How Long Does it Take for Free Chlorine to Evaporate From Tap Water Entirely ?

Surely many aquarists have heard that chlorine will leave facet water after some time.

But exactly how long does it take for tap water to be safe for fish?

Can the clearance be full without the use of chemicals?

What about his cousin – chloramine. There are numerous ways on how to remove chloramine from tap water as well, but is evaporation one of them? Is this an efficient way for dechlorination?

Chlorine is the go-to choice for water facilities because it is cheap and very hostile to bacteria.

It is also rather harmless to humans.

With our friends from EPA regulating things all over the place, we can feel at least a little safe, right?

Maybe.

But what about our fish pets?

Chlorine in tap water is quite toxic to them (some of us have learned that the hard way).

Dechlorinating tap water has become a healthy habit for every fishkeeper out there.

There are times, however, when we can’t really get our hands on them sweet water conditioners.

And we find ourselves wondering…

So how long does it take for chlorine to fully volatilize from tap water?

Depending on its levels of content, the evaporation time for chlorine from tap water can be estimated:

2 ppm of Chlorine will take up to 4 and a half days or around 110 hours to evaporate from 10 gallons of standing water. Ultraviolet light, circulation, and aeration will speed up the process dramatically. Boiling the tap water is the fastest way to remove Chlorine, and it will take between 6 and 8 minutes for 10 gallons.

Chloramine, however, doesn’t evaporate as quickly.

In fact, it is pretty stable.

It’s why companies use chloramine in the first place.

It does not gas-off as easily and it is more long-lasting.

Does boiling the water efficiently withdraw the Chlorine?

Boiling water does remove and will clear tap water from chlorine as heat reduces the ability of water to hold dissolved gas.

Here’s how fast will chlorine and chloramine degass when being boiled away:

The evaporation estimate of 1ppm of Chlorine when boiling 10 gallons of water is just above 3.5 minutes. However, it will take around 60 minutes (1 hour) of boiling to let out all of the Chloramine for the same amount of water.

A very important note:
Tap water chemical contents vary across states and countries.

There are places where water is either undrinkable or highly chlorinated.

The best way to gain insights on your particular tap water is to test it.

Chlorine VS Chloramine in our tap water?

Why you should care to know the difference:

Free chlorine is being kept in drinking water via pipe pressuring.

As soon as it leaves the sink there is no pressure to hold it inside anymore, and it starts to gas-off.

Chloramine, on the other hand, represents the chemical bond between chlorine and ammonia.

Nowadays there’s a good chance that your local authority uses chloramine for water disinfection.

This is the reason behind elevated ammonia levels after dechlorinating with a commercially available water conditioner.

The dechlorinator breaks the bond of chloramine and neutralizes the released chlorine, but the ammonia is still present.

I’ve said this many times, but I guess it’s better to be safe than sorry – always read the label of the products you use in the aquarium.

There are all-in-one solutions commercially available out there, you just need to find them.

Prime, for example, converts chloramine into chloride but takes care of the leftover ammonia as well.

Evaporation times – overview chart

Where I live, the total chloramine content is between 2.7 to 2.9 parts per million.

Being a fan of the scientific approach, I did a couple of tryouts and wrote down my results.

Some additional research showed that Chloramine has around 3.5 times longer time estimate for evaporation than chlorine, depending on temperature and pH levels.

This would mean that if it only takes 1 day for chlorine to evaporate it will take chloramine about 3.

Throwing in additional treatment techniques would change that ratio.

My water was usually around 7.5 – 7.6 pH during the tests.

I did take some measures. Comparing them I acquired some pretty interesting data.

I took the liberty of conjuring a table with estimated chlorine and chloramine evaporation-time periods:

Water treatment Quantity in Gallons / Liters 1 ppm of free Chlorine 1 ppm of Chloramine
Undisturbed 10 gal / 37.85 liters up to 55.3 hrs up to 173.4 hrs
Circulated 10 gal / 37.85 liters up to 9.6 hrs up to 70 hrs
Circulated, Aerated 10 gal / 37.85 liters up to 9.2 hrs up to 67.6 hrs
Boiling 10 gal / 37.85 liters up to 3.7 minutes up to 64.8 minutes
I deliberately calculated the values based on 1 ppm of Chlorine or Chloramine.

This way you can test your tap water and multiply the result with the values above.

For example, if your tap water tests for 3 ppm of Chlorine, multiply the middle column by 3.

It would be wise to call your authorities and ask which one they’re using for disinfection.

I did the tests in my garage to ignore the UV light factor (which, by the way, can be a gamechanger, but more on that below).

Other ways to get rid of the chlorine in tap water:

To naturally dechlorinate tap water try these methods:

1. Campden tablets – I will only mention this because I know it works.

My friend, who’s an avid home beer brewer shared this with me once (Thanks, Em!).

He uses Campden tablets (Sodium or Potassium Metabisulfite) to sterilize the water for brewing.

He swears by it being really effective in removing chlorine AND chloramine.

What did I do? I did my research.

Turns out people did use it to dechlorinate their fish tank water.

So I borrowed some from Em and gave it a go.

It absolutely works, by the way. No ill effect on my fish.

Plus it’s much cheaper than commercial conditioners.

The only catch is that you can purchase the stuff from specialized brewing shops, as far as I’m aware.

I moved away from where Em lived, so I lost my “dealer”.

One of those days, I may look into acquiring some K-meta again…

Anyway, after Em was kind enough to share his dechlorinating adventures with me I became interested in the subject.

Again, I performed heavy research.

Evidently, there’s another way of dechlorinating water.

2. Sodium thiosulfate – it’s the name and destroying all the bad chlorine is the game.

My findings did confirm that commercial facilities use this thing to dechlorinate the water.

However, I never experimented with this one, as people do report high ammonia levels after the treatment.

This leaves the whole “make the water safe for fish” concept behind.

Also, it seems to work with chlorine only, and not chloramine.

I would be happy to hear from you on this one.

Let me know your experience and I will upgrade this article with your report.

3. Moving water – Another useful tip Em gave me about dechlorination is that the more surface area the water has the faster the chlorine will evaporate.

Apparently, chlorine evaporates faster when in contact with air.

Thus recirculating the water will also speed up dechlorination.

Em told me a common old practice where you just move water from one container to another a couple of times.

This gives the water plenty of movement and contact with the air so the chlorine evaporates faster.

If you are okay with looking like a madman you can try it.

I know I wasn’t, so I came up with a workaround. Following this logic, I’ve found that using airstones will speed up dechlorination by almost a half.

One more thing you can do to speed up the process is reaching out to the… sun.

4. Ultraviolet light – Ultraviolet light gives chlorine AND chloramine enough energy to do some mysterious physics and makes them leave the water significantly faster.

When I was younger I used to work as a lifeguard during the summer months.

My duty would include maintaining the proper pH and Cl levels of the pool, to keep it safe and bacteria-free for our residents.

Some pools kept their chlorine levels steady throughout the sunny days and some couldn’t.

Baffled, I spoke to my supervisor, only to find out that the ones that had stable chlorine values were treated with UV protection in the form of cyanuric acid.

It was why they weren’t losing chlorine in the sun.

I also have two fellow aquarists (one keeps a reef tank and the other – a pond), reporting that by leaving a bucket (read 5 gallons) of water sit in the sun for a day would neutralize most Chloramine traces.

Don’t judge them, by the way – every fishkeeper has a moment when they don’t have access to an RO/DI device or a dechlorinator.

Some water facilities do use a method called low-pressure UV dechloramination, so there is merit to their anecdotes.

5. Activated carbon – Lastly, activated carbon filters will definitely get rid of the nasties.

There are such filters in most pitchers and also RO systems.

However, the carbon filters in pitchers will wear out way faster when dealing with chlorine or chloramine.

If you fancy the purifying tank idea, you can set up a filter media like this, to fasten the removal.

RO/DI/Distilled water is your best option.

These purifying methods will get rid not only of chlorines but also everything else that might harm your fish.

If you plan on maintaining a reef tank, proper water purification is a must, as marine life is VERY sensitive to the chemicals in tap water.

Distillation can be costly, but if money is not a factor for you (which I doubt if you’re reading this) then go for it.

Reverse osmosis systems come at the price of between $80 and $250, but it’s a very cost-effective investment.

They will save you many headaches, not only for dechlorination but also algae-favoring phosphate levels and whatnot.

It is really the purchase you should be after when you’re done gearing up your aquarium.

Don’t forget to remineralize after the purification (the link leads to a thorough explanation I wrote on purified water and fish tanks).

Set up your own DIY dechlorinator at home

Following these thoughts, here’s how to remove chlorine from tap water without chemicals at home:

You can set up a “purifying” glass container that sits under the sun with a filter, or perhaps, a wave maker, and an air pump.

This setup may take a day or two of running, but it will eventually get you rid of all the chlorine.

To me, this sounds super expensive just for the sole purpose of dechlorinating, even though the cheapest gear will do the work.

Still, I am obligated to mention it, as I know people that are doing it.

Technically it still counts as evaporation and you’re doing it without any chemicals.

Final Takeaway

Chlorine and chloramine can be removed from the water by off-gassing, but it will take some time.

However, there are many ways to hasten the process and still get the desired results.

You can share how it went for you, and we can have a nice discussion in the comments.

95.94% of the readers found this article helpful.

Tap a star to leave your vote:

1 Star2 Stars3 Stars4 Stars5 Stars (64 votes, average: 4.80 out of 5)

Loading...

I think you'll also like

15
Leave a Reply

avatar
7 Comment threads
8 Thread replies
1 Followers
 
Most reacted comment
Hottest comment thread
8 Comment authors
MomchilJamesaquadminRebeccaJack Recent comment authors

This site uses Akismet to reduce spam. Learn how your comment data is processed.

  Subscribe  
Notify of
Cici
Guest
Cici

Thanks for your research. You pretty much answered all my questions plus the ones I didn’t know I needed to know. You know? 🙂

Irina
Guest
Irina

Thank you very much for the article! I came across your blog while researching ways to remove chloramine from drinking water and for now boiling would be most suitable of all the methods. I use only about a gallon a day for drinking and cooking, and in that case would it take less boiling time than an hour to get chloramine out or does it not depend on the volume, and it would take the same amount of time to remove it from a gallon of water as it takes for10 gallons?

Reader
Guest
Reader

When it comes to the evaporation of water we know that @ STP the boiling point is 100 C. So when we leave water outside under the sun we see that it evaporates at a lower temperature. This has to do with the boltzman distribution of particles or your typical grade point average where those few high energy particles will escape as a gas while the rest will remain as a liquid. Through time (kinetics) the rest of the particles will evaporate.

Kim
Guest
Kim

I thought your article was really informative. You have really done your research! I’m going to try a couple of ways you suggested to lower the nitrite level in my tank.

Jack
Guest
Jack

Thanks for the info.
My water here in Oregon according to the water master has approximately.02-.04ppm of free chlorine in the water.
I guess I’m lucky that I live somewhere that has a cleaner supply.

Rebecca
Guest
Rebecca

If I drop an air stone into 18 L of tap water, and pump air bubbles through the water, how much faster will the chlorine evaporate?

James
Guest
James

How do I get hold of those pills Em “gave you?”
Thanks
James