Hydroponic Water Guide (Rain, Distilled, Tap, And Well Water)

A lot of newbie growers out there tend to overthink about the type of water that they have to use in their hydroponic systems. There are several options available like rainwater, distilled water, tap, and well water. It must have made them wonder, what is the best type of water to use for a hydroponic system?

So, what is the best type of water to use for a hydroponic system? There are no critical differences between the previously mentioned types of water. However, there are some modifications that need to be done for every water type to eliminate any possible negative effects on your plants.

Choosing the right type of water is one of the first steps that any newbie grower must pass by in order to start growing plants hydroponically. They usually tend to get overwhelmed by the several available options like tap water, distilled water, and even well water.

I can understand how frustrated they feel, we have all been there, but in reality, any type of water can be used for growing plants hydroponically. The real question here is not what is the best water type for my system, but what are you going to do to make this water ready to be used by your hydroponic plants.

In order to use water for any hydroponic system, you will have to check critical key factors like pH, ppm, and other water contaminants. These key factors differ from one water type to another and you will have to take some extra steps in order to regulate these factors to be suitable for your plants.

First, you will have to learn what is the acceptable pH and ppm of the water you are going to use.

Hydroponic Water ppm And pH

Let’s face the truth, water content is the same regardless of its original source; well water and rainwater are the same in terms of the chemical composition. However, what differentiates one type from another is the ppm and pH of the water used.

As I have mentioned before, you can use any type of water as long as the ppm and pH are near the acceptable levels of hydroponics.

The ppm Of Hydroponic Water

The acceptable ppm for any type of water to be used in hydroponics falls between the 200 and 300 ppm range.

Before checking the exact ppm of the type of water that you are going to use, lets first know what does the word ppm stands for; ppm stands for parts per million which acts as a reference for how much minerals does the water contain.

Yes, I know that you are most probably doubting yourself and thinking that plants do use minerals, so the higher the ppm the better which is completely wrong.

Higher concentrations of minerals, mostly calcium and magnesium, in nutrient solutions can lead to salt buildups which can further escalate and lead to a nutrient lockout.

On the other hand, low mineral concentrations can lead to an imbalance when adding more hydroponic nutrients, so the ppm range should fall between the 200-300 ppm range for your plants to be in the safe side.

The ppm levels vary from one type of water to another according to the source.

Here are the ppm levels of several types of water:

  • Tap water: 50-700 ppm
  • Distilled water: 0.5 ppm
  • Rainwater: 70-80 ppm
  • Well water: 300-5000 ppm

The pH Of Hydroponic Water

Hydroponics need water with an average pH level of 5.5 to 6.5.

The pH levels of several water types do affect the way your hydroponic plants grow as much as the ppm level do. Moreover, the pH levels do vary significantly according to the source that the water originates from.

Hydroponic plants need an an optimum pH level to thrive in. This pH level allows the plant roots to absorb nutrients efficiently from the nutrient solution.

Any fluctuations in the pH levels will lead to the plant’s inability to absorb nutrients normally. This will lead to poor growth rate that will further escalate into the death of your hydroponic plant.

The following are the pH levels of several water types:

  • Tap water: 6 – 8.5 pH
  • Distilled: 7 pH
  • Rainwater: 5.0 – 5.5 pH
  • Well water: 6.5 – 8.5 pH

Can I Use Tap Water For My Hydroponic System?

A lot of newbies fall in this trick during their first year of growing hydroponics and I am sure that we all have been there.

Can I use tap water for my hydroponic system? Yes, tap water can be used to grow hydroponic plants. However, levels of ppm and pH must be strictly monitored and adjusted in order to eliminate any side effects on the plants.

Most newbies get excited and they start to build or purchase their hydroponic system and then comes the most important part which is the water type to use in order to start and grow their hydroponic plants.

Usually, they use the first thing that comes in their head which is tap water. They start to grow their first batch using tap water alongside other hydroponic nutrients only to find out that after a few days, their plants are starting to die.

What Are The Main Issues With Tap Water?

There are several problems associated with using tap water for hydroponics, and they are basically related to three main things.

The three main things are:

  • Chlorine
  • Chloramine
  • ppm


Chlorine is one of the main chemicals that the government use during the treatment process of water. So why does the government add chlorine to the tap water in the first place? The main reason why chlorine is used is because of how efficient it is in killing bacteria and microorganisms.

Of course, adding chlorine by the government is one of the many steps taken to eliminate the spread of disease throughout tap water. But unfortunately, the nutrient reservoir contains many beneficial microorganisms that shouldn’t be eliminated because of their extremely important roles in keeping the plant thriving as much as possible.


Chloramine is another chemical that the governments use in order to disinfect tap water. It consists of chlorine and ammonia. Sometimes governments decide to use chloramine instead of chlorine because it tends to stay longer in water.

This makes chloramine a great chemical compound to be used as a disinfectant for tap water, but for us, hydroponic growers, it makes it further difficult.


As I have mentioned before, water ppm does play a huge role in whether the plants will thrive in this hydroponic solution or not. The ppm of your tap water depends on where you live. Some states will have treatment facilities that produce harder water with high ppm, while others will produce softer water with lower ppm.

The hardness of the water is based on the following:

  • Soft: 0 – 60 ppm
  • Moderately Hard: 61 – 120 ppm
  • Hard: 121 – 180 ppm
  • Very Hard: More than 180 ppm

You can know the hardness of the tap water present in your state by checking out the shower and other tap heads in your house. If there is a build-up of rust, then probably the tap water you are getting is hard or very hard.

As I have mentioned before, hydroponic plants do thrive in water with a range of 200 – 300 ppm. So, if you are getting tap water that exceeds the 300 ppm range, it might not be the best fit for your hydroponic plants.

You might think that after all of these problems, tap water might not be the best option, but we can’t ignore that tap water is one of the most available and easy options for any hydroponic grower to choose from. All that you have got to do is simply turn on the tap and refill your nutrient reservoir.

In order to use tap water, you have to first treat all of the previously mentioned problems to make sure that your hydroponic plants will be safe from any chemicals present in the water.

How To Deal With Chlorine In Hydroponics?

There are two main ways to deal with chlorine present in any tap water: either you boil the water or place it under the sun.

Boiling water to remove chlorine

To remove the chlorine, simply boil the required amount of water for 15 mins. The boiling process can be pretty costly, especially if it adds up at the end of the month. I do not advice on using this option because of it’s additional costs which I consider unnecessarily.

Using the sun to remove chlorine

The UV rays have magical effects on breaking the chlorine present in water. All you have got to do is leave the water reservoir open to direct sunlight for 24 hours and its done, there will be no chlorine in your water anymore.

To get the maximum amount of sunlight, you have to place the water reservoir either in your backyard or on the roof of your house.

I do advice on leaving the water for two days instead of 24 hours just to make sure that the water have received sufficient amount of UV rays to break the chlorine.

How To Deal With Chloramine In Hydroponics?

As I have mentioned before, chloramine is much harder to break than chlorine, and that’s why it tends to last longer in water.

To get chloramine out of your water you have to use an active carbon filter. There are varieties of options available out there and you can choose what best suits you.

Another fast and easy option is to use campden tablets. These are sulfur based products that are used to sterilize several liquids. Campden tablets have shown a great ability in breaking down chloramine present in water and they are way easier to be used when compared to the installation process of carbon filters.

Can I Use Rainwater For My Hydroponic System?

There is another group of people who want to take it to the next level and use rainwater for their hydroponic systems. I know how wonderful and environmentally friendly it could be to collect rainwater and, at the same time, grow plants hydroponically. However, we must know, can rainwater be used for hydroponic systems?

So, can I use rainwater for my hydroponic system? Yes, rainwater can be used to grow hydroponic plants. But, you must first check several key factors in order to make sure that this rainwater is safe to be used.

Most people would want to hit two birds with one stone when using rainwater for hydroponics. In some states where rainwater is abundant, it could be one of the best options available.

For example, Hawaii and Louisiana have rainfall rates that are considered the highest among all states. It would make sense to use rainwater as the main water source for your hydroponic system.

As I have mentioned before, you have to check some key factors before using the collected rainwater.

Rainwater ppm

Rainwater has a range of 70-80 ppm. The ppm of rainwater does increase according to several factors. The pollution index of your state plays an important role in the ppm range of the collected rainwater.

In states where there are a lot of factories across several industries, the pollution index tends to increase which leads to increasing its ppm. As I have mentioned before, hydroponics tend to favor the 200-300 ppm range. If the rainwater ppm reaches levels higher than these, it can lead to the buildup of salts.

Rainwater pH

Rainwater has a range of 5 – 5.5 pH. Pollution tends to contribute heavily to the rainwater acidity. In polluted areas, there are high concentrations of sulfur dioxide and nitrogen oxides in the air. These compounds tend to react with rainwater and produce acidic rains with a pH as low as 4.

If it happens that you are living in an area where there are higher chances of acidic rains, I do think that adding a pH up solution before using the water can be a good idea.

How To Collect Rainwater For Hydroponics?

Almost all houses in the united states have some type of gutter system on their roofs. This gutter system will collect rainwater in an extremely efficient way to be used for hydroponics.

The only thing you would need is a plastic barrel that will be the storage for the majority of the collected rainwater. The barrel should be able to hold an average of 55 gallons of water.

In some situations where your hydroponic system requires larger quantities of nutrient solution or it just happens that you are living in a state where there are less frequent rains, I advise you to have more than just one barrel to collect as much rainwater as possible.

You will also have to keep in mind a very important aspect which is the first flow of rainwater. Typically, the first few gallons of collected rainwater will flush your roof from sediments like dust, particles and birds poop. These sediments will be highly concentrated in the first few gallons.

You have options when it comes to solving the first flush problem. A a first flush diverter can be a great choice to isolate the first few gallons from the rest of the collected water in order not to contaminate the entire barrel.

Another option is to install a wire mesh cover at the opening of the gutter pipe to act as a filter for sand and debris.


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