What Type of Chlorine Should I Use In My Swimming Pool?

What is chlorine? It seems a pretty straightforward question with a fairly straightforward answer. Right? Yes, and at the same time, no. Chlorine is the most efficient and cost-effective method currently known to sanitize, disinfect, and oxidize the swimming pool water.

There are different types of chlorine. Gas (or elemental) chlorine is not really used anymore in pools. Liquid chlorine is used predominantly by service pros. Solids (granular and tablets) are used by homeowners and service pros alike.

If you really want to geek-out on this topic head over here for a really scientific approach to pool chlorination from the American Chemistry Council.

What is the difference between liquid and solid chlorine?

Liquid chlorine; also known as ‘sodium hypochlorite’ is most commonly used by pool pros. It’s cheap and easy to produce and dispense and immediately goes to work. Additionally, there are little to no byproducts that affect pool water chemistry adversely, for this reason, pros prefer to use liquid chlorine. Consumers can purchase liquid chlorine at many hardware stores where pools are common. Liquid chlorine is stable enough to store for a few weeks at a time, but many homeowners shy away from it due to the hazard potential and bulk of storage.

Solid chlorine granules or tablets are common due to longer shelf life and ease of storage. What is more, solid chlorine is also perceived to be safer to handle. Service pros often use solid chlorine sparingly due to the added expense and the fact that there are other both inert and active chemicals present in order to stabilize the chlorine in its solid-state. Most solid chlorine compounds are able to be used in floating dispensers and in-line feeders as tablets. Granules are typically broadcast across the surface of the pool or diluted in a bucket of water and then dispensed.

Can I Use Bleach as Chlorine In My Pool?

Technically, yes. But it’s going to cost you. Here’s why. The chlorine bleach found in your laundry room is the exact same chemical composition as liquid chlorine (except the kind with perfumes and such). Bleach costs about $3.50 per gallon. Your consumer bottle of liquid chlorine, like this HDX brand from Home Depot, will run you about $4.50/gallon. Seems like a good deal right? Just make a trip to the grocery store instead of the hardware store, right?

Well, not really. It’s all about what’s in the bottle. Typical bleach contains about 6% chlorine. While typical consumer-available chlorine is 10%. I won’t bore you with the math…mostly because I don’t want to make my head explode from doing it, but saving 33.5% per gallon for 40% less product doesn’t seem like a deal to me. So essentially the effectiveness of the bleach is much less than that of liquid chlorine, which means maintaining proper sanitizer levels becomes more difficult and more expensive.

What type of chlorine should I use in my swimming pool?

You may be sensing a leaning in this article toward liquid chlorine, and you would be right. Both in my experience and from a purely scientific standpoint, liquid chlorine is a better all-around way of sanitizing a pool, barring a few unique circumstances. There is more information in the solid chlorine category that adds a pretty large caveat to this discussion. If you use solid chlorine as a primary source sanitizer you’ll want to make sure are checking some other parameters such as calcium, iron, total alkalinity, and cyanuric acid. For the purposes of simplicity, however, we will just look at liquid vs. solid chlorine.

As a general rule, for regular chlorination, we say use liquid chlorine if it’s available to you and not cost-prohibitive. It’s about as pure as you can get without additives or ancillary chemistry issues, it’s affordable and easy to use. If liquid chlorine is not an option, or you have difficulty maintaining proper chlorine residual in your pool, try rotating through at least two of the other types of chlorine. Or supplement the liquid with some sort of solid, preferably ‘Sodium Dichlor’ tablets in a floater.

The many additives in solid chlorine can wreak havoc on the rest of your pool’s water chemistry balance. to the point that you may end up needing to partially drain or fully draining your pool to remove some of the additives. I had a pool customer that used exclusively for years dichlor tablets. His cyanuric acid levels were off the charts. I don’t care how much cyanuric neutralizer you try to use, it only works under perfect circumstances so there’s no way to lower it. You may be wondering, whats cyanuric acid and why is that so bad?

Well, stay tuned for our next article, we will cover just that…