how much water for 3-5-10-20-65 gallon pot

How Much Water For 3/5/10/20/65 Gallon Pot

Growing cannabis plants can be challenging. And an underrated challenge is knowing the water demand of the plants.

So how much water for 3/5/10/20/65 gallon pot?

A 3 gallon pot needs 1 gallon of water, 5 gallon pot needs 1.5 gallons, 10 gallon pot needs 3 gallons, and so on. But temperature, humidity, and air flow can increase or decrease the water demand. Knowing when and how frequently to water is also very important. 

This is just the tip of the iceberg. There is so much more you need to know about watering plants. But worry not because this article has everything you need.

How Much Water Does Cannabis Plants Need?

The necessity of needing to water plants needs no mention. But the amount of water differs based on my things.

how much water per pot size

Now many of you may think just watering cannabis plants is enough. But that is far from it. The amount, time, and way you water are all very important factors. 

To have a healthy plant when to water and how much to water is crucial. You must not drown the hem plant or dry it out. 

Just watering the plants every now and then is dangerous. Over watering cannabis plants is just as harmful as letting the plants dry.

So wondering how much water per pot size

Cannabis plants need water amounting to 25–33% of the pot capacity. This quantity of water provides the plant’s roots with everything it needs. And this much water will not cause any pooling and probable fungal issues.

Now let’s see the exact amount of water needed for different sizes of pots.

For 3 Gallon Pots:

For a plant in a 3 gallon pot, you will need about 0.75-1 gallon of water. Plants in smaller pots tend to soak up more water. 

So how much water for a 3 gallon pot? Around 1 gallon of water should suffice.

For 5 Gallon Pots:

For a plant in a 5 gallon pot, you will need about 1.25-1.65 gallons of water. Again, plants in smaller pots soak more water. This is true for 5 gallon pots as well. 

So we recommend more than 1.5 gallons of water for a 5 gallon pot.

If you wanna know which strain goes best with this, it’s Skywalker auto.

For 10 Gallon Pots:

For a plant in a 10 gallon pot, you will need about 2.5-3.3 gallons of water. Plants soaking up too much water should not be a problem in this sized pot. 

So around 3 gallons of water is recommended for a 10 gallon pot.

For 20 Gallon Pots:

For a plant in a 20 gallon pot, you will need about 5-6.6 gallons of water. 

Now we are talking about big pots. The problem with big pots is getting the water to the right place in the soil, to the roots. 

We recommend using 6 gallons of water. So focus on watering near the stem. The outer boundaries can be dry. 

For 65 Gallon Pots:

For a plant in a 65 gallon pot you will need about 16.25-21.45 gallons of water. 65 gallon pots are quite big and watering them properly can be hard. 

In 65 gallon pots, the water needs to be focused near the stem. The outer boundaries can be dry. 

The answer to how much water for a 65 gallon pot is around 20 gallons.

Necessity of Water in 4 Different Stages of the Plants Life

A seedling and a flowering plant do not need the same amount of water. And the frequency at which they need water is not the same as well. 

Here is a cannabis plant water needs chart based on different stages of the plant’s life. 

Life StageWater Needed 
GerminationEvery 4-7 days
SeedlingEvery 3-7 days
VegetativeEvery 2-4 days
FloweringEvery 2-3 days

These numbers are of course changeable depending on other factors. And just to be sure if your plant needs water, you can test the soil.

2 Methods of Knowing When the Cannabis Plant Needs Water

To be sure whether your cannabis plant needs water, there are some things you can do. 

There are 2 simple methods you can try. Them being:

Method 1: Testing the Soil

This is the simplest thing you can do. Stick your finger down the soil. Shove in down 1-2 inches.

If the soil is wet, there is no need to water. If the soil is dry, you will need to water the plant. 

This test can be done in pots of all sizes. But for bigger pots you may want to stick your finger down in multiple spots.

Method 2: Lifting the Pot

Lifting up the pot and feeling its weight to determine whether it needs water is another method. 

But knowing based on weight requires experience.

More importantly, this method can only be done on smaller pots. 10 or 20 gallon pots or bigger pots cannot be just lifted and weighted. 

For this method to work, you must first know how much the pots weigh after being watered. Pick the pot up after watering it and note down or remember the weight. At this stage, the pot should have an ample amount of water.

Now lift up the pot and feel the weight to understand whether it needs water or not. Pots without water will weigh much less.

3 Factors That Affect the Amount of Water Needed 

Growing indoor plants has the perks of being able to control different factors. Temperature, humidity, and air circulation play an important role in a plant’s water demand. 

So let’s see how the three factors affect the watering needs of a cannabis plant.


Temperatures affect the growth of cannabis plants. And there’s a certain temperature for growing marijuana. Warmer temperatures are better for the growth of cannabis plants. So naturally, faster-growing plants require more water.

On the other hand, warmer temperatures make plants lose moisture at a faster rate. The soil also soaks more water. Warmer temperature also means higher humidity.

So you will have to give more water during warmer temperatures. 

Relative Humidity:

Humidity represents the amount of water in the air. Plants naturally release water through leaves in a process called transpiration. 

The rate of transpiration depends on humidity. As the relative humidity rises, the transpiration of cannabis plants decreases. And if the humidity falls, the transpiration of cannabis plants increases. 

So if the relative humidity is higher, cannabis plants lose less water. So you will need to feed them less water as well. So in all cases, you need to keep a check on the humidity. Our choice is the Smart Guesser Digital Hygrometer. You can find it on amazon!

On the other hand, lower humidity makes cannabis plants lose more water. So you will need to water the plant more frequently.

There are many ways to control humidity indoors. Even humidity in the curing jar is controllable.

Air Circulation:

Air circulation is also something you have to consider for watering plants. More air movement means lower relative humidity. And on the other hand, less air circulation means higher humidity. 

So if you have high air circulation, through fans or windows, you will need to water more frequently. And less air circulation means your plant needs less water.

Note that air circulation plays an important role in pollination too. So you might want to control air circulation to know about neutralizing pollen.


Is rainwater better for cannabis?

Yes, rainwater is better for cannabis. Collecting and storing rainwater may be a hassle, but pure and uncontaminated rainwater is the best for cannabis plants. Pure rainwater contains the right amount of nutrients needed for the healthy growth of the plant. 

How much water for a 30 gallon pot?

Around 9 gallons of water is needed for a plant in a 30 gallon pot. Cannabis plants need water amounting to 25–33% of the pot capacity. So a plant in a 30 gallon pot needs 7.5 to 10 gallons of water. The demand may vary depending on different aspects. 

Can I water my plants with distilled water?

Yes, you can water your plants with distilled water but we do not recommend it. Distilled water is purified water and lacks the nutrients needed for a plant’s healthy growth. So if you just use distilled water you will notice hampered growth in the plant. 


Now we know how much water for 3/5/10/20/65 gallon pot. The amount can differ depending on other factors. 

Follow our guide and you should not face any problems. Good luck!

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