Pool ownership is a luxury that comes with the headache of maintenance. Maintaining the pool is important to one’s health and the pool’s life, and chlorinating the pool is no exception. If you are a brand new pool owner, you may question exactly how much chlorine is needed for your pool.
A pool requires between one to three parts per million (ppm) chlorine for every 5,000 gallons of water in your pool. The amount of chlorine that you use will vary per manufacturer, but the most common form, a three-inch tablet, will be needed for every 5,000 gallons of water in your pool to raise it by one ppm.
There are many brands and compounds of chlorine on the market, and this variety can quickly overwhelm a new pool owner. This article will explain the basics of what chlorines you are likely to use in your pool and guide you through adding chlorine to your pool in an easy step-by-step.
What Exactly is Chlorine?
When pool owners refer to chlorine, they are referring to a chlorine compound – either sodium hypochlorite or calcium hypochlorite – used to kill the bacteria and viruses in a pool. Chlorine is an effective and inexpensive sanitizer and is used by most pool owners to keep their pools free of contamination.
Chlorine is typically found in solid granular or tablet forms (sodium hypochlorite), or in liquid form (calcium hypochlorite). It works very well in water with a pH between 7.2 and 7.6, though it is sensitive to changes in the pool’s chemistry that take it above this pH. It is also sensitive to sunlight and often contains ‘stabilizers’ to block the effects of UV radiation.
While there are several options in the types of chlorine you can purchase, they will all work regardless of the type of pool you have. That said, a pool’s chemistry is difficult to manage.
Organic matter, temperature, rain, sunlight, and other factors can change the pH levels of the cool and cause different reactions with the chemicals in the water. This includes chlorine, so while any chlorine may work for the purpose of killing bacteria in your pool, you should select carefully based on your needs.
What Type of Chlorine Should You Use?
The most common type of chlorine used is calcium hypochlorite due to its low cost, ease of use, and rate of dispersal. There are other considerations that may change which chlorine you use for your pool, however.
Firstly, pool chlorine falls into two general categories: stabilized and unstabilized. Stabilized chlorine has cyanuric acid or other additives added to it that acts in a way that protects the chlorine from the effects of the sun. Unstabilized chlorine does not have this ability and can only be used at night or indoors.
There are two types of stabilized chlorine: Sodium dichlor and trichlor. Sodium dichlor helps control the pH levels and can kill black algae. Trichlor is often used in hot tubs due to its resistance to high temperatures.
The main downside of using stabilized chlorine is the cyanuric acid that stabilizes it. High levels of this can reduce the effectiveness of the chlorine and eventually cloudy up your pool water.
Of the unstable chlorines, the most popular by far is calcium hypochlorite. It is inexpensive and effective, but it will slowly add calcium to your pool.
Lithium hypochlorite is an alternative to calcium hypochlorite that is free of calcium buildup and requires no dissolving beforehand. However, it is more costly.
How To Know How Much Chlorine To Use?
In general, you will want to use one three-inch chlorine tablet or 26 – 52 oz of liquid chlorine for every 5,000 gallons of water in your pool. The amount that you will need to use for the type of chlorine you buy will be shown to you on the product’s label under the directions describing its use.
If you are not sure how many gallons your pool contains, there is a very simple math equation you can follow. Measure the length, width, and average depth in feet of your pool, then multiply by 7.5 to get gallons. If your pool has a slope, take the depth of your pool at the shallowest point and the deepest point, then divide that figure by two to get a rough average.
Pool size (5-foot depth)
|Recommended Chlorine Use|
|Liquid Chlorine||Chlorine tablets|
|Hot Tub||Not recommended||1-5 tablets (1 inch)|
|12 ft Round Above-Ground||26 – 52 oz||1 tablet (3 inches)|
|15×24 ft Oval Above Ground||52 – 104 oz||2 tablets (3 inches)|
|12×24 ft Inground||52 – 104 oz||2 tablets (3 inches)|
|16×34 ft Inground||104 – 208 oz||4 tablets (3 inches)|
|24×44 ft Inground||208 – 416 oz||8 tablets (3 inches)|
How to Chlorinate a Pool?
If you have a basic understanding of the chemistry involved with adding chlorine to your pool (or can read the manufacturer’s directions), then chlorinating your pool simply requires you to test the water, add the chlorine, let it sit, then test it again. What you need is a test kit, safety equipment (goggles and gloves), a 5-gallon bucket, and a measuring cup.
Step 1: Test the Water
In order to get started, you need to know how much chlorine you will need to add. To do this, you need to test the water and determine its current pH and chemical levels.
There will be different chlorine readings on your test kit. It will show you free chlorine, which is the chlorine in the water that is actively disinfecting it, and the combined chlorine, or the amount of chlorine that has already been used up. Free chlorine needs to be between 1 and 3 parts per million (ppm), and the combined chlorine should be less than 0.2 ppm.
Step 2: Calculate How Many Chemicals You’ll Need
The manufacturer of the chlorine will tell you how much chlorine you need to add to your pool. For their recommendations, round up your pool’s gallon capacity to the nearest 5,000 gallons. This will ensure that you are covered for the amount of chlorine you will need to add to the pool.
If you are using three-inch tablets, remember that one tablet is needed to raise the chlorine level in 5,000 gallons of water by one ppm. This means that if your pool is 24,000 gallons with a current free chlorine reading of one ppm, you will need to add five tablets to raise it to two ppm.
Step 3: Mix Chlorine With Water
If you have granular chlorine or your chlorine requires pre-mixing, you will have to mix it with water prior to putting the chemicals in the pool. For this purpose, find a five-gallon plastic bucket and use it to dissolve the chlorine that you will need to use in your pool. Note that some chlorines, such as liquid chlorine, will not require a mix, but you may want to measure out what you will need to use in a bucket anyway.
Your manufacturer may call for different directions, but in general, you will use warm water to dissolve the chlorine. Make sure that you are using protective gear, and try not to breathe the mixture in.
Step 4: Pour the Chemicals Into the Water
Once you are done mixing your chlorine and have the amount that you will need to use, it is time to add the mix to the water. This is best done at night since most of your chlorines will be unstable and will not react well to sunlight. Check your chlorine product if you are not sure what type you have.
Poor it slowly around the pool’s perimeter. Try to stretch it so that you can complete a lap around the cool before all the contents have been emptied. The point is to give the chlorine an even distribution around your pool.
Step 5: Keep Pool Pump Running
Your pool’s pump is what circulates the water in your pool. This is primarily used for cleaning purposes, bringing the water through the filters to remove debris and other contaminants. You can use your pool’s pump to help diffuse the chlorine throughout your pool as well.
Your chlorine is going to need time to act. Depending on the brand or type of chlorine you bought, this can take between six to eight hours. If you are doing this at night, it is best to let your pool’s pump run overnight while you sleep so that your chlorine has a chance to do its work.
Step 6: Test the Pool Again
This part is very important – when you go back to your pool after having waited six to eight hours, check the pool’s chemical levels again. The normal free chlorine chemical levels in your pool should be between one to three ppm.
It can be hazardous to your health if you go swimming before the chlorine level drops to acceptable levels. Chlorine can cause lung damage and irritate your skin and eyes.
If your chlorine levels are still high, you can wait for the sun to take care of some of the excess levels of chlorine. If it is too high, you may need to use other chemicals to neutralize the chlorine.
Should You Chlorinate Your Pool Yourself?
If you are confident in your ability to follow manufacturer directions and you have no complicating factors in your pool’s chemistry, chlorinating a pool yourself will save you money. Treating your pool with chlorine is a beginner-level DIY project that takes less than an hour or two depending on the size of your pool.
In contrast, hiring a pool professional to chlorinate your water can cost you between $50 to $100 per hour. Assuming that you must chlorinate your pool once a week, you can wind up spending anywhere between $200 and $500 in one month. However, if you already have pool service and they include chlorinating your pool as part of the package, this may not be an issue.
Ultimately, whether you should chlorinate your pool yourself depends on your lifestyle and whether you have time to do it. Another consideration is when your pool’s chemistry has become overly complicated. Unless you have an understanding of what chemicals you must add to bring things back into balance, you may be better off referring the problem to a professional.
In either case, it is probably a good idea to gain an understanding of how to chlorinate your pool. This will help you make sure that your pool is maintained and safe for swimming.
How Much Does it Cost to Chlorinate a Pool?
The cost of chlorinating your pool depends on the type of chlorine your purchase, but chlorine tablets cost an average of $25 a month in use. If you have a small pool or a spa, you will only use a small amount of chlorine as compared to a large pool, and thus, your costs will be lower.
You will also need to buy test strips to check the pH and chlorine levels of the pool. Assuming you are checking your pool every few days, you will need around 12 strips a month. A set of 50 test strips costs around $7.
Shocking your pool uses the same steps as above, but increases the chlorine content higher than normal. You will want to shock your pool at least once a month while you are using it. The cost to do this is roughly $20 a month.
We mentioned above how much it costs for professional pool service. If you have a large pool that requires professional maintenance anyway, then letting a professional take care of it might make sense. However, for a small pool, paying professional rates makes less sense.
Chlorinating your pool yourself is a chore and will cost you a little bit of time. However, it can save you money in the long run, especially if you have a smaller pool.
Chlorinating a pool can seem complicated up front but is fairly straightforward once you know what type of chlorine you will use for your pool. If adding chlorine to your pool makes you uncomfortable, there are low-chlorine or non-chlorine options that you can consider as well. If you want to explore these options, speak to a pool care professional today.
Ruben has a diverse background in the home services industry, with experience running a construction company, a kitchen and bath showroom, and a moving and relocation company. This breadth of experience has provided him with a wealth of knowledge and expertise in various areas of home improvement in general and specifically in the heating and plumbing niche.