There are five different types of chlorine: sodium hypochlorite, calcium hypochlorite, lithium hypochlorite, trichlor, and dichlor.
While they all increase free chlorine (FC) levels, understanding each type of chlorine is important as they offer unique benefits and drawbacks depending on your pool’s specific needs.
Chlorine falls into two categories, in the most basic sense: stabilized and unstabilized.
Stabilized Chlorine
Stabilized chlorine contains cyanuric acid (CYA). CYA does not break down in sunlight, so the chlorine will last longer in the pool, which allows you to add it less frequently.
Keep in mind, however, that too much CYA in the water can inhibit chlorine’s ability to both sanitize and oxidize, so make sure your CYA levels are not too high before using stabilized chlorine.
Unstabilized Chlorine
Unstabilized chlorine has no stabilizer added. This means that CYA needs to be added separately. Otherwise, unstabilized chlorine will break down faster by UV rays, forcing you to use more chlorine.
This further highlights the importance of having balanced water and enough stabilizers to control chlorine use.
The Different Types of Chlorine and Their Attributes
As mentioned above, there are five different types of chlorine that you can use to sanitize your swimming pool:
- Sodium hypochlorite (liquid chlorine or bleach)
- Calcium hypochlorite (cal hypo)
- Lithium hypochlorite
- Trichlor
- Dichlor
There is one additional chlorine form for pool owners with a saltwater pool. These pools transform salt into chlorine granules using a saltwater chlorine generator (SWG).
Listed below are the various forms of chlorine along with best practices for each.
Sodium Hypochlorite (Liquid Chlorine or Bleach)
Pros
Cons
Liquid chlorine is an unstabilized form of sanitation. Most know it simply as household bleach, but you want to avoid bleach products with scents, fabric enhancers, or other additives. Liquid chlorine can be found at most big box and home improvement stores and is a great way to sanitize your water.
It is typically the least expensive, but since it is unstabilized, it will burn off quicker, meaning more needs to be added frequently. However, since it doesn’t add any other chemicals to the pool it is the most recommended form for daily use.
How to Add Liquid Chlorine to Pool
Slowly pour the amount you need in the deep end close to a return jet. Dumping a full gallon shouldn’t take less than a minute.
Calcium Hypochlorite
Pros
Cons
Commonly referred to as cal-hypo, this is another unstabilized sanitizer that comes in powder form. You’ll be able to find cal-hypo in pool stores as well as some home improvement retailers. Some pool stores will sell cal-hypo as “shock”.
While cal-hypo will not add CYA to the water, it will raise calcium hardness (CH) over time. Too much CH can introduce scaling and cause the water to become cloudy. It is important to ensure CH levels are within range when using cal-hypo.
How to Add Calcium Hypochlorite to Pool
There are two general ways to add cal-hypo. The first way would be to broadcast the amount needed in the deep end. Most granules will dissolve before hitting the bottom of the pool. Use your pool brush to disperse the rest that lands at the bottom.
The other and more effective way would be to pre-dissolve the cal-hypo in a bucket of pool water, mixing it with a stick to ensure all granules are dissolved before dumping it into the water.
Lithium Hypochlorite
Pros
Cons
Like cal-hypo, lithium hypochlorite is an unstabilized sanitizer that comes in powder form. It can also be found in your local pool store and retailers. The most appealing aspect of lithium hypochlorite is its tendency to dissolve very quickly, so there is little risk of bleaching liners.
However, it is often a bit weaker than other chlorine and is quite expensive, making it a less popular choice for weekly sanitation.
How to Add Lithium Hypochlorite to Pool
Like cal-hypo, you can either broadcast it into the deep end and brush and granules that hit the bottom so they fully dissolve or pre-dissolve and mix it in a big bucket of water.
Trichlor
Pros
Cons
Trichlor is a stabilized sanitizer commonly referred to as tabs or pucks. When pool owners use floating devices, they use trichlor tabs.
Trichlor is the slowest form of chlorine to dissolve and gets dissipated over a longer period of time, making it less of a hassle when it comes to overall sanitation.
However, since it is stabilized, it will increase CYA over time. Additionally, trichlor will lower pH and total alkalinity (TA) since it contains acid.
How to Add Trichlor to Pool
Trichlor can be added through a pool floater.
Dichlor
Pros
Cons
The other stabilized sanitizer, dichlor, mostly comes in powder form but can also be found as tablets. Because it dissolves quickly, pool stores generally sell this as “shock.”
How to Add Dichlor to Pool
Dichlor in powder form can be pre-dissolved in a bucket of water before adding to the pool. If it is in a tab form, use your pool floater.
Salt Water Chlorine Generator (SWG)
Pros
Cons
Utilizing an SWG is another way to chlorinate your pool. It essentially converts salt in the pool to chlorine, making the sanitation process fairly easy.
However, you must purchase a fairly expensive saltwater generator to add to your plumbing equipment. Some may consider that too much and prefer to chlorinate in other ways.
How to Add Salt to Pool
Salt can be added by broadcasting it in the deep end. Any granules that reach the bottom can be brushed until fully dissolved.
Know Your Chlorine Usage
Knowing what each type of chlorine can potentially add to the pool is important. Water can get out of balance pretty quickly if left unchecked.
If you want to know how much chlorine you need to add to the pool, check out our chlorine calculator!
As always, make sure you are testing so you know not only how much FC is added but also the effects of other chemical levels.