Chlorine usage in a pool increases based on a number of factors some of which are environmental and many of which relate to the actual pool usage.
Chlorine gets used in your salt water pool through regular swimming usage by humans and animals as well as environmental factors such as direct sunlight and rain. Chlorine dies quickly in direct sunlight and higher temperatures increase the need for chlorinated water as does heavy rainfall.
Here are 15 factors that suck chlorine from your salt water pool and need to be accounted for.
1. Improperly balanced pool water
Balancing your pool water is particularly important as throwing one element out of range can effect chlorine and cause a chain reaction. A pH reading over 8.0 for example reduces chlorine’s effectiveness in your pool.
If inadequate chlorine is produced, algae can grow which means the use of a chemical such as algaecide and as that is happening, other bacteria can grow and throw other water readings out of whack.
While a salt water pool generally makes keeping water balancing easier than other pool types, sometimes events occur that cause pool readings to change. Regularly testing your water yourself with test strips and taking water samples to your pool company every few weeks during the pool season helps to ensure problems get caught early.
Check out my salt water pool chemicals chart to learn more about water balancing.
2. Size of the swimming pool
The bigger the pool (the more water you have) the more chlorine is required. That’s true of any pool. Sanitizing a large pool requires more chemicals and salt than a smaller one because there is more water to keep clean.
Ensuring you have a properly sized chlorinator is your first step to get things right. Getting a salt cell and chlorinator system that struggles to produce enough chlorine can be a big problem unless you’re willing to run your pump for more than the standard 8 hours per day with the chlorinator setting higher than the usual 50%.
3. Pool usage and frequency
The more you use the pool, the more chlorine you will need. Humans bring various contaminants into the pool and most notably sweat, urine, lotions, deodorants, colognes or perfumes, skin moisturizers, body oil and more. The more contaminants you bring into the water, the more chlorine gets used to keep the pool water clean and sterile.
Pool usage is of course a natural and expected part of pool ownership. From time to time you may have to use your Super Chlorinate feature (or shock the pool in the absence of that feature) or increase pump run time and the chlorinator run % setting to produce more chlorine during periods of heavy pool usage.
4. Children who use the pool
When children use your pool, the likelihood of them peeing in the pool and otherwise soiling or contaminating it increases. They may throw their dirty toys and food into the pool which also increases chlorine requirements.
The more young children who use the pool, the more chlorine you will require. Using the Super Chlorinate feature before pool parties and things of that nature is a smart idea.
And if your dog jumps in your salt water pool? That causes a whole new world of potential trouble and we’ll also talk about that below.
5. Maximum temperature that you experience
The higher the temperatures you experience the more chlorine is required. Warmer weather tends to help bacteria grow which in turn leads to a greater use of the pool’s chlorine. And of course the warmer the weather, the more you tend to use your pool.
Using your pool heater to increase pool temperature can also increase chlorine usage since you are artificially increasing the heat inside the pool which again, increases chlorine requirements.
NOTE: If you leave a solar blanket on for more than about 2 days straight during periods of strong sunlight, it has the effect of accelerating algae growth if you already have some in your pool so taking your solar cover off every few days is important.
6. Amount of direct sunlight that you experience
Sunlight kills chlorine which is why adding a stabilizer to the pool is an important protection as it basically acts like a sunscreen. It’s often said that strong sunlight in only 2 hours can kill off up to 90% of the chlorine in a pool. Add swimmers and other contaminating factors into your pool and you can see where chlorine gets used up and why pool water often gets cloudy, seemingly for no good reason.
Using the Super Chlorinate feature of your chlorinator on a weekly basis helps to bump up chlorine to account for extra sun and other chlorine-sapping environmental factors. If you don’t have a Super Chlorinate feature, you can extend the time that your chlorinator runs or turn the percentage running time up.
NOTE: The more you use your salt cell, the quicker it will need to be replaced. It has a lifespan usually measured in the total amount of chlorine it can produce.
Alternatively you can use pool shock if you have some handy. It’s fine to use chemical chlorine in your salt water pool as required.
7. Lack of stabilizer
Related to direct sunlight, adding stabilizer (also known as cyanuric acid or CYA) to your pool is a requirement to help protect the chlorine. The UV rays from the sun are very damaging and evaporate chlorine. Liquid and granulated pool chlorine products often have stabilizer added to them but since salt water pools don’t use chlorine in the same way, pool owners are required to add CYA manually from time to time.
If you fail to add any stabilizer or use a lower than required amount, your chlorine will die quicker in sunny weather and your chlorine requirements will increase.
The ideal CYA range in your pool is 60 ppm – 80 ppm and your pool company can test for it when you bring them a water sample.
Click here to learn more about stabilizer as it’s a critically important part of healthy salt water pool water chemistry.
8. Rainfall in your local area
The more rain you have, the more diluted your water becomes. Heavy rainfalls can really effect a salt water pool’s balance and knock it off significantly.
Depending on where you live, rain can be acidic which tends to reduce the pH of your pool making the water more acidic. So on the one hand more water in the pool requires more chlorine. On the hand the acidic nature of rain water lowers the pH which can cause burning eyes and itchy skin for humans while also cloudy water and staining of the pool vinyl in more severe cases. This in turn leads to a greater chlorine requirement, too.
If you’re expecting heavy rainfall, get ready to drain pool water if necessary and then Super Chlorinate to bring the (undoubtedly lower) chlorine levels back up again.
9. Shallow areas in the pool
Water is often noticeably warmer in shallow pool areas than deep areas because of course the sun doesn’t have to penetrate as deep to heat it up. If you have larger shallow areas than deep parts or if you have a shallow, non-diving pool, your chlorine requirements may be higher than a larger pool if the water temperature is higher.
The deeper your pool water on average, the more protected it is from the sun. The shallower the water, the more heat it experiences and the greater the chlorine needed.
10. Vegetation and gardens nearby
The more plants, leaves, trees, soil, twigs and other debris that can enter the pool, the more chlorine you will need. Rotting leaves and other dead vegetation should be removed from the pool as quickly as possible as should soil that has fallen in as the more it deteriorates the harder it is to vacuum and the more likely it will cause algae.
Colored leaves can also stain the pool liner which can be difficult to get rid of. Skimming and vacuuming your pool regularly as required will help to keep it clean of rotting vegetation.
11. Exposure to fertilizers
Fertilizer is a major cause of phosphates in a pool and not just your own. If your neighbors are using fertilizers or have their lawn sprayed for weeds, wind can send some of it into your backyard and into your pool water. Some pool products such as stain and scale removers may also contain phosphates.
Phosphates also enter the pool from swimmers who track detergent from their swimming clothes and towels in the water as well as sweat and other bodily fluids and skincare products. Aforementioned organic matter like leaves, twigs and soil that has phosphates can also make their way into the pool.
Your local water supply may also be a culprit: Some town water supplies have higher phosphates levels than others. If you live near a water treatment plant or agricultural area, your exposure may be higher.
Phosphates can be a big problem that you might have to deal with at some point in your salt water pool. The best level of phosphates in your pool is 0 but if you start to notice a fuzzy, lack of clearness on the surface of the water, it could be phosphates. Phosphates feed algae so that creates a secondary problem in the water if you don’t clear it up quickly enough.
If you have phosphates and/or algae, use an algaecide to get rid of the algae. Most times pool owners who keep their chlorine levels right don’t need to worry about phosphate levels.
12. Dirt that gets tracked into the pool
Dirt can be tracked into the pool in a number of ways. Whether unwashed swimming trunks, dirty feet, jumping into the water with street clothes, or dogs jumping in the pool there are many ways for dirt to enter the water.
If you have a garden nearby, wind can blow soil into the water.
If you have interlocking bricks or a sandbox nearby, sand can easily get into the water through rain and wind.
Minimize the dirt you bring into a pool by having people wear clean swimming clothes and having a shower before entering the water.
A good pool filtration system helps to keep the pool clean. Check out my options for pool filters by clicking here.
13. Dust that gets blown into the pool
Heavy winds can blow all sorts of debris into your pool. Dust is always in the air and although it often can’t be seen, you might notice from one day to the next small piles of dirt pooling in various parts of the pool water on the floor.
Depending on the type of filter you use, some simply aren’t good enough to draw out smaller particles and not allow them back into the pool water. Once a filter is past its best by date, you might need to invest in new filter mediums if your pool isn’t capable of handling smaller debris.
14. Pets or other animals
If you have a dog or other animal that swims in your pool, it does tend to bring more contaminants into your pool than an average person, not to mention fur and dander, all of which impacts your chlorine requirements.
Birds flying overhead can use your pool as a toilet and might even land in the pool and use it as a bird bath. Small rodents, worms and other critters can fall in the pool and if they die, they begin to rot and decay which adds to the chlorine usage and mess.
Dead animals should be removed from the pool as quickly as possible. Adding bird feeders or otherwise attracting birds to your home can negatively impact your pool.
15. Proximity of farms near your home
A farm, orchard or ranch that might be many miles away could use a wide variety of chemicals that end up making their way into your pool water. Pesticides, herbicides, fungicides, insecticides, and fertilizers are commonly used and many can have negative effects on your pool. Wind can make these travel a fair distance and the use of plows, spreaders, tillers and other farm equipment can cause more dust and contaminants to find their way into your backyard.
While there isn’t much you can do about this sort of concern, it’s something to be aware of anyways.
Summary
There are many human and environmental reasons that pool chlorine requirements increase over time. While many are simply unavoidable, others can be eliminated or at least reduced with some care.
The important part is to regularly test your salt water pool and keep water balanced. Maintain a chlorine level in your pool of 1 ppm – 3 ppm at all times.
Learn more about picking the right chlorinator for your salt water pool to ensure you choose one that meets your needs.