When choosing between liquid chlorine and chlorine tablets for your pool sanitation needs, the choice can be a bit confusing. Both products will chlorinate your pool, but is one a better choice than the other?
We dive in and find out.
Liquid chlorine is preferred over chlorine tablets by pool professionals however home swimming pools will benefit too. Liquid chlorine quickly raises or maintains chlorine levels without raising stabilizer. Chlorine tablets maintain chlorine levels and add stabilizer to the pool water.
In the rest of this article, we’ll take a closer look at what each product is, when it should be used and compare them directly to give you the full picture.
What is Liquid Chlorine?
Believe it or not, the bleach you use to clean your clothes at home is a form of liquid chlorine aka sodium hypochlorite.
Although it is a form of liquid chlorine, the type of liquid chlorine (liquid bleach) that you use in your pool is much stronger. Typically the bleach you use at home, like Clorox, contains no more than 7.5% chlorine while your pool chlorine contains 10% to 12% chlorine.
Further Reading: Can You Use Bleach or Clorox in a Pool? Is it Cheaper?
Liquid chlorine is comprised of chlorine, water and salt and poured directly into your pool. Because of its liquid nature, liquid chlorine is dissolved into your pool water in a matter of seconds.
To add it to the pool, you simply open a gallon of your liquid chlorine of choice and dump in the water. Pouring it in front of a jet is best to allow it to quickly spread throughout the pool.
Sounds easy enough, right? It’s not as simple as it sounds. Liquid chlorine can be tricky because it can be heavy to handle and you may need several gallons to get your free chlorine to the desired levels.
You can use a liquid chlorine like this one:
What is the Shelf Life of Liquid Chlorine?
Liquid chlorine doesn’t last very long and has a short shelf life of only a few weeks. After 6 months sitting in storage, the chlorine will be completely ineffective. For home use it’s best to buy it in small amounts otherwise you may find yourself making frequent trips to the pool store to empty your wallet.
Does Using Liquid Chlorine in a Pool Raise pH Level?
Liquid chlorine will raise the pH level of a pool as it has a pH of about 13. If your pH is already a little high, when using liquid chlorine, you will need to counteract that high pH with a pH decreaser like muriatic acid. About 1 quart of acid per gallon of liquid chlorine is needed to lower the pH.
Doing this will keep your pool’s pH in the desired 7.2-7.6 range.
You can use a pH decreasing product like this one:
Does Liquid Chlorine Contain Stabilizer (aka cyanuric acid)?
Liquid chlorine is an unstabilized chlorine and does not have any stabilizer (cyanuric acid or CYA) in it. This means that if used in a pool that is located outside and the water has no stabilizer or conditioner already in the water, the UV rays in the sun will degrade the chlorine in about 9 hours.
This would mean you would need to add more liquid chlorine manually to your pool after each full day of sun. Obviously this isn’t ideal for practical reasons or for your wallet. That’s a lot of trips to the pool store.
The solution is to make sure you either add a stabilizer like cyanuric acid or in addition to using liquid chlorine you use a stabilized chlorine tablet like Dichlor or Trichlor.
If your knowledge on pool stabilizer is a little lacking, you can read our article here.
If you use liquid chlorine you’ll need to add a stabilizer like this one:
Liquid Chlorine Uses
Liquid chlorine is best used in indoor pools, outdoor pools and commercial swimming pools.
Liquid chlorine can be great for pools BECAUSE it has no stabilizer and it doesn’t leave any residues or other chemicals behind. Without added stabilizer (CYA), liquid chlorine simply raises chlorine levels without increased CYA levels. That’s a big advantage if you have high levels of CYA in your water already.
Although other chlorines like Calcium Hypochlorite (commonly called pool shock or cal-hypo) are cheaper, cal-hypo will leave behind calcium carbonate when it reacts and dissolves. Calcium carbonate can bond to filters and is known to shorten their lives. It will also raise the calcium levels in the pool which may not be ideal.
That’s why liquid chlorine is also a preferred choice among commercial pool operators and pool professionals. It gives a high degree of control over the pool chemistry without side effects.
And it can easily be poured into the pool at the end of the day to get it ready for the next crowd of swimmers. There’s no waiting time for it to dissolve. Its low cost is a benefit for commercial pool operators as well.
Liquid chlorine is also a common choice for pool owners who need to shock their pool, although it’s expensive. Typically done when the sun goes down, a few gallons of liquid chlorine can be used to shock a pool quickly and easily without raising CYA or stabilizer levels.
Liquid chlorine is best added at night so that the sun doesn’t degrade the chlorine before it has a chance to work or mix in with the stabilizer. The pool filter should be run overnight to aid mixing if this method is used.
How Much Liquid Chlorine Do I Need?
The amount of chlorine that you’ll need to sanitize your pool is largely dependent on the size of your pool and the strength of the chlorine. The bigger the pool, the more liquid chlorine you’ll need to keep it between 1-3 ppm.
When looking to add 1 ppm of liquid chlorine to your pool, some simple math will be needed. If your chlorine level is already 2 ppm and you want to raise it to 3 ppm and you have a 10,000 gallon pool, you will need to add about 11 ounces of 12.5% liquid chlorine to raise the chlorine levels 0.6-1 ppm.
Using this math you can calculate the amount needed if you have a larger pool. For instance, if you own a 20,000 gallon pool, simply double what we already calculated and add 22 ounces of liquid chlorine to raise it 0.6-1 ppm.
Liquid Chlorine Need
|Raise Chlorine By||Liquid Chlorine Needed (6.5% strength)||Liquid Chlorine Needed (11.5% strength)||Liquid Chlorine Needed (12.5% strength)|
|1 ppm||19 oz||11 oz||10 oz|
|2 ppm||38 oz||22 oz||20 oz|
|3 ppm||57 oz||33 oz||30 oz|
|4 ppm||76 oz||44 oz||40 oz|
|5 ppm||95 oz||55 oz||50 oz|
|10 ppm||1.5 gal||1 gal||0.8 gal|
|20 ppm||3 gal||1.7 gal||1.5 gal|
|30 ppm||4.5 gal||2.6 gal||2.3 gal|
|40 ppm||6 gal||3.5 gal||3 gal|
What are Chlorine Tablets
Chlorine tablets are another way to chlorinate your pool and require a little less leg work than liquid chlorine. Chlorine tablets typically come in sizes of 1 or 3 inches. They are usually added to your pool through a floating chlorinator that sits in your pool water.
Don’t add them to the skimmer. It will create highly acidic water and could degrade the components in the skimmer and pump.
One-inch tablets are great for small pools of less than 5,000 gallons. One-inch tablets have a faster dissolving rate than three-inch tablets and can boost the chlorine quicker.
Three-inch tablets are great for outdoor pools greater than 5,000 gallons. In fact, one three-inch tablet can treat a 5,000 gallon pool on its own. Larger pools will use around three tablets at once and dissolve much slower making it the perfect choice for many pool owners.
Over time, the tablets slowly dissolve into the water and will maintain your desired chlorine levels. The floating chlorinators can be set to allow a certain amount of water in. This gives some degree of control for you to set your desired free chlorine level.
You can use a chlorine tablets like these ones:
Do Chlorine Tablets Contain Stabilizer?
Chlorine tablets like Trichlor and Dichlor typically have up to 50% stabilizer in them. Stabilizer is used to protect the chlorine from the sun’s UV rays. Stabilizer in chlorine tablets comes in the form of cyanuric acid (CYA). Without CYA, the sun will make your chlorine ineffective in a matter of hours.
It is important to know that while outdoor pools do need cyanuric acid, too much will actually make your chlorine ineffective. So, if your pool already has high CYA levels, it might be a good idea to use a chlorine that contains no stabilizer, such as liquid chlorine, until your CYA levels drop.
Chlorine Tablets Strength
Chlorine tablets, like Trichlor, can contain 90% available chlorine. It’s powerful stuff. This is a massive increase from the 12% of liquid chlorine.
With such a high amount of available chlorine, you are able to use less of it than you would with other types of chlorine. In addition to this, chlorine tablets are self-maintaining. This means it is a set it and forget it method. Once you add your tablets to your pool, you typically won’t have to add more for at least a week.
These sorts of chlorine tablets aren’t suitable for vinyl or fibreglass pools though.
Chlorine Tablet Uses
Chlorine tablets are a crowd favorite among residential outdoor pool owners. Already containing stabilizer is a great benefit that allows pool owners to sanitize their pool without the worry of the sun degrading their chlorine or having to add stabilizer separately.
They also store well and have a long shelf life.
They are also suitable to use in a floater or automatic chlorinator which can help reduce the amount of work to maintain your pool.
Can You Use Chlorine Tablets to Shock a Pool
Chlorine tablets are not suitable for shocking a swimming pool. They are too slow to dissolve and will not raise the chlorine levels high enough and fast enough. Plus given they have stabilizer in them, your stabilizer levels will shoot through the roof.
Cal-hypo or liquid chlorine is a much better choice for shocking. Although liquid chlorine is an expensive choice.
How Many Chlorine Tablets Do I need?
Most pool owners will need about 1-3 chlorine tablets a week to maintain a chlorine level of 1-3 ppm.
If you are looking to raise your chlorine ppm by 1, it is a little trickier than liquid chlorine because of its slow to dissolve nature.
However, on average if you were looking to increase your chlorine by 1 ppm and you owned a 10,000 gallon pool, you would need about 1.44 ounces of a three-inch tablet.
Keep in mind one three-inch tablet weighs about 8 ounces. However, a one-inch tablet weighs only 0.5 ounces. Using these weights, three one-inch tablets would raise your free chlorine levels about 1 ppm if you owned a 10,000 gallon pool.
But it would take some time as the tablets are slow to dissolve.
Liquid Chlorine vs Chlorine Tablets
Liquid chlorine and chlorine tablets are both used for chlorinating pools. Each of them has their pros and cons and are designed in different situations and circumstances.
Chlorine tablets contain stabilizer making them perfect for use in outdoor pools where the sun’s UV rays can deteriorate the chlorine. On the other hand, liquid chlorine contains no stabilizer making it better to maintain your chlorine levels if you already have stabilizer in the water or you have an indoor pool that does not get sunlight.
Chlorine tablets take days to be completely used up meaning that they are not good for quickly raising your chlorine levels. Liquid chlorine must be manually added, and often, when you need to bring your chlorine levels up. This can be costly and time consuming.
When comparing the amount of liquid chlorine to the amount of chlorine tablets, two three-inch tablets is going to equal one gallon of liquid chlorine. This is an important number to remember if you ever need to make a switch.
Check out the chart below for the full comparison of liquid chlorine versus chlorine tablets.
|Type||Liquid Chlorine||Chlorine Tablets|
|Uses||Indoor pools, outdoor pools, commercial pools, shock||Outdoor pools|
|Stabilizer||No stabilizer||Contains stabilizer|
|Rate of dissolve||Seconds||Days to a week, self-maintaining|
|Shelf life||Weeks||3-5 years|
|Price||Around $30 per gallon||$50 per 5 pound bucket|
Should I Use Liquid Chlorine or Tablets to Shock My Pool?
Liquid chlorine is a much better choice than tablets for shocking. It is going to go to work right away and get your chlorine levels high in a short time. Saying that, it is an expensive way to do it. Calcium Hypochlorite (cal-hypo) is a much more cost effective way.
Because chlorine tablets are slow releasing, they’re not very practical for shocking your pool. It would take a lot of tablets and a lot of time for your pool to reach a level that would work as a shock. In addition, with chlorine tablets containing stabilizer, your CYA levels in your pool would skyrocket if used as a shock.
Should You Use Liquid Chlorine or Tablets for Regular Chlorination of Your Pool?
For outdoor pools an ideal combination in the summer months is to use liquid chlorine along with 1 x 3” tablet per week. This will maintain the chlorine levels without raising the stabilizer levels too high.
I wouldn’t use chlorine tablets exclusively though as your stabilizer levels will get too high and you’ll need to drain your pool to remove it.
The amount of liquid chlorine and tablets you use will depend on the volume of your pool.
For indoor pools, stick with liquid chlorine or other unstabilized chlorine.
Congratulations, you are now an expert on liquid chlorine versus chlorine tablets and can confidently make the choice as to which one is right for you and your pool!
Knowing the ins and outs of each product is a major accomplishment and will help make your pool maintenance a breeze when it comes time to add your next dose of chlorine. If you ever feel like your chlorine isn’t performing as it should or is causing other side effects within your pool, refer back to this article to refresh your brain on why this might be occurring.
Happy pool operating!