Pool Filter Replacement / Installation

How Much Chlorine Goes In A Pool?

‘How much chlorine goes in a pool?’ is perhaps the number one question pool owners tend to ask. Here’s our handy guide to chlorinating your pool, from the experts at Hilltop Plumbing.

Maintaining the quality of water in your pool can be a time-consuming task.

It takes a lot of effort to ensure that the pH balance remains steady, that the surface is clean of algae and other unwanted substances, and, of course, that your pool water has the right amount of chlorine in it.

But ‘how much chlorine goes in a pool?’ is perhaps the number one question pool owners tend to ask.

The answer depends on a variety of factors.

But before we get to those, let’s consider why your pool needs chlorine in the first place.

What chlorine is and why your pool needs it

People put chlorine in their pools in order to disinfect their pool water.

Routine chlorine treatments destroy micro-organisms that have the potential to cause a number of serious health issues, including Legionnaires Disease, ear infections, and athlete’s foot.

Chlorine is a naturally-occurring chemical element.

When it is used to treat pools, it comes in an array of different forms, from chlorine gas and sodium hypochlorite, which is liquid, to calcium hypochlorite, which is granular, to lithium and chlorinated isocyanurates.

When these elements come into contact with water, they release an acid – hypochlorous – that sanitizes the water’s chemical composition.

So that, in short, is why chlorine goes in pools.

How much chlorine should go in my pool?

The size of your pool will be the major determinant of how much chlorine you should use to cleanse it. So it’s really important that, before you add the chlorine in, you know precisely how many gallons of water your pool holds.

In order to calculate that number, you can use the following formula: measure and then multiply together a) the length, b) the width and c) average depth of your pool before multiplying it by 7.5 for a rectangular pool, 6.7 for an oval pool or 5.9 for a circular pool.

(We’d recommend using an actual calculator for this!)

As a general rule, you should maintain your pool’s chlorine level between 1 and 3 ppm as a way of balancing the water’s acidity.

So, if the chlorine level is already 1 ppm and you want to put it higher, add 0.00013 ounces per gallon to raise the chlorine level by 1 ppm.

Then just multiply the number of gallons in the pool in order to find the correct amount of chlorine in ounces.

Why does the chlorine level in my pool change so much?

That’s a good question.

The chlorine levels in your pool will change for a bunch of different reasons.

For instance, chlorine is lost when it reacts with bacteria and other organisms that eat it up.

But it also evaporates when it is hit by sunlight. Indeed, naked sunlight is so effective in reducing chlorine that one hot day can reduce the chlorine levels in your pool by 90 percent.

Temperature is another big factor.

Bacteria grow better in warm water so, when bacteria proliferate, your chlorine levels go down.

A general rule of thumb is that you need to add twice as much chlorine to the pool to maintain an adequate free chlorine level for every 6 degrees Celsius (10 degrees Fahrenheit) rise in temperature above 26 degrees Celsius (80 degrees Fahrenheit).

How to shock your pool with concentrated chlorine

You might want to shock your pool with chlorine in order to cleanse it of any nasty, chlorine-eating elements. You can read about how to do that here.

But you should be really careful when you are doing it because you don’t want to get chlorine directly on your skin. Tip: always make sure you wear protective eyewear, a chemical mask, and gloves before embarking on the chlorination process!


So, how much chlorine should go in your pool partly depends on the size of your pool, the temperature you keep it at, and its exposure to sunlight. 

As long as you keep the chlorine levels within the recommended limits and take good care of your pool generally, your pool will be fine!.

It would be a better option to call the professionals if you are new and have no idea about chlorine and its limits.

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