The Short, Short Version
Chlorine levels should be tested at least twice per week. They should also be tested after heavy use or rainfall, as they are likely to be depleted.
Pool chlorine is responsible for sanitizing your pool and hot tub water to make it safe to swim. Therefore, there’s really no such thing as testing pool chlorine too frequently. The easiest way to check your chlorine levels is with test strips. Of course, constant testing is impractical. So, what is the minimum frequency pool chlorine should be tested to ensure free chlorine is at a safe level?
The answer to this question depends heavily on how often your pool is in use, who uses your pool, and weather events that may introduce a large amount of fresh water into your pool.
This article outlines common factors that affect how frequent you may want to test your pool chlorine. You may also be interested in learning How to Test, Raise, and Lower Pool Chlorine.
Factor #1: Regular Use
At a minimum, you should test your free chlorine 2 or 3 times per week during seasons of regular use. This works out to once every day or two. Testing at this frequency should ensure you are able to keep free chlorine levels at recommended ranges of 2.0 to 4.0+ ppm, assuming no unusual activity or events cause a spike in contaminants. We recommend testing and adding chemicals in the evenings, when there is no direct sunlight to expedite the interaction of free chlorine with the pool water. This will also help save on chemical costs.
Factor #2: Frequent Use
If you use your pool or hot tub more than once per day during swim season, you may want to increase your free chlorine testing frequency to 4 or 5 times per week. Perspiration contains bacteria that free chlorine will react with to sanitize your pool. The more you use your pool the more perspiration will enter your pool and more free chlorine will be used up. Increasing testing frequency is necessary to maintain goal ranges of free chlorine day to day. When your free chlorine levels get too low, we recommend using calcium hypochlorite to raise them back up.
Factor #3: Use by Pets and Small Children
If your pool is frequently used by small children or pets, you may want to test free chlorine more frequently than 2 or 3 times per week. Pet hair contains more bacteria and other contaminants than human hair and skin because pets typically bathe less frequently and get dirtier throughout the day. Pets and small children are also more likely to have bathroom accidents in the pool, including minor ones you may not notice.
Factor #4: Large Gatherings
It is a good idea to test chlorine before and after events that may affect their levels. One such event may be a gathering in which more people than usual use your pool. It’s a good idea to test your chlorine levels before and after this type of event for the same reasons it is a good idea to test if you use the pool more frequently. Perspiration and other contaminants will be introduced to your pool at a higher volume the more people use your pool.
Factor #5: Weather Related Events
Other events that may warrant more frequent testing are weather events. For example, a heavy rainstorm will introduce a lot of new fresh – and potentially acidic – water into your pool. This new water will dilute the concentration of free chlorine, so it is always a good idea to test your chlorine levels after such an event occurs.