All About Chlorine: How Much Pool Chlorine to Add and When

No matter what size or type of pool you have, it will always need a form of chlorine to stay clean. Chlorine is the main workhorse chemical that kills the bacteria that can turn your pool green or cloudy. The amount of chlorine each pool will need varies based on location, amount of sunlight received, nearby foliage, and frequency of usage. How much chlorine to add is also affected by the type of chlorine and the distribution method.

Here's what you need to know about pool chlorine, including how it works, the types of pool chlorine, and how much pool chlorine to add to keep your swimming hole clean and sparkling.

What Is Pool Chlorine?

Pool chlorine is used to disinfect water and keep pools clean and clear. When using chlorine for pools, it will generally be either in the form of a solid or liquid. However, in its natural state, chlorine is actually a yellow gas that is heavier than air. If left alone, chlorine tablets will emit a very strong odor that should not be inhaled. When chlorine is added to a pool, no matter what form it's in, it will immediately mix into the water and start cleaning.

Types of Pool Chlorine

There are four main types of chlorine for pools: chlorine tablets, chlorine liquid, chlorine from bromine, and chlorine from salt. All of these types are either chlorine based, another form of chlorine, or have chlorine extracted for use. Each form and type has their own advantages and disadvantages.

Chlorine tablets are great for general upkeep but not the best choice if you need to quickly raise the chlorine level of the pool. Shock in liquid form is better suited to quickly raising the chlorine level because of the speed and efficiency of mixing a liquid with a liquid. Bromine is a great alternative for people allergic to chlorine but is slightly weaker than and not as cost effective as chlorine tablets. Finally, salt is both cost effective and great for swimmers with chlorine allergies but requires additional machinery for chlorine generation, and it's more difficult to maintain proper chlorine levels.

How Much Pool Chlorine to Add

How much chlorine to add depends on the type you're using. But since tablets are the most common, we can say that the rule of thumb for how much chlorine to add is two 3-inch tablets per 10,000 gallons, or one 3-inch tablet per 5,000 gallons. The goal is to have a chlorine level at 1 to 3 parts per million (ppm). The packaging for your chlorine should explain how much to add to raise the level by 1 ppm in a 10,000-gallon pool.

Test your pool to find out its current level of chlorine, then add amounts of chlorine based on how many ppm you need to raise the level and how many gallons your pool is. Retest your water at least weekly and add chlorine as necessary.

3 Ways to Add Chlorine to Your Pool

Pool Float

A pool float is the most common way to add chlorine to a pool. Fill the float once a week with chlorine tablets and make sure the bottom vents are open to ensure proper mixing.

Chlorinator

A chlorinator automatically dispenses chlorine into your pool. To add chlorine this way, you'll turn the system off and isolate the chlorinator from system if possible. Remove the chlorinator lid and fill to the top with tablets. Put the cover back on, open valves, and adjust the control dial if needed. Make sure that the chlorinator is filled fully with water to avoid having any air pockets that will hinder the chlorination of the water.

Salt Cell or Chlorine Generator

Salt pools need salt and a salt cell or chlorine generator to operate properly. A salt cell only generates chlorine if the pool is running and there is an adequate level of salt. For this method you must test the water before making adjustments; it's possible that the generator is set correctly and there is not enough salt to extract chlorine from.

Chlorine Tablet Placement

Never add chlorine tablets to the skimmer mouth or basket. This increased concentration of
chlorine will make plastic brittle and crack over time and rot the internals of your filter system.

Chlorine vs. Pool Shock

Pool shock is a much stronger form of chlorine. Chlorine generally comes in either a powder or tablet form and is used for general upkeep. Pool shock can be in powder or liquid and, because of its potency, is used mostly for pool startup, closure, or when the chlorine level of a pool must be raised quickly, such as when your pool is green.

While you don’t need to (in theory) use shock for your pool, if you choose to use just chlorine tablets it will take much longer to clear a pool, especially when opening it at the beginning of the season. Ultimately, chlorine tablets are better for time release applications while shock is more of an instant option for immediate results.

Frequently Asked Questions

How much chlorine do I put in a 10,000 gallon pool?

In a 10,000-gallon pool you should add two 3-inch tablets.

How much chlorine do you add to a pool for the first time?

The first time you fill a pool you should add two 3-inch tablets for every 10,000 gallons. You may end up adding slightly more to account for the untreated water. After 24 hours, check chlorine level and add more if necessary.

Can you just add chlorine to a pool?

If it is set up for chlorine, yes, you can just add the chlorine to the pool, but test the water after 24 hours to understand how your pool behaves when chlorine is added. If you choose to use chlorine in a scenario where shock would normally be used, be prepared to have the chlorine take much longer to do the job of shock because of the comparatively slower release rate.