. This will allow the particle clumps (aka “floc”) to settle onto your pool floor, where you can vacuum them up.

8. Vacuum your pool

Set your filter to Waste and vacuum the floor of your pool slowly to make sure you do not stir up any particles. If the water becomes cloudy, wait until it settles and vacuum again.

a manual pool vacuum at the bottom of a pool cleaning debris
This is a manual pool vacuum, but you can also do this step with a robotic vacuum.

9. Add water & test levels

After all the particle clumps have been vacuumed up, your pool’s water level will likely have fallen. You can add more water at this point, measure your pH levels, and set your filter to recirculate before entering the pool.

Can you swim with a flocculant or clarifier in the pool?

One of the more common questions we come across is whether it’s safe to swim after adding a flocculant or clarifier to a pool. The answer is: It depends.

If you’ve added flocculant, swimming in the pool is not recommended because it reduces the flocculant’s effectiveness. You should only swim after the particles have sunk and been removed from your pool floor. The entire process of adding flocculant will likely just take one day – but if you or your children are dying to get in the pool, a clarifier will be your best choice. A clarifier is a swim-safe chemical, and you can swim 20 minutes after adding it to your pool.

Can you put too much clarifier or flocculant in a pool?

The simple answer to this question is yes, and that is why it is so important to read the instructions on any brand of pool clarifier or flocculant you use. Too much clarifier can compound your water problems and cause murky water that becomes a breeding ground for bacteria. You can reuse a clarifier after 5-7 days, but if you’re constantly seeing cloudy water, there may be other problems.

Adding too much flocculant can cause its own issues. Flocculant is aluminum sulfate, which is designed to clump with the particles you’re trying to remove. But if you add too much, the flocculant will start to agglomerate with itself instead of those particles. These flocculant clumps will not drop to the pool floor and can clog up your filter. Too much of this product can also cause damage to your pool’s surface and may even injure your skin.

What is the best pool clarifier?

If you decide a clarifier will work best for your situation, there are many options. We’ve done the research and identified two brands that are consistently beloved by pool owners.

First, there’s Clorox Pool & Spa Water Clarifier.

This is one of the cheapest clarifiers you can buy, and has outstanding consumer reviews. This clarifier is safe for all pools and works in 12 hours. With only 1 ounce needed per 5,000 gallons of water, you can also make this clarifier last. The downsides of this product are limited, but you will have to use the product weekly to benefit from it. Note also that this clarifier can only be used for backwash pool filters.

The second major option to consider is Robarb R20154 Super Blue Clarifier.

This product is more expensive than Clorox – but still comes at a very reasonable cost, given that you need only 1 ounce per every 5,000 gallons of water. You can also use this clarifier in a saltwater pool, which is a nice feature. Other benefits are its compatibility with any filter type and effectiveness at all temperatures. This product also claims not to affect pH balance, although we recommend checking your pH balance before and after adding any product to your pool water. The few cons of this clarifier are the increase in nitrates it may cause.

Both of these clarifiers are available online from vendors like Amazon. Whichever product you choose, always follow the directions carefully. As we mentioned above, overuse of any pool clarifier or flocculant can cause cloudiness in your pool water and other problems.

An Informed Choice

Whether you want to relax on your own at the pool or hold a massive pool party, clear water is a necessity! Clarifiers and flocculants are two ways to remove the cloudiness in your pool, and after reading this article, we hope you feel confident about how to use them. For more tips on keeping your pool sparkling clean, brush up on our daily pool maintenance guidelines.


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