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Chlorine vs Bleach for Pools: What’s the Difference?

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Maintaining a clean, clear, and sparkling pool all summer long is every pool owner’s dream. However, it can sometimes seem like an unwinnable battle between the elements and the sanitizer in your pool.

The two most commons cleansers of choice are bleach and chlorine to keep your pool free of bacteria and other organic invaders. But which is the best option? Before you add another chemical into your pool water, let’s take a look at the benefits and drawbacks of each. 

Ready to dive in?

The Cleaning Power of Chlorine and Bleach

Chlorine has long been the most common chemical used to sanitize pools. It’s potent, readily available, and trusted as a conventional cleaner for pools. While chlorine may be the go-to option for pools, however, bleach is the weapon of choice in the battle against germs inside the home. 

Bleach seems to do the trick when it comes to cleaning your countertops and bathrooms so why not your pool? 

Chlorine and bleach are very similar chemicals that both do a great job of fighting the good fight against a scummy, dirty, and murky pool. The main ingredient in bleach is, after all, chlorine so what’s the difference between the two?

A Clean Pool: Chlorine vs. Bleach

Typical pool chlorine is actually a chemical compound made up of 65% calcium hypochlorite with the remaining 35% made up of calcium and other inert ingredients. Household bleach, on the other hand, is usually only 6% chlorine and a different type at that. Bleach is composed of sodium hypochlorite, water, and a bit of salt to keep the chlorine gas in its liquid form.

Pool chlorine usually comes in a solid-state like tablets, powder, or granules, but can also come in liquid form as bleach does. Both chlorine (in any form) and bleach dissolve in water to release a hypochlorite ion. This little ion is a bit finicky, however, and will only transform into hypochlorous acid if the pH in your pool water is just right. 

Hypochlorous acid is the end goal here. This is the chemical responsible for disinfecting your pool through the process of oxidation, in which electrons are taken away from molecules. When hypochlorous acid oxidizes in your pool water, it kills germs and renders other nasty bacteria inert.

Effectiveness

It sounds like both chlorine and bleach end up forming the same cleaning chemical in the end. So how effective are they at their job?

The “bleaching action” of hypochlorite ion (and eventually, hypochlorous acid) is a hallmark of both chemicals and why they are both really good cleaning products in general. It turns out, however, that pool chlorine is substantially more powerful than household bleach for several reasons.

Free Available Chlorine (FAC)

One important difference is the concentration of free available chlorine (FAC) in each chemical. 

Studies have shown that if you dissolve 1 gram of chlorine in a liter of water, you’ll get an FAC level of 0.47 grams per liter. If you do the same with bleach, however, you’re FAC level is closer to 0.04. 

This significant difference shows that chlorine (calcium hypochlorite) has 11 times the free available chlorine of bleach, which translates into more sanitizing power per dose for chlorine. It also means that if you’re using bleach, you’re going to have to add a lot more to get the same result.

Bang for Your Buck

So I have to use more bleach than chlorine to get the same effect, right? I guess the price of each would end up evening out in the long run then?

Actually, no. Bleach is such a ubiquitous product with a long shelf life and a very low price tag. Bleach costs roughly $1-3 per gallon (a gallon is 8.35 pounds) in any grocery store, which comes out to $0.35 per pound (on the higher end). 

A large, 8-pound tub of chlorine granules or powder can cost around $55, which comes out to around $6.50 per pound. Meanwhile, one gallon of liquid pool chlorine will set you back about $30.

So even while adding 11 times more bleach to your pool to provide the same amount of free available chlorine as, well, chlorine — you’ll probably end up spending less on bleach than you would on chlorine in the long run.

Convenience

We’ve determined that bleach is weaker, so you’ll need to have more on-hand at all times to do the same work as less chlorine. You can, however, find bleach for a much cheaper price at more local stores nearby, without having to order online or go to specialty pool supply shops.

Bleach is also a bit more convenient in that it doesn’t need to be mixed or added in any specific way, as chlorine does. The exception here is liquid chlorine. With either bleach or liquid chlorine, you can simply add them to your pool’s skimmer and wait, running your pump while it goes to work.

Chlorine, on the other hand, should usually be pre-mixed in a bucket, diluted with water, and then poured evenly around your pool. This helps to protect you from potential splash-back, allow the chlorine to dissolve, and spread the chlorine more uniformly throughout your pool.

How to Use Bleach in Your Pool

The rule of thumb for using bleach to sanitize your pool is to use 1 gallon for every ¾ pounds of chlorine you might normally use. This translates to 2 gallons of bleach for an average-sized, 30,000-gallon pool.

Always use caution when adding bleach to your pool, as splash-back is still a safety concern with even this less-potent chemical.

How to Use Chlorine in Your Pool

If you decide to use traditional chlorine, however, for the same 30,000-gallon pool, you’ll need 1.5 pounds of solid chlorine (tablets, powder, or granules) to thoroughly cleanse your pool. 

If you’re using liquid chlorine, it will take between 150 and 300 ounces in a 30,000-gallon pool, depending on how much you need to increase your levels. This equates to between 1 and 2 gallons of liquid chlorine (or more) when adjusted for the size of your pool. 

Once you’ve diluted your chlorine of choice in a bucket of water, make sure to let it sit for an hour before adding it to your pool. This will give it a chance to fully dissolve and work its magic when you do add it to the water.

Remember too, that chlorine loses much of its cleaning power when used in the sunlight, so it’s always a good idea to add chlorine to your pool at night.

Which is Best?

It seems pretty clear that chlorine provides a better bang for your buck when it comes to cleaning power and overall effectiveness in your pool. If price-point is your main concern then sanitizing with bleach may be your best bet. 

The effectiveness and overall strength of traditional chlorine, however, can’t be ignored. For less of the stuff, you’ll get the same amount of cleaning power. 

In the end, it all comes down to personal preference and as long as you are testing frequently and topping up when needed, you’ll have a sparkling clean pool for you and your family to enjoy together.

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