Introduction: Metal Water Trough Planters
Want to make cool water trough planters? So did I! Here’s how I did it.
Why water troughs?
Lots of reasons.
We live in an old house, and old houses tend to have lead in the soil. The nice folks at UMass tested our soil and confirmed it does, in fact, have lead. So we can’t have a normal garden in the ground.
Last year, we tried straw bale gardening. It was great, but some plants (namely basil, carrots, cabbage, a few others) did terribly in the bales.
Mrs. MakerJosh grew up with horses, and always liked the look of metal water troughs. Good old Pinterest showed us lots of ways it could be done, but no specific instructions for how to do it.
This spring, we decided to take the leap. I was going to build six galvanized metal water trough planters. Our garden would be half water trough planters, half straw bales.
Before we dive in, take a look at these beauties. Really drink them in.
Step 1: About the Project
Is it hard?
You’ll break a sweat. It’s not hard, but you’re moving around a lot. You’ll need basic carpentry skills. It’s mostly drilling and screwing (#thatswhatshesaid), so you’ll need a great drill.
Will it hurt?
How long will it take?
If you’re an idiot like me, one planter will take five hours. That includes three trips to the local hardware store.
If you’re not an idiot or if you follow these instructions, each planter will take 30-45 minutes to build.
How much do they cost?
$172 per planter. Link to detailed cost breakdown at the end.
Step 2: Materials
1) Watering Troughs
They’re called all differen things. Is this regional? “Feed troughs,” “food troughs,” “water troughs,” “watering troughs,” “stock tanks,” etc.
We tried to find a used one on our local Craigslist site, but didn’t have any luck. That’s definitely going to be your cheapest option. So start there, and try all the different name combinations above.
After striking out on used, we started looking for new. The two best sources we found were:
For the troughs that we wanted, the prices were about the same between Amazon and TSC. Since we get free delivery from Amazon and we didn’t want to rent a trailer, Amazon was the clear winner!
We ended up getting these “galvanized stock tanks” in the 90-gallon size. Pick whichever size suits your fancy.
They took about a week to arrive. They shipped via freight instead of the typical Amazon Prime UPS/Fedex. That meant we had to be home to sign for them when they arrived.
Trust me, you’re going to want wheels on these things. More on this later, but each planter was easily at least 300 pounds. If you fill the whole thing with potting soil, expect it to be over 600 pounds. They are BEASTS. If you don’t put wheels on them before filling them with soil, you’re not going to be moving them.
There’s another good reason to have wheels -- drainage. If you over-water or if it rains, you won't drown your plants since the planter is a couple of inches off the ground.
I spent a lot of time researching wheels that could handle the load and that would hold up outside. I ended up going with these.
Here’s what I looked for in wheels:
- Ability to hold at least 800 pounds for a pack of four.
- A locking switch so the water trough planters wouldn’t roll around.
- I would have preferred stainless steel or galvanized wheels. These were tough to find. My hope is that they wouldn’t rust too badly since they’ll be under the watering trough.
3) Bolts (size DOES matter)
I’ll be honest -- I picked the wrong bolts. And that messed me up, bigly. Trial and error with bolts is the main reason the first planter took five hours.
Here’s where you get to learn from my mistakes.
First, I got bolts that we were too skinny. They bent, stripped, and generally made life miserable. Don’t go with anything smaller than ¼”. I ended up with ¼”-20.
(LPT: want to know what numbers like ¼”-20 means? Here’s a good article.)
Next, I got bolts that were too long. I guessed that i needed 2” bolts, and had a grand ol’ time attaching that first wheel. It was a delightful surprise when I learned that the bolts were so long that the wheels wouldn’t turn.
So I pulled out my handy folding jab saw and cut the bolts off, and started over.
Last, I got the wrong metal. I know better. But I was in a rush. Zinc rusts. Stainless steel doesn’t. You need stainless steel.
So here’s what you want to use:
- ¼”-20 x 1-½” Stainless Steel Hex Head Bolts. Any longer than 1-½”, they’ll hit the wheels. Anything shorter, they won’t make it out the other side. You’ll need 16 per planter.
- ¼”-20 Stainless Nylon Insert Lock Nuts. Lock nuts are nice because they won’t come loose after they’re attached. Again, 16 per planter.
- ¼” Flat Washers. You’ll need 32 per planter -- one for the top of the bolt and one for the nut
4) Other stuff
Pressure Treated Wood
The bottom of the water trough planters are way too flimsy to support 800 pounds.
I was lucky because I had some wood leftover from a fencing project. I found that the wood commonly used on decks (5/4” by 6”) was perfect. You’ll need 36” (three feet) for each planter.
You’ll also need a roll of this stuff to make sure your potting mix doesn’t just wash away.
The Right Tools
There is no way I could have done this project without these tools:
- An excellent drill/driver. I recently upgraded to this puppy and it’s the best drill I’ve ever owned.
- Some sharp drill bits. You’ll be using the ¼” bit a lot. I also picked up this little kit, and am very happy with the quality.
- Oh my god you need this. I didn’t have the right size when I started the project. I picked one up on one of my trips to the hardware store, and it made things go so much more smoothly. These little adapters let me use a socket wrench on my drill.
- Good safety glasses and gloves. Definitely some sharp metal and wood flying around.
- A good tape measure. I have a few of these kicking around, love the ability for the tape to stand out unsupported.
- Tape to act as a second pair of hands. This is another trick I learned along the way. This Gorilla Tape was great because the troughs were a bit damp. This kind of tape actually thrives in slightly damp situations.
- A good socket set. For this project, it helps to have sockets that are a bit long, like this one.
Let's get to building!
Step 3: Step 1: Gather Your Things
If you ordered more than one watering trough, they will come nested.
We thought it was odd that the troughs are slightly different sizes. Once they're unpacked, though, we didn't notice it at all.
Step 4: Step 2: Cut and Place Your Wood
Cut two 18” lengths of pressure treated wood.
Place your wood and wheels in their approximate spots. You want the wood as far as possible to the outside edge, with the corners lining up with the edge of the planter. Do this for two reasons:
- to maximize stability and
- so that you can reach the wheel locks with your foot.
Step 5: Step 3: Place Your Wheels, Drill Your Holes
Measure 1 inch from each end of the boards to find where you'll mount your wheels.
Center the wheel on the board at the 1” mark, then use a Sharpie or pencil to mark your holes.
Get to drilling!
Re-position your board so that the corners line up with the edges of the watering trough. Put a lot of weight on the board to hold it in place, then grab your ¼” drill bit and start drilling holes.
(LPT: go slow! You’re drilling through an inch of wood and then metal. If you’re putting the right amount of pressure on your drill, it should take 10-15 seconds for each hole).
Once you’re done with a hole, drop one of your bolts into it. That will keep it in place as you drill the other holes.
Keep drilling holes and dropping in bolts until you finish that side (eight holes in all).
Step 6: Step 4: Flip the Trough, Insert Bolts
Flip the trough over.
Take the boards off, leaving the bolts in them, and place them to the sides of the planter. Be careful to keep them oriented in the same direction as they were when on the planter, so that your holes will line up.
Stack up a couple of your boards to raise one end of the trough off the floor. You’re going to need some room underneath for the bolts.
From the inside, put two bolts in each side (don’t try to do all four at once -- they’re actually really hard to line up).
Put a washer under each bolt head. Then cover them with a strip of tape to hold them in place.
Step 7: Step 5: Attach Your Wheels
Carefully flip your watering trough back over. You’ll be greeted with four friendly waving arms.
Line up your board over the bolts, and then set two of the wheels on top.
Here’s where the socket adapter tool really earns its keep.
Put washers and nuts on each bolt end and hand tighten. Then grab your drill and socket combo, and tighten those puppies down.
You want to be careful to tighten these just enough. Too much, and you’ll pull through the thin metal and the bolts will block the wheels from turning. Too little, and you’ll have wobbly water trough planters.
Using my trusty carpenter’s folding rule, I found that having the bolt end stick out about 3/16” from the nut was perfect.
Step 8: Step 6: Finish Attaching These Wheels
Flip your trough over again.
When you do, it’s likely that you’ll see that the wood has shifted a bit.
No worries! Just grab your drill and ¼” drill bit and re-drill the wood hole.
Then repeat the process, adding the other four bolts to the holes (with a washer on each one!), and taping them down.
Flip your trough over again. Put washers and nuts on the remaining bolt ends, and tighten them down. You’re now the proud owner of a half-made water trough planter!
If you look inside your planter, the bolt heads should be nice and snug up against the metal. If they’re not, you may need to loosen and tighten the nuts a couple of times to draw them in.
Step 9: Step 7: Rinse and Repeat
You now need to go through the same process to attach the wheels on the other side. As a reminder:
- Rough layout of wood and wheels
- Measure 1” from the end of the board, place your wheel, and mark your holes
- Hold tight, drill slowly, dropping bolts in as you go
- Remove the boards and bolts, flip the trough over
- Pop in four bolts and washers, tape them down
- Flip the trough over, and attach two wheels with nuts and washers
- Flip the trough back over, redrill your holes, then pop in four more bolts with washers
- Flip the trough back over and put on the final nuts and washers
When you're done, your planter will have four wheels.
Almost ready to go outside...
Step 10: Step 8: Drainage
First, drill 10 holes in the bottom of the planter with your ¼” bit. Just randomly space them out.
Finally, unscrew the water plug that ships with the water trough. That’s a perfect use for channel lock pliers, a plumbing workhorse in my toolbox: Now we’re ready to head outside!
Step 11: A Word About Weight and Drainage
As mentioned above, these suckers are HEAVY. I weighed one of the bags of potting mix -- it was 60 pounds.
It would take 6-8 bags to fill a water trough planter all the way up. That’s 360 – 480 pounds, not to mention the weight of the trough itself.
This would also be a huge waste of money, as vegetable roots don’t go down two feet.
Gardener’s Supply has a great summary of how much soil you need for each type of plant.
I was in the middle of a dump run when struck with inspiration. I saw multiple people wrestling with packing styrofoam. Not those annoying peanuts, but big stable chunks of styrofoam that can pad a TV.
10 minutes later, I was the proud owner of lots of free styrofoam. I was also the subject of five people looking at me like I was crazy when I told them that I’d take their styrofoam.
Step 12: Step 9: Final Assembly
Break up the styrofoam and place it in the bottom third of the planter, careful not to cover the drainage holes.
Make sure you have about 18” left for soil.
Then cover the styrofoam with landscape fabric. This will keep the soil from washing away.
It’s time to fill it up.
I forked in a few forks of partially-composted straw (from last year’s straw bale garden), then I filled the remaining space up with potting soil, leaving an inch or two at the top. It took 3-½ 50 qt. bags of potting mix to fill up top of each water trough planter.
You're all ready for planting!
Step 13: Final Thoughts and Recommendations
You can read a more complete write-up of this project at http://www.makerjosh.com/water-trough-planters/. We also have a detailed cost breakdown at the end, and some tips on saving money when you build it.
We also write a bit about the research that we did about the safety of galvanized metal for growing food, the use of styrofoam, and more.
Hope you liked this project!
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