For a quick decision, look at the label for the active ingredient. It will commonly contain either calcium, dichloro, or trichloro.
Calcium stabilized chlorine will increase your water calcium hardness each time it is used, while dichloro and trichloro will increase the cyanuric acid (stabilizer) in your water.
Choose based on what is easiest for you to manage and what your water does not have too much of.
- Tablets contain trichloro and provide slow dissolving
- Granular types can contain calcium, dichloro, or trichloro types and dissolve relatively quickly
Deeper Dive
The simplest way to decide between using granular, tablets, or liquid chlorine is by examining two points:
- Understanding what else is being added to your water by using certain types of chlorine products
- How quick does your pool need chlorine: now, over the next few days, etc.
The first point is broken up into 4 common groups. In the table below, there is an at a glance look at the groups, what each add to the water, and some deciding factors.
| Major Chlorine Group | Common names | What else is being added to your water? | When do you need chlorine? |
| Sodium hypochlorite | Liquid shock, liquid chlorine, bleach, pool shock | Minor pH rise | Now or regular upkeep |
| Calcium hypochlorite |
Pool shock, chlorinating shock, power powder, cal-hypo |
Raises calcium hardness | Now or regular upkeep |
| Sodium Dichloro-s-triazinetrione |
Quick dissolve shock, chlor brite, dichlor |
Raises cyanuric acid (stabilizer) levels | Now or regular upkeep |
| Sodium Trichloro-s-triazinetrione |
Jumbo tabs, chlorinating tablets, chlorine puck, trichlor |
Raises cyanuric acid (stabilizer) levels | Over time or regular upkeep |
There is a fifth type, lithium hypochlorite, which adds practically nothing other than chlorine to your water. However, it is not commonly used due to much higher cost.