Saltwater pools are a great way to reduce your time and money when it comes to pool maintenance, and have become increasingly popular in recent years. But is pool salt special in some way, or can you use any salt in a salt water pool?
Today, I’ll break down everything you need to know about pool salt, how it works, and which type you should be using in your pool.
What Is Pool Salt, Exactly?
Pool salt is regular salt (NaCl) that has been specially prepared for use in pools and to work well with salt chlorine generators.
It’s special for 3 reasons:
- It’s especially pure, free of debris or organisms that can be hard on pool filters and equipment, and keep your water clean and clear.
- It’s a special grind that is not too coarse, so it dissolves quickly in water, but not too fine, so it works better in generators.
- It’s available in bulk, since you need a lot of salt to maintain the right salinity levels in a salt water pool.
In theory, you could use everyday table salt, but it likely won’t meet the criteria above, and many contain unwanted additives that will stain your pool. Since these additives aren’t always listed, it’s hardly worth the risk in most cases.
How Pool Salt Works
In a swimming pool with a salt chlorine generator, dissolved salt passes through the generator, which uses something called electrolysis to break the salt molecule down into smaller molecules.
Salt (NaCl) is formed when sodium bonds with chloride. When that bond is broken, you end up chlorine and sodium hydroxide, both of which are effective cleaning agents.
By breaking salt into smaller molecules, a salt chlorine generator uses simple pool salt to continually produce free available chlorine (chlorine that hasn’t been used up), as long as the water has enough salt for the generator to work correctly.
Why Pool Salt is Important
Pool salt is important for several reasons:
- Using the right pool salt helps a salt chlorine generator work efficiently.
- Maintaining the right salt levels helps to maintain the right chlorine levels, and therefore a clean pool.
- Low-quality pool salt can have mineral or organic contaminants that may cause stains, scaling, or cloudy water.
Different Kinds of Pool Salt
Solar salt is made when seawater is spread out on land, and allowed to dry. The water evaporates, leaving the salt behind. In many cases, the dried salt is simply packaged and sold; sometimes it is further refined by being washed or ground.
Unfortunately, because the ocean is full of tiny organisms like brine shrimp, and is also high in other minerals, the solar salt evaporation process also leaves behind a lot of dead microorganisms and bacteria that are hard on pool filters and your salt chlorine generator.
Mechanically evaporated Salt
Mechanically evaporated salt is also made from seawater, but it is mechanically heated rather than evaporating in the sun. Because the heat levels are mechanically controlled, they can be more accurate, and more effective at killing bacteria.
While this method does kill bacteria and microorganisms, it also creates a very mineral-rich salt, that has pure salt mixed with calcium, magnesium, copper, nitrites, and other minerals.
This mineral-rich salt can create “hard” water, where minerals build up on pool surfaces, cause staining, and make your filter work harder. They also make it more difficult to control the chemical balance of your pool water.
Mined salt is dug out of the earth, like the rock salt most people are familiar with. It’s pure salt, with no biological contaminants, and few extra minerals, averaging 95-99% pure sodium chloride.
Because of its purity and freedom from contaminants, mined salt is considered the best source for use in pools.
Regardless of the methods used to produce the salt, it is always best to use salt that is packaged and labeled for use in a pool.
What To Look for when Buying Pool Salt
These days, you have a lot of options when it comes to pool salt. Here are the key features to look for:
- Purity. Pool salt should be at least 99% pure. The presence of other minerals can cause staining, or scaling, and at the very least requires that a salt chlorine generator be cleaned more often. Choose the purest salt you can buy.
- Even granulation and coloring. Look for “food grade” salt that looks almost like table salt, with pure white, evenly-sized granules. Fine crystals dissolve more quickly and evenly, without collecting on the top or bottom of the water, where it may stain or simply not reach the generator. An irregular color or shape is often an indicator of impurities.
- Additive-free. While some pool salts advertise anti-clumping or anti-staining additives, it is best to avoid all additives, including iodine, in pool salt. Pure salt works best with a salt chlorine generator, and some additives make it more difficult to properly balance your pool.
While pool salt can be more expensive than other kinds of salt, the good news is that, once you have the right salinity levels in your pool, it doesn’t need ongoing adjustment.
The level of salt in a pool will remain fairly constant, only requiring adjustment when there has been a lot of rainfall or splashout that changes the dilution of salt in the water.
How to Add Salt to a Pool
Most salt water chlorinators require a salinity level of 2000 – 3500 ppm, but it’s important to check the recommendations on your particular model.
If you are adding salt to a pool for the first time, it is best to add a little less salt than you think you need, so that you can re-test and add more if needed. If you add too much, there is nothing to do but remove some water, add in new fresh water, and start over again.
To add salt to a pool, follow these steps:
- Balance the pool. It’s always best to balance your pool water before adjusting salinity. Follow your salt water generator’s guidelines for the optimum levels to balance to.
- Determine how much salt you need to add. You can consult this table here to figure out how many pounds of salt you need to reach your desired salinity.
- Check your salinity levels again. Before adding salt, check your salinity levels again. Salinity can be affected by temperature, so in particularly hot or cold weather, it is best to take a sample of your pool water indoors (or to a neutral area) and let it rest to reach room temperature before performing a test.
- Turn off your chlorine generator. Many salt chlorine generators will have a pump that keeps circulating water even when it isn’t generating chlorine, which will help your new salt disperse evenly.
- Add a little less salt than you think you need. Most people add salt by sprinkling it on their steps, and then brushing it into the water to help it dissolve evenly. With a combination of broadcasting a bit at a time, and using a brush to stir the water, help the salt dissolve into the pool water.
- Wait for 18-24 hours, and then re-test. In a large pool, it may take up to 48 hours for all the salt to completely dissolve and form a solution with the water. In warm weather, it will take a shorter amount of time. As a rule, wait for 24 hours, and then re-test your salinity to see if more salt is needed.
- If necessary, return to step 5 and repeat.
While pool salt is “just salt”, it’s also so much more than that.
Because the quality of the salt you use makes a huge difference in the life of your salt chlorine generator, and in your enjoyment of your pool, and because salt levels renew themselves, it’s best to just invest in the best possible pool salt you can get.
Now you know everything there is to know about your pool salt options, what to look for, and how to use it. Enjoy your saltwater pool even more with high quality pool salts.