Chlorine v Chloramine: What's the difference?
This article is part of our complete collection of guides designed to help you choose the best water source, improve water quality, manage pH and nutrients, and keep your Tower Garden growing at its best.
← Return to the Tower Garden Water Guide
If you've been growing hydroponically or aeroponically for a while, you've probably heard this advice:
“Just let your city water sit out for 24–48 hours and the chlorine will evaporate.”
That advice can work when chlorine is the disinfectant in your water. But there's an important catch: many municipal water systems use chloramine instead.
And chloramine doesn't behave the same way.
In This Guide
Chlorine vs. Chloramine: What's the Difference?
Both chlorine and chloramine are used by water utilities to disinfect drinking water. The important difference for growers is how long they remain in the water.
🧪 Chlorine
- Used to disinfect municipal water.
- Doesn't remain as stable in water as chloramine.
- Can dissipate when water is left exposed to air.
- This is where the familiar advice to let tap water sit comes from.
💧 Chloramine
- Formed by combining chlorine with ammonia.
- More stable and longer-lasting than chlorine.
- Designed to remain effective as water travels through the distribution system.
- Simply leaving the water sitting out is not an effective way to remove it.
💧 The important part for growers: If your water supplier uses chloramine, filling a bucket and leaving it out overnight isn't the same solution that it can be for chlorine.
Why Do Water Utilities Use Chloramine?
Chloramine isn't used to make life difficult for gardeners. Its stability is actually one of the reasons some water utilities use it.
A municipal water system may need to keep water disinfected as it travels many miles from the treatment facility to homes and businesses. Because chloramine lasts longer in the distribution system than chlorine alone, it can help maintain that disinfection over greater distances.
So from the perspective of a water utility, that stability can be useful.
For a hydroponic grower, however, that same stability means you can't assume the disinfectant will disappear just because the water has been sitting for a day or two.
Why Does This Matter for Hydroponic & Aeroponic Growing?
Water is the foundation of any hydroponic or aeroponic system. Your plant roots depend on that water for both hydration and the nutrients you've added to it.
That makes knowing what's in your source water especially important.
When you're troubleshooting a Tower Garden or other hydroponic system, it's easy to focus immediately on nutrients, pH, lighting or the plants themselves. But your starting water should be part of that troubleshooting process too.
🌱 Start with the water. Before adjusting nutrients over and over because plants don't look right, find out what kind of water you're putting into the reservoir.
This doesn't mean every problem in a hydroponic garden is caused by chlorine or chloramine. Far from it. But knowing your water source removes one important unknown when you're trying to figure out why plants aren't performing as expected.
Does Letting Tap Water Sit for 24–48 Hours Work?
It depends on which disinfectant your water supplier uses.
| Water Disinfectant | Will Letting the Water Sit Help? |
|---|---|
| Chlorine | Yes. Free chlorine can dissipate when water is left exposed to air. |
| Chloramine | No. Simply allowing the water to sit is not an effective way to remove chloramine. |
This is why the old advice can be confusing. Two growers can follow exactly the same routine and get different results simply because their municipal water isn't treated the same way.
⚠️ Don't assume your water contains chlorine just because it's municipal tap water. Check with your water supplier to find out whether it uses chlorine, chloramine or another treatment method.
What Should You Do If Your Water Contains Chloramine?
If your water supplier uses chloramine, don't rely on letting the water sit before adding it to your Tower Garden.
Instead, use a water treatment or filtration method that is actually designed to reduce chloramine.
🚿 An Easy Option: Filter Your Water at the Hose
For growers filling their Tower Garden or hydroponic system from an outdoor hose, we carry the GrowRite Garden Hose Filter.
It's designed to reduce both chlorine and chloramine, so you can filter your source water as you fill the reservoir rather than filling containers and waiting for the water to sit.
- Designed for chlorine and chloramine reduction
- Connects directly to a garden hose
- Simple option for filling Tower Garden reservoirs
- Can also be used when filling larger hydroponic growing systems
Whatever method you choose, make sure it addresses the disinfectant that's actually present in your water. A filter that handles chlorine isn't automatically the right solution for chloramine.
How Do You Know What's in Your Tap Water?
You don't need to guess.
If you're on municipal water in the United States, look for your water supplier's Consumer Confidence Report (CCR), sometimes simply called an annual water quality report.
The report provides information about your drinking water and its treatment. Your water utility may also explain its disinfection method directly on its website.
If you still aren't sure, contact the water provider and ask whether your water is disinfected with free chlorine or chloramine.
💡 Keep in mind: Water treatment practices can change. If you checked years ago, it's worth checking again rather than assuming your utility still uses the same disinfectant.
The Takeaway
- Chlorine and chloramine are not the same thing.
- Allowing water to sit can help free chlorine dissipate.
- Letting water sit is not an effective method for removing chloramine.
- Find out which disinfectant your water supplier actually uses.
- If chloramine is present, choose a filtration or treatment method designed to address it.
- Consider source water whenever you're troubleshooting a hydroponic or aeroponic garden.
Good hydroponic growing starts with understanding your water. Once you know what you're starting with, it's much easier to make good decisions about filtration, nutrients and pH.
Continue Learning About Tower Garden Water
Water quality is only one part of keeping the reservoir healthy. Continue with these Living Towers guides:
💧 Water Guide
Start with our complete guide to water sources, water quality, reservoir care and troubleshooting.
Tower Garden Water Guide →🌿 Nutrients
Learn how much Mineral Blend to use and how nutrient strength changes for young plants and different conditions.
Tower Garden Nutrients Guide →☀️ Light
Learn how much light your plants need indoors and outdoors and how light affects healthy growth.
Tower Garden Light Guide →🌱 Seeds & Seedlings
Learn how to choose, start and care for seedlings before and after they go into your Tower.
Seeds & Seedlings Guide →🐛 Pests & Diseases
Identify common plant problems and learn what to check when your plants aren't looking right.
Pests & Diseases Guide →🥬 Crop Library
Find crop-specific growing information for vegetables, herbs, leafy greens and fruiting crops.
Explore the Crop Library →
