How Much Vitamin C to Dechlorinate Water

How Much Vitamin C to Dechlorinate Water?- Mathematically Explained

Chlorine in your water can be really harmful to your hydroponics. In fact, it could kill the plants over time. Therefore, you need to dechlorinate the water to ensure maximum safety for your plants.

Hence, to dechlorinate water, using Vitamin C is one of the easiest and safest ways.

So, the question naturally arises, “How Much Vitamin C to Dechlorinate Water?

The amount of required Vitamin C depends on the volume of water and the chloramine concentration. First, find the mass of chloramine present in the water. Then divide it by the molar mass of chloramine. Finally, find the value for Ascorbic acid per mol and multiply it by the molar mass of Vitamin c. This is the amount of Vitamin C you’ll need.

Sounds gibberish? Here we’ve explained everything step by step with examples for your ease. So, read along to dechlorinate some water!

2 Ways to Dechlorinate Water with Vitamin C

There are two different ways you can use Vitamin C to dechlorinate water. The first one is to use Ascorbic acid. And the second one is by using Sodium Ascorbate.

For your info, Sodium Ascorbate is another form of Ascorbic acid. However, there are some differences between these two Vitamin C components. Let’s understand the differences first. This way, you’ll be able to understand which one would be the perfect component for you.

Ascorbic Acid

Ascorbic acid is also known as unbuffered Ascorbic acid. Using Ascorbic acid will slightly decrease the pH of the water. We’ll see how the whole thing works as we go.

If the pH of your water is slightly higher than usual, it will be better to use Ascorbic acid. This is because it’ll dechlorinate the water as well as decrease the pH.

Sodium Ascorbate

The second type of Vitamin C you can use is Sodium Ascorbate. It is also known as buffered Ascorbic acid.

Sodium Ascorbate is recommended when you don’t want the pH of the water to change. We’ll learn about this too in the next segments.

So, without any further ado, let’s get started!

What Purpose are You Using for?

In almost everywhere, chlorine is added to water in order to eliminate harmful microbes. In some places, the amount of chlorine present in the water would not be an issue.

So, it’s necessary to balance the chlorine level of the water in order to protect the plants.

And as we’ve seen, we can use two forms of Vitamin C to dechlorinate aquarium water. The amount of Vitamin C to use depends on the volume of the water, and the current chlorine level.

Now, let’s see how to figure out the amount of Ascorbic acid needed to dechlorinate water.

How Much Vitamin C Do You Need if Using Ascorbic Acid?

First, let’s see how to dechlorinate water using Ascorbic acid. We don’t want to sound like your grumpy high school chemistry teacher. But it is important to understand the reaction between Ascorbic acid and chlorine.

C5H5O5CH2OH + HOCl → C5H3O5CH2OH + HCl + H2O

Ascorbic acid + Hypochlorous acid → Dehydroascorbic acid + Hydrochloric acid + Water

When chloramine is added to water, it reacts with the water and forms Hypochlorous acid. Hence, the chlorine we’ll be neutralizing is the Hypochlorous acid (HOCl).

Then if Ascorbic acid is added to water, the HOCl breaks down and forms Dehydroascorbic acid, Hydrochloric acid and water.

Previously we said that using Ascorbic acid slightly decreases the pH of the water. We already know that acids decrease the pH value of elements. Here, the newly produced Hydrochloric acid (HCl) is the reason the pH decreases.

Now, let’s calculate the amount of Ascorbic acid necessary to dechlorinate water.

Step 1: Find the Chloramine Mass

First of all, we need to find the mass of chloramine present in the water. In order to do that you can use this formula below-

Chloramine mass = Volume of water to treat (L) * Chloramine concentration [ppm (mg/L)]

Let’s say, you need to dechlorinate 1 gallon (3.78541 liters) of water. And the chloramine concentration in your area is 2 mg/L.

You can find the chloramine concentration from your local water quality report. You can search “[Your town name] water quality report” on Google.

Or you can simply use these test kits to measure the pH and chlorine in your water-

Now, to calculate the chloramine mass, multiply the volume of water with chloramine concentration.

For Our Example Case Scenario-

3.78541 * 2 = 7.57082 mg

This means, if the chloramine concentration in your area is 2 mg/L, the mass of chloramine in a gallon of water is 7.57082 mg.

This means we will be neutralizing 7.57082 mg of chloramine.

If you have 40 gallons of water, then put 40 * 3.78541 = 151.4164 to convert the water volume in liters first. 

Step 2: Convert the Mass Into Gram

For the second step, we need to convert the chloramine mass into grams. The formula to do this is-

Chloramine gram mass = Chloramine mass / 1000

For our example case scenario-

7.57082 / 1000 = 0.00757082 g

Now you might be asking, why do we need to convert it into grams.

In our next step, we need to calculate the mol value of chloramine. And this requires the gram unit of weight.

Step 3: Find the Mol Value of Chloramine

To find the mol value of chloramine, we need to divide the weight of chloramine by 51.476. Because 51.476 g/mol is the molar mass of chloramine.

The formula is,

Mol chloramine = Chloramine gram mass (g) / 51.476 (g/mol)

For Our Example Case Scenario-

0.00757082 / 21.476 = 0.000147075 mol

Step 4: Find the Value for Ascorbic Acid Per Mol

Now we have to find the value of Ascorbic acid per mol in order to calculate the mass of Ascorbic acid.

Mol Ascorbic acid = Mol chloramine * 1

For our example, the value is, 0.000147075 * 1 = 0.000147075 mol.

Step 5: Find the Amount of Ascorbic Acid Needed

Now for the fifth and final step, we’ll find the amount of Ascorbic acid to dechlorinate the water. To do that, we have to multiply the value of Ascorbic acid per mole with its molar mass.

The molar mass of Ascorbic acid is 176.12 g/mol. Therefore, the formula is,

Mass of Ascorbic acid needed (g) = Mol Ascorbic acid * 176.12 (g/mol)

For Our Example Case Scenario-

So, the required amount of Ascorbic acid for our example is,

0.000147075 * 176.12 = 0.025902806 g

So, we get that we’ll need 0.025902806 g of Ascorbic acid to dechlorinate 2 mg/L chloramine in 1-gallon water.

If you want the result in mg value, just multiply the gram value with 1000, and off you go!

To save you the hassle, you can get your hands on Ascorbic acid right here-

One interesting fact about the reaction is, it takes less than 1 second to dechlorinate water!

How Much Vitamin C Do You Need if Using Sodium Ascorbate?

Now comes the second method of dechlorinating water using Vitamin c. The Vitamin C we will need for this method is Sodium Ascorbate. The chemical formula of using Sodium Ascorbate with chloramine is-

C5H5O5CH2ONa + HOCL → C5H3O5CH2OH + NaCl + H2O

Sodium Ascorbate + Hypochlorous acid → Dehydroascorbic acid + Sodium chloride + Water

If we add Sodium Ascorbate with chlorine, it will form Dehydroascorbic acid, Sodium chloride and water.

In the previous method, we got Hydrochloric acid (HCl) as a byproduct. But in this case, we get Sodium Chloride (NaCl) which is a salt. Salt is a neutral component and therefore, this does not change the pH value of the water.

Now let’s find the amount of Sodium Ascorbate to dechlorinate water.

For your ease of understanding, we will be using the numbers from the previous example. Which is, 1 gallon of water and 2mg/L choramine concentration.

The first three steps of the calculation are just like the first three steps of the previous method. From that, we get the mol value of chloramine, which is 0.000147075 mol.

Next, we have to find the value of Sodium Ascorbate per mole.

To do that, we need to multiply the mol chloramine by 1.11. Because the concentration of Ascorbic acid is relatively less in Sodium Ascorbate.

So the value of Sodium Ascorbate per mol is, 0.000147075 * 1.11 = 0.000163253 mol

For the last step, we just have to multiply the value of Sodium Ascorbate by 176.12. Because, as we said earlier, 176.12 is the molar mass of Ascorbic acid.

Therefore, we get-

0.000163253 * 176.12 = 0.028752114 g

This means we will need 0.028752114 grams or 28.75211416 milligrams of Sodium Ascorbate.

You can get your Sodium Ascorbate from here-

Can You Use Vitamin C Tablets an Alternative?

We’re not done yet! There’s another simpler alternative to dechlorinate water with Vitamin C tablets.

So we’ve already said before that Ascorbic acid and Vitamin C tablets are the same things. Most of the time, the tablets are buffered Ascorbic acid; which is Sodium Ascorbate.

In this case, check whether your Vitamin C tablets are buffered or not. If they are buffered, follow the same procedure as using Sodium Ascorbate. If they’re unbuffered, follow the procedure of using Ascorbic acid.

Now, the tablets come in different concentrations e.g. 500mg, 1000mg, 1500mg, etc. In this case, the best way to use the tablet is to crush it into powder first. Then if your tablet is 500mg and you need 50mg, take 1/10th of the powder. If the tablet is 1000mg, use 1/20 of the powder.

The necessary amount of chlorine is crucial for plant growth. But the plants can get that amount from the soil by themselves.

Any extra amount of chlorine is rather harmful to the plants. Not only hydroponics but chlorine can also get in the way of growing algae. So, getting rid of this chlorine is really necessary.


Does boiling remove chlorine from water?

Yes, boiling water removes chlorine from water. If you boil water for at least 15 minutes, it will evaporate the chlorine from the water. And after cooling it down, you can use the water for your purpose.

Is too much Vitamin C harmful to aquariums?

The extent of using Vitamin C for dechlorination is not harmful to aquariums. But using too much Vitamin C will lower the oh value of the water and might harm the fishes and the plants.

Is Vitamin C necessary for fish?

Vitamin C is an important component for the health of fish. It helps the cells of the fish’s muscles, teeth and bones to keep together through collagen synthesis.


We hope you got your answer to how much Vitamin C to dechlorinate water by now. But always remember, using too much Vitamin C could also harm your plants.

If you have any other queries, please feel free to ask us in the comment box.

Till then, hasta la vista!

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