Sodium Hypochlorite In Your Pool: Everything You Need To Know

Are you wondering about sodium hypochlorite and what it has to do with your swimming pool maintenance? Well, you’re in the right place!

Sodium hypochlorite is the main ingredient in household bleach as well as in some of the pool sanitizers you use. Most commonly, liquid chlorine is made of this compound. 

But a lot of the liquid chlorine you buy for pools contains calcium hypochlorite instead.

What Is Sodium Hypochlorite?

Scientifically speaking (and we all love it when I get all science-y), sodium hypochlorites are ions composed of oxygen and chlorine.

It has a naturally high pH level at 13 and it is very unstable so it is rarely used alone in pools.

Sodium hypochlorite only has about 5% available chlorine, so it’s not always the most effective pool sanitizer.

How Does Sodium Hypochlorite Work?

Basically, sodium hypochlorite “breaks down into many different chemicals” once it is added to the water.

Two of those chemicals are hypochlorous acid and hypochlorite ions, which both destroy bacteria and oxidize the water. 

How Is Sodium Hypochlorite Used In Pools?

Sodium hypochlorite, in its liquid chlorine state, is the simplest form of pool sanitizer in that it is already diluted appropriately and can be added straight to your pool water.

Most of the time, you’ll just pour the directed amount into your skimmer, and keep the pump running to distribute it.

Difference Between Sodium Hypochlorite And Calcium Hypochlorite

Both sodium hypochlorite and calcium hypochlorite are disinfectants, but the products are actually a little different.

Calcium hypochlorite, or cal-hypo, as it is often called, contains calcium, whereas sodium hypochlorite does not.

Cal-hypo is sold as either a solid or a pre-diluted liquid and is about 65% in chlorine strength. Because it contains calcium, though, pools in areas with very high calcium hardness levels and calcium scale tend to steer away from this product. 

Sodium hypochlorite, as mentioned, doesn’t contain near as much free chlorine, but it’s usually quite a bit cheaper to buy. 

It’s best to use in areas with hard water since it won’t add calcium, but if you have soft water, you’ll need to add calcium to the water anyway to raise those levels. 

Both products will do the job; the main difference is the amount you will have to add to keep your levels balanced. 

Cyanuric Acid

But because either of these types of chlorine is unstable, UV rays will quickly eat it up, rendering it useless in very little time.

And when I say very little time, we’re talking less than 20 minutes for half the chlorine to be gone!

That’s where cyanuric acid, or CYA, comes in.

This chlorine stabilizer bonds with the ions the chlorine breaks down into to keep them from breaking apart. So, in layman’s terms, it makes the chlorine last longer by protecting it from the sun. 

Most chlorine tablets you buy already have the proper amounts of CYA added to them, but if you’re using liquid chlorine, you’ll have to read the instructions well and make sure you’re adding it correctly. 

This is because too much of a good thing isn’t always a good thing: too much CYA can also block the chlorine’s effectiveness, often referred to as chlorine lock.

Chlorine lock means that your pool will test for proper amounts of chlorine. The problem is that it’s just not sanitizing the water.

The way to test for this is to test for both total chlorine and free chlorine using the best pool testing kits

If these two amounts are out of balance, you probably have chlorine lock and will need to take measures to correct it, usually by shocking your pool (readhow to shock a pool) with a non-chlorine shock.

Bottom Line

When buying disinfectant for your pool, you’ll probably most commonly see cal-hypo.

But if you live in a region where calcium deposits are an issue, sodium hypochlorite might be the more effective way to go.

Just make sure that you’re testing all your levels frequently and using it with a stabilizer like CYA. 

What type of disinfectant do you use in your pool?

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