Most of my gardening is done indoors with hydroponics, but I’m also a big fan of container gardening. Especially self-watering container gardening!
This self-watering bucket container is very similar to a hydroponic wick system. Just like a hydroponic wick system, the soil & perlite in the “wicking cup” allow the soil to wick moisture from the water reservoir up into the main container. The only differences with this system are the lack of aeration and the presence of soil.
TIP: If you don’t have a tool to cut PVC pipe, most big box store have cutting stations in the lumber area. Take the small sections of PVC pipe to the cutting stations and cut them down to the size you need before leaving the store.
Build a Self Watering 5 Gallon Bucket
How to Build a Self Watering 5 Gallon Bucket
Total Time: 1 hour
Step 1: Identify the Top & Bottom Bucket
This may seem like a “no brainer”, but it’s easy to get mixed up and cut the wrong hole on the wrong bucket. To avoid this, identify the top and bottom bucket before getting started.
To make things even easier, label each bucket with a permanent marker for quick reference.
Step 2: Mark & Drill Overflow Hole in Bottom Bucket
Using a tape measure & permanent marker, make a mark that is 2 3/4” up from the bottom of the bucket.
Using the mark as a center-line, cut the overflow hole using a 1” hole saw.
Step 3: Install Overflow Pipe
Insert a 3/4″ inside diameter rubber grommet into the overflow hole.
Insert a 4-inch long section of 1/2″ PVC pipe into the rubber grommet.
The rubber grommet will hold the overflow pipe securely in place, and prevent water from leaking before it reaches the overflow pipe.
Step 4: Drill Holes in Wicking Cup
Using a 1/8” drill bit, drill holes in a 1-quart wicking cup.
Drill multiple holes on the sides of the cup.
Drill 4-6 holes along the top rim of the cup.
Drill 4 holes in the bottom of the cup.
The holes allow water to be wicked up into the top container and also allow the top container to drain into the lower bucket reservoir when oversaturated from rainfall.
Step 5: Mark Holes For Wick & Fill Port
The wicking cup will work best when centered on the bucket bottom.
Using a permanent marker, trace the profile of the wicking cup rim along the bottom side of the top bucket. The line you just traced will be too large for the cup. Remove the cup and trace a new line using the original as a reference. This new line should be approximately 1/8-1/4″ smaller than the original.
It’s better for the hole to be too small for the cup. You can easily expand the hole a little bit at a time until the cup fits perfectly.
TIP: To get a more accurate cut line for the wicking cup, use a second 1-quart cup and cut the bottom off of it. This will allow you to mark the cut line from inside the cup.
Using a tape measure & permanent marker, make a mark that is 2” in from the outer edge of the top bucket. This will be the center-line for cutting the fill port.
Step 6: Cut Holes For Wicking Cup & Fill Port
Use a jigsaw, Dremel, or razor knife to cut the hole for the wicking cup. Make sure to stay inside the cut line you drew earlier.
TIP: If you’re using a razor knife, make several scouring passes along the outline before attempting to cut deeply into the bucket.
Cut the hole for the fill port using a 1 1/4″ hole saw with a drill. This hole will be just small enough that it will friction fit the 1″ PVC pipe. Friction fitting the 1″ fill port will prevent soil from entering the bottom reservoir.
NOTE: Using a 1/8″ drill bit, drill several holes on the bottom of the bucket to keep the soil drained well.
Step 7: Test Fit Wicking Cup
Test fit the wicking cup to make sure it fits snuggly, but not so tight that the cup will eventually break during use. If the cup fits too tightly, carefully trim more material off the bucket.
A snug-fitting cup will make it easier to mark the mounting height for the top bucket. In the picture, you can see the waterline marking around the 12oz line on the cup. The cup is submerged in water up to this point, and the area above the line is an air gap between the water and the top bucket.
Step 8: Mark Top Bucket Height
Top & Bottom Bucket
With the wicking cup snugly fit into the top bucket, gently lower the top bucket into the bottom bucket until the cup touches the bottom of the bottom bucket.
Using a permanent marker, mark a line around the top bucket to indicate how far down the top bucket should be mounted. It’s not terribly hard to do this by yourself, but is easier if you have someone to hold the buckets in place while you mark them.
Step 9: Drill Mounting Holes
Top & Bottom Bucket
Using a 1/8″ drill bit, drill 4 mounting holes through the top & bottom buckets. One hole in the front, back, & each side is plenty.
Make sure to keep the top bucket on the mounting line you marked earlier.
This is another step that’s easier if you have a helper!
Step 10: Attach Top Bucket to Bottom Bucket
Top & Bottom Bucket
Using 1″ self-tapping screws, screw the top and bottom buckets together on the front and both sides.
TIP: Don’t install the back screw yet. The fill tube needs to be fitted first.
Step 11: Drill Drain Holes in Fill Tube
Using a 3/8″ drill bit, drill 4 holes in the bottom end of the fill tube. These holes are drilled in case the bottom of the fill tube gets blocked by sediment or dirt in the bottom reservoir.
The crusty brown on the pipe is the waterline from last growing season.
Step 12: Install Fill Tube
Having the front and side screw installed will make friction fitting the fill tube easier. The first time you install the tube it will be really tight, this is good as it will create a tight seal around the pipe.
With the drilled end of the pipe facing down, push the pipe through the hole into the bottom bucket until it hits the bottom. Raise the pipe back up approximately 1 inch off the bottom of the bottom bucket. This doesn’t need to be exact.
TIP: Before you install the fill tube, flip the bucket handle to the front. If you don’t do it now, you won’t be able to pick the bucket up by the handle because it won’t swing over the top of the fill tube.
Step 13: Attach Fill Tube to Bucket Wall
Hold the fill tube against the bucket wall. Using a 1/8″ drill bit, drill through the original mounting hole on the bucket into the PVC pipe.
Once the hole has been drilled, install the final 1″ self-tapping screw through the buckets and into the hole drilled in the PVC pipe.
WARNING: Please hold the pipe against the top of the bucket to keep your hands away from the drill bit.
Step 14: High Five, You Made it!
Congratulations! You should now have your very own self watering 5 gallon bucket!
Did you notice that I forgot to flip the handle forward as I recommended to do in step 12? ??
Estimated Cost: 10 USD
- (2) 5-Gallon Bucket
- (1) 1 Quart Cup or Similar
- (1) 4″ Section of 1/2″ PVC Pipe
- (1) 2′ Section of 1″ PVC Pipe
- (4) 1″ Self-Tapping Screws
- (1) 1″ Inner Diameter Rubber Grommet
- 1/8″ Drill Bit
- 3/8″ Drill Bit
- 1 1/4″ Hole Saw
- Jigsaw or Razor Knife
- Tape Measure
- Hand Saw (to cut PVC pipe)
🏆 Hard to Over Water
The overflow drain in the bottom bucket makes it incredibly hard to over water plants. This drain also works wonderfully during natural rainfall as the lower bucket will continually allow the container to drain.
Reduced Fungal Growth & Insect Activity
Bottom watering allows the top layer of soil to form a fairly hard crust that will make the container less appealing to both fungal growth and damp soil loving insects. Many insects that damage plants and root systems need damp soil to lay eggs on. Maintaining a hard outer crust at the top of the container discourages insects from taking up residence.
Reduced Soil Compaction
Over time, top watering plants can lead to soil compaction. Reduced oxygen levels, poor water dispersion, and the suffocation of beneficial bacteria are all effects of soil compaction. When soil is compacted, the pores of the soil become very small and are unable to provide room for both oxygen and water. Root death can occur as water enters the compacted soil and evacuates air molecules from the constricted soil pores.
This self-watering container relies on bottom watering and provides the root system and soil with oxygen from above and below the soil. The overflow drain in the bottom bucket is placed to allow for airflow above the waterline.
Healthy Root Systems
This year, both of my tomato plants grew roots all the way into the water reservoir in the bottom bucket. This resulted in beautiful healthy white roots like you would expect to see in a hydroponic system. Since the bottom of the bucket has both water and oxygen, the roots grew extremely well and produced tomatoes from July until Thanksgiving day. A heavy freeze on Thanksgiving day spelled the end for the otherwise still producing plants.
Easy to Move
Self-watering 5-gallon containers are easy to move compared to larger containers. You’re basically moving 5 gallons of soil, the plant, and around a gallon of water. The container also slides easily on a deck, porch, or patio.
Container gardening has one inherent limiting factor, the size of the container. I prefer using 5-gallon buckets because they are cheap and easy to move, but a larger container will allow you to grow larger plants.
Limited Plant Varieties
If you choose to use a 5-gallon bucket for your container, you will want to stick with container variety tomatoes. Larger tomatoes will suffer from insufficient space for root growth and will underperform. With that said, there are a lot of great container varieties of tomatoes to choose from.
Soil Mixture & Fertilizer
When growing tomatoes, I fill my self-watering 5-gallon buckets with a potting soil & perlite mix. A ratio of approximately 3 parts potting soil to 1 part perlite should help maintain a well-aerated soil composition that will promote healthy root development all season. Sifting large particles out of the potting soil will also help provide a more hospitable growing environment for your plants.
I use Happy Frog granular fertilizer when I first transplant a tomato plant into the container, and then once monthly afterward to maintain the nutrient levels required to produce those big tasty tomatoes. Rainfall will help flush depleted fertilizer salts out of the soil. If your plants experience heavy rain, it’s a good idea to add a small amount of fertilizer to the soil to replace flushed nutrients.
Filling the Self Watering 5 Gallon Bucket
How you fill the self watering bucket is simple, but important.
The wicking cup needs to be filled with potting soil. Sift or remove large chunks of wood and debris from the potting soil before filling the cup. Once you’ve filled the cup with potting soil and patted it down, place the cup back into the bucket.
With the wicking cup placed in the bucket, add perlite around the bottom of the top bucket. This layer of perlite will help the bucket drain properly, without dropping a lot of soil into the lower reservoir. The layer of perlite should be even with the top of the wicking cup, but not taller.
The remainder of the bucket should be filled with the potting soil and perlite mix. Don’t overfill the bucket. Leave the soil about 2-3 inches below the top of the bucket.
The soil mixture mentioned above works great to keep the soil light and airy throughout the growing season.
Priming the Bucket
Self watering wicking buckets need to be primed. Once a plant has been transplanted into the bucket, fill the lower reservoir with water & then soak the soil thoroughly.
As the soil begins to dry out, it will naturally wick moisture from the lower reservoir.
How Well do Self Watering 5 Gallon Buckets Work
Self-watering buckets work incredibly well, especially for new gardeners who are worried about overwatering or underwatering.
The lower reservoir holds enough water to keep thirsty plants like peppers and tomatoes happy for several days without additional watering.
Even in the summer heat, the constant supply of water keeps plants hydrated and healthy.
Since the soil is not directly watered, it’s basically impossible to overwater plants. Rainwater drains through the soil, down into the reservoir, and out the overflow drain.
What Do You Think?
I love these self watering 5 gallon buckets, and I hope you find them useful and easy to build. Let me know what you plan to grow in them, or even share what you’ve done to create your own customized gardening containers!
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