Photo by Jong Marshes

Okay so, if you’ve ever had a potted houseplant, most of us just add a bit of tap water and the occasional fertilizer to keep those things going, right? Simple.

So it makes sense that when you upgrade to a full-on hydroponic garden instead of just a collection of potted plants, you’d just keep on using plain old tap water, right? Except that’s not right.

Tap water works fine for plants potted in soil because the potting soil is designed to be the right environment for plant roots. Plants growing in your hydroponic garden don’t have the same root environment as potting soil, and that means you need to use a different kind of water.

Here are your options for what to use to fill your hydroponic reservoir instead of water directly from the tap.

Preparing tap water for hydroponic use

First thing’s first. You need to know how your local water is treated. Tap water can be treated with chlorine or chloramine. If you have chlorine in your water, you can let the water offgas in direct sunlight for 24 hours to remove the chlorine.

It’s important to note that UV rays are required for breaking down chlorine fully.

This doesn’t work, however, for chloramine. To remove chloramine from water, you’ll need to dissolve a Campden tablet in the water. It only takes one tablet for 20 gallons of water. The good news is that if your water has both, these tablets will remove both the chlorine and the chloramine.

Of course, you can use a Campden tablet even if you only have chlorine, but it’s not necessary unless you need a batch of reservoir water really fast.

Once you’ve gotten those additives out, you’re not quite in the clear. You need to go ahead and test the baseline pH and TDS of your tap water because it actually varies from place to place. At that point, add your nutrient additives to the water and keep testing. Fertilizers and other additives can also affect water pH levels.

Once your nutrient solution is otherwise ready to go, you can then add a pH adjuster to get the levels where you want them to be.

If you’re really serious about hydroponics, a different route to go is to invest in a water filtration system that removes chlorine and chloramine from your tap water. Then you can skip the step of letting the water sit in the sun or using a Campden tablet.

Buying distilled water

Now that you know exactly how to prepare your tap water to be safe for your hydroponic setup, let’s talk about the easier option. You can just buy water ready to use, that has a neutral pH and TDS count. And it’s not anything fancy. It’s just distilled water.

That being said, you’re going to need a whole lot more distilled water for a hydroponic reservoir (depending on the size of your setup) than if you’re buying a gallon jug for things like food preparation. You would be paying much more money for all that distilled water than an equivalent amount of prepared tap water.

So it’s really only feasible to buy distilled water for your reservoir if you’re working with a really tiny hydroponic setup (which is absolutely possible).

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