What is Pool Clarifier and When Should You Use It?



You’ve heard of pool clarifier before, but what does it actually do?

In this article, we’ll go deep on clarifier, how it works, and when (if ever) it’s worth using in your swimming pool.

Short answer: Pool clarifier clumps tiny particles together so they can be captured by your filter, else they’ll accumulate and cloud your water.

What is Pool Clarifier?

Clarifier is a chemical that clumps small particles together so they can more easily be removed by your filter.

Most of the contaminants in your water are large enough to be captured by your filter system. However, very fine dirt, metals, cosmetics, algae spores, bacteria, and other organic material can sometimes slip through.

These tiny particles pose little threat to your water at first, but they can continue to build up until it eventually impacts the water clarity — particularly in the form of cloudy or murky water.

This is more often the case if you have a sand filter as sand isn’t as efficient as DE or cartridge filters at trapping small particles. More on that later.

How Does Clarifier Work?

How does a clarifier manage to track down and combine all those tiny particles floating in your pool?

The answer is particle attraction. Without getting too much into the chemistry involved, particles can either be positively or negatively charged, or they can be neither (neutral).

In a swimming pool, tiny particles that derive from contaminants typically have a negative charge, often as a result of being suspended in water.

When a clarifier is added to the pool, it introduces positively charged particles that attract and neutralize the negatively charged particles that are already in the water, causing them to coagulate or “stick together”.

In short, a clarifier acts as a kind of magnet that attracts-to microscopic contamination and causes it to clump together.

What’s the Difference Between Clarifier and Flocculant?

Clarifiers and flocculants both cause contaminants to clump together so you can remove them from your pool more easily.

The key difference is size.

Clarifier creates small clumps that continue to float around in your pool until they eventually get circulated and filtered out.

Flocculant (or floc) creates larger clumps that are heavy enough to sink to the bottom of your pool. As a result, they’re not circulated and removed by your filter but vacuumed out instead.

What’s more, a clarifier works slowly over several days, whereas a flocculant is more aggressive and faster-acting (only 24 hours or so), making it a better solution for dealing with more serious contamination.

When Should You Use Clarifier in Your Pool?

It’s tempting to throw clarifier at the first sign of cloudy water, but that’s rarely the best approach.

Remember, clarifiers (and flocculants) only work on tiny particles, and a cloudy pool is often caused by any number of issues, including.

  • Unbalanced water; pH, total alkalinity, and calcium hardness.
  • A high level of chlorine, particularly after shocking.
  • A low level of chlorine allowing contaminants to linger.
  • A dirty or clogged filter that’s unable to work effectively.
  • Dirty pool surfaces, particularly the walls.
  • Contamination from heavy use or environmental factors

In other words, you need to rule out all other potential causes by testing and balancing your water, ensuring you have the right amount of chlorine, as well as thoroughly brushing your pool surfaces, and cleaning your filter.

Only once the basics are accounted for is it reasonable to assume it’s being caused by a buildup of microscopic particles.

Which brings us to the next question…

Does Your Filter Type Matter?

Yes, your filter matters. A lot.

The better your filter is at removing tiny particles, the less likely it is you’ll need to use clarifiers in the first place.

  • Sand filters are the least efficient, able to filter out particles as small as 20 microns in size.
  • Cartridge filters are considerably more efficient, able to capture particles as small as 10 microns.
  • DE filters (diatomaceous earth) are the gold standard, capable of removing particles as tiny as 1-2 microns.

Essentially, pool owners who use a sand filter are most likely to benefit from using clarifier, while those with a DE filter will have little use for it.

Note: If you have a sand filter, you can add some DE media to the filter in order to bolster its filtering capability. It won’t be quite as effective as a dedicated DE filter but it will certainly help.

Can You Swim After Using Clarifier?

Yes, it’s perfectly safe to swim after adding clarifier.

Clarifier is water soluble, low concentration, and non-reactive to chlorine, making it one of the safer pool chemicals to work with.

It’s worth noting that some clarifier manufacturers will direct you to wait 20 minutes or so for the substance to distribute throughout your pool, though this is usually just a formality.

The Bottom Line

Clarifier can be an effective pool maintenance tool, but it’s also a specialty chemical that should be reserved for special cases.

As long as your pool and its water are well maintained, chances are, you probably won’t need clarifier in 99% of cloudy water cases — especially if you have a DE or cartridge pool filter.

Categories: Pool Care, Pool Chemistry