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



Chlorine and bleach are sometimes used interchangeably in the pool business, but are they really the same thing?

In this article, you’ll learn the difference between chlorine and bleach, whether you can use bleach in a pool, and how to determine which one to use.

Quick answer: Bleach is just a weaker form of liquid chlorine. It shares the same active ingredient, sodium hypochlorite, and can be used in place of liquid chlorine assuming it doesn’t contain any additives.

Bleach = Liquid Chlorine

Household bleach is simply sodium hypochlorite (the active ingredient) mixed with lots of water, resulting in around 6% strength.

This happens to be the same active ingredient in liquid chlorine but with slightly less dilution for a more concentrated solution. It’s typically anywhere from 10% to 12.5% in strength, though it does exist in higher concentrations.

To clarify, the only real difference between them is concentration; chlorine is a strong bleach, and bleach is a weak chlorine.

But that begs the question…

Can You Use Bleach in a Pool?

Yes, you can use household bleach in a pool. It’s completely safe.

However, some bleach products contain additives that aren’t suitable for a swimming pool, such as fragrances and thickeners. These can cause foaming and other water quality issues, especially in large volumes.

Given the lower concentration of sodium hypochlorite, you’ll also need to use considerably more bleach than you would liquid chlorine to achieve the same sanitizing power.

For example, it would take roughly twice as much 6% bleach to achieve the same level of chlorination 12.5% liquid chlorine would provide.

Overall, while you can use household bleach to sanitize and even shock your pool, you’ll need to make sure it contains no additives and be prepared to buy a lot more of it than you’re probably used to.

Which Should You Use? (Bleach vs Chlorine)

You already know you can use bleach instead of chlorine, but that doesn’t necessarily mean you should.

Let’s weigh it all up:

1. Convenience

Household bleach is available on just about every street corner, making it the easy choice in a pinch.

Liquid chlorine can be a bit more difficult to find depending on your region, as stock is often limited to pool stores, home improvement stores, and some large department stores.

However, even though it’s generally harder to come by, liquid chlorine is easier to transport and store simply because much less of it is required due to having a higher concentration of sanitizer.

What’s more, handling/pouring your chlorine on a daily basis is more challenging when you’re having to deal with higher volumes of liquid, especially for those with physical ailments.

Verdict: Liquid chlorine can be more difficult to source but it’s also more convenient by every other measure. Unless you need chlorine in a hurry, stick with liquid.

2. Cost

On a gallon-for-gallon basis, bleach is often cheaper than liquid chlorine because it’s sold in much lower concentrations.

While this may seem attractive at first glance, the reduced strength has to be factored in when making a comparison to liquid chlorine — and the best choice isn’t always a given.

A lot of this depends on where you’re located, the brand you buy, the store you buy from, whether you buy in singles or in bulk, and any promotions that happen to be running at the time.

For example, you may personally be able to get 12.5% liquid chlorine for $5 per gallon, while 6% bleach is only slightly cheaper at $4 per gallon. In that case, liquid chlorine is the clear winner.

Meanwhile, someone else might find the same 12.5% liquid chlorine at $9 per gallon, while 6% bleach is only $3.50 per gallon. In that case, it would make more financial sense to buy twice as much bleach.

Verdict: If cost is a bigger factor than convenience, you’ll need to run the numbers based on local pricing. Household bleach may work out cheaper than liquid chlorine despite having to buy twice as much.

What About Other Forms of Chlorine?

Bleach and liquid chlorine are essentially the same thing in different concentrations, but neither is much like other forms of chlorine.

The active ingredient in granular and tablet chlorine—which can be trichlor, dichlor, or calcium hypochlorite—ranges from 48% to as much as 90% strength, and is usually dissolved in a bucket before use.

What’s more, trichlor and dichlor-based chlorine is stabilized, containing a high amount of cyanuric acid to protect it from breaking down in sunlight, while calcium hypochlorite contains calcium.

Both forms of chlorine will also significantly influence the pH level of your water (usually negatively), while bleach and liquid chlorine only marginally and temporarily raise your pH level.

Bleach and liquid chlorine are considerably weaker in comparison, but they’re the purest form of chlorine you can realistically buy for your pool.

The Bottom Line

Using bleach in your pool can be a scary concept until you realize it’s made of exactly the same stuff you already use.

Liquid chlorine—and by extension, bleach—will always be a solid option for pool sanitation, even above other forms of chlorine. Just make sure it’s additive-free and cost-effective and you can’t go wrong either way.

Categories: Pool Care, Pool Chemistry