The Difference Between Pool Clarifier and Flocculant

The Difference Between Pool Clarifier and Flocculant

Cloudy pool water is usually caused by dead algae or mists of particles suspended in your pool water. The job of a coagulant agent, like clarifier or flocculant, is to clump these tiny particles into larger clumps so that they can be collected by your filter or flushed to waste. 

Now, clarifier and flocculant (floc and vac) are two sides of the same coin. Both are types of coagulant agents that accomplish the same task using different routes. The key differences are the time it takes for the reaction to take place and the extra elbow grease needed from you to finish the job. We will discuss the pros and cons and the best times to apply which chemical. 


clarifier clears cloudy pool
Cloudiness can floating dead algae


  • Least amount of work for the user 
  • Great for light cloudiness and superfine silt 


  • Takes several days to get the desired result 

Pool clarifier is a mild coagulating agent that boosts your filter’s cleaning capabilities by clumping small dirt particles into larger particles your filter media can trap. Safe to use with sand, DE and cartridge filter systems, clarifier requires that your pump and filter are run continuously for at least the first 24 hours for optimal results. 

Clarifier is a milder chemical than flocculant making for a slower work rate. Your pool’s reaction to the clarifier may take a couple of days before you see the results. So, if you are needing a quick fix for a pool party only hours away, clarifier will not be the choice for you.  

Clarifier is the ideal choice for mild cloudiness or a regular part of a cleaning regimen to give your water that extra sparkle.  


flocculant fixes cloudy pool
Flocculant at work


  • Shows results within a few hours 
  • Super effective  


  • Requires vacuuming 
  • Water waste 
  • Can’t be used on systems with cartridge filters (unless there is a bypass) 

Flocculant’s coagulation process is basically a supercharged version of a clarifier. But instead of relying on a pool filter to do the cleaning, it requires vacuuming. Floc clumps the dirt into large clots, so large that they no longer float, dropping all the dirt to the pool floor where you can then vacuum to waste. Your pool should show marked improvement within a few hours of its application, making it ideal for procrastinators (like me) cleaning just before a pool party. 

Floc can be used for mild cases of cloudiness all the way up to murky. However, I usually suggest it as a last resort, because you must vacuum it to waste. You can lose a good bit of water while cleaning the pool. 

Floc should never come in contact with your filter media as the clumping agent can cause havoc. Floc is only suggested for use with filters with bypass options, i.e. sand and DE filters with multiport or slide valves. It is not suggested to use floc with a cartridge system, unless you have plumbed a bypass for the filter.  

So which is best for you? 

Clarifier is best suited for basic maintenance, and picking up straggling silt your filter just can’t seem to catch. Flocculant is best for more severe cases, like part and spring cleanup. Flocculant shows results within a few hours, making it great for cleaning in crunch time. 


22 thoughts on “The Difference Between Pool Clarifier and Flocculant

  1. Dang, my floc said to use “up to” 3 times the recommended dose of 8-oz. per 10k gallons. My pool is 10 k, that would make 3 times the dose 24-oz. I mistakenly added 32-oz. Did I create a problem by adding 4 times the recommended dose?

    1. Using too much floc may cause your pool to become cloudier, and a lot harder to clean. you will have to continue the process of removing floc as you normally would.

      You will also want to keep an eye on your pH, because certain types of floc can make you pH take a nosedive.

      1. Hi, I used flocculant as part of opening this season, had all the levels correct. I’ve used it in the past, have a sand filter, bipassed it. Everything like you should, it has only sat about 9 hours as I put the flocculant in kind of late last night…do I still allow it to sit all day or will the sun cause some havoc on the pool without the filter running for the day? (The water is not yet clear, it still looks like it’s collecting white debris together? ) TY so much!!

        1. I would stick to the instructions on the bottle. If it says to let it set for 18-24 hours, do so. Especially if your water is still cloudy, it’s still got work to do. If your chlorine takes a hit then you can just shock it once the flocculant has been removed.

      2. I mistakenly used flocculant with a cartridge filter so all it does is circulate the debris and make the water cloudy only to resettle again after the pump stops.
        Can you advise how to fix this problem?

        1. Flocculant would usually gum up the cartridge making water flow drop and filtering extremely hard. So, not only would water find it hard to get past your filter, so would any dirt. I believe your cartridge became so gummed up with floc that backpressure caused a tear or two allowing the dirt to bypass the filter. You will need to remove the cartridge and examine it for rips in the fabric and broken bands.

  2. I worked on my pool for 3 weeks last spring trying to clear the water when I opened my pool. I finally researched online & discovered a ‘floc’ product I had never used. WOW!… I had my pool sparkly clear in one day. I did have a lot of water waste from vacuuming but so worth it! I plan to use this process every spring when opening my pool then use clarifier to maintain. Very good article. I wish I had read this last winter.

      1. I just bought and used HTH Floc from Walmart. Did the trick for me and turned my pool clear after I put in the recommended amount overnight (dropped all the debris to the bottom).

  3. Matthew.. great information. I just had my pool resurfaced by a highly rated company using Florida Stucco Gem. We paid additional for a two week chemical “fire-up” treatment. After the resurface was complete and the pool was full of water, the company owner came in and began adding the necessary chemicals. One chemical used (as described to me) was intended to mitigate the water cloudiness associated with pool resurfacing that apparently binds these suspended particles with the intent of them making their way to the filter cartridge and, thus, out of the pool. Except the pool man came to the door the next day to tell us the particles were not making there way to the filter as intended and he advised they had to keep moving and not settle. I brushed a couple of times per day, but did not sleep in the pool and certainly couldn’t keep anything ‘moving’ 24 hours per day. The pool man recommended we replace our filter/cartridge assembly as the one we had was old in his opinion and not working well enough. We agreed and he came the next day to install a new one. As was known from the beginning of this process, we have no operable main drain.

    The next week while taking a swim in my newly remodeled pool, I noticed what appeared to be a 6 inch white spot at the bottom of the pool near the inoperable main drain. I went down to inspect and the area is very porous and not smooth like the area surrounding it. I noticed other similar, smaller areas with the same issue/defect. We asked our pool man about it and his answer was we didn’t keep the coagulated particles moving well enough, some rested on the bottom which damaged the new surface, but nothing can be done at this point. I was floored. Does any of this sound accurate. I am at a loss as to what to do. Please advise, if possible. Sorry for all the words.

    1. First, i would check any paperwork the installing company provided to confirm the aftercare chemical treatment was to be complted by the company or if it was your responsbility. If it was their responsibility and the source of the problem is their malpractice, then they should be responsible for repairing the pools urface.

      If the aftercare was down to you, there should have been a procedure sheet similar to this:

      Yes there should have been something like
      Day 1 – Add 1/2 gallon Muriatic Acid (careful not to breathe the fumes) Let the Pump run 24 hrs a day for 3 days.
      day 3 – Add 1/2 gallon Muriatic Acid then Brush the Pool in the AM and again in the PM. Always clean the filter after each brush. This helps the Plaster rid the calcium.
      Day 4 – Take a Pool water sample to local pool store for Testing and do accordingly.
      Day 5 – 30 Brush 1 time daily and always clean filter after
      This is just for the first 30 days.

      They could spot treat that spot with acid using a PVC adapter

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