Tips & Tricks for Designing a DIY Wash/Pack Tunnel

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Having an efficient wash/pack station on your farm is one of the most critical pieces of infrastructure to have in place when you first design your farm. When the first harvest starts, you don’t want to be scrambling around piecing something together last minute. You need to be able to wash, package and cool your product. Otherwise, all your hard work to finally reach the point of the harvest will be in vain. 

Design Considerations

Access to water and electricity, and close proximity to your growing space are the first things to consider when planning the construction of your wash/pack station. Next up would be what kind of structure to use. I’ve seen farmers convert half of their garage, a section of their barn, or an open-air lean-to off the side of a barn, a storage shed, or even a repurposed shipping container. Some choose to designate a portion of space inside one of their high tunnels.

At my family farm in California, I decided to use half of a 50’ caterpillar tunnel I had purchased from Farmer’s Friend LLC. We were in Petaluma, about 30-45 minutes north of San Francisco, and only 15 minutes from the coast. It was a temperate climate there, never getting too hot in the summer, or extremely cold in the winter. I was also leasing the land and wanted to build something fairly easy to take down since I knew moving would likely be in our future at some point. A 14’ x 25’ caterpillar tunnel was just the right size, and a lot more economical than the other options!

As I had previously lost a caterpillar tunnel in a windstorm earlier that year, I wanted to make sure it was extremely sturdy and protected from the wind. I situated it near the house (which was adjacent to the farm plot) and partially under a tree line for shade. The trees were also a buffer from the wind. 

I pounded in 4’ deep corner pipes for each corner of the tunnel, which the end hoops were then bolted to after being inserted. I then installed 2×6 toe boards at ground level that ran the length of the tunnel on either side. The plastic was securely fastened to the toe boards with wiggle wire and channel, as well as the end hoops. We also installed wind bracing on both of the end hoops and overhead cross bars above each hoop for added strength. This thing wasn’t going anywhere!

As you can see I used wood chips for flooring (which I sourced for free from a local arborist). For drainage, I ran a 2” PVC drain line to a drain pit located about 20 feet from the tunnel. Water was simply run from a hose off of the house, and a heavy-duty extension cord ran from the house to the tunnel for electricity. Nothing fancy, but it worked like a charm!

Even though the adjacent tree line partially shaded the tunnel, we ended up pulling 50% shade cloth over the tunnel to cool it down during the summer. The combination of the cross ventilation from the open end-walls, and the shade cloth pulled over the top kept it quite comfortable to work in.

Pex Plumbing

I decided to go with PEX tubing rather than the standard PVC and glue route. Working with PEX appeals to me for a lot of reasons:

  • Stretches if water were to freeze in the lines 
  • No toxic glue fumes 
  • No waiting for glue to dry
  • Super easy to cut
  • Can be moved and swiveled at joints and valves
  • No leaking

I liken working with PEX plumbing to legos: endless options and enjoyable to work with. I ran a line of PEX tubing along the inside of the toe board behind my sinks and tubs, with T valves to send water to the pressure pump, the fill valve for the greens bubbler, the sprayer hose, and the hand wash sink. 

The basic tools and supplies for working with PEX include:

Once you have the tools and a general understanding of how to use them, it’s seriously a fun task! Not only can you easily plumb all of your own wash/pack infrastructure, but you can also create your own irrigation manifolds (which won’t break like all of the over-the-counter ones).

A nice aspect of using the brass ball valves is that when they are in the open position, the opening is equal to the inside pipe diameter. This means your water isn’t getting squeezed, as it would with over-the-counter manifolds, ensuring you maintain the maximum flow rate. 

Note: I prefer the cinch ring clamps over the pressure ring clamps, as they allow you to pry them off without needing to cut and replace the tubing.

Pictured below is an inline pressure pump I plumbed into my wash/pack tunnel water supply. I only used this when I needed higher pressure to adequately clean off my root crops on the root wash table. The pressure from the house wasn’t adequate for this task. The pump, while a little noisy, solved this problem.

Hand Wash Sink

My handwash sink was just a salvaged standard porcelain sink that I built a stand for out of pressure-treated lumber. Again, nothing fancy, but it served the purpose well. With my workflow moving from right to left, I positioned it at the front of the line. Washing hands would be the first step of the process for anyone washing and packing the harvest.

Root Wash Table

For my root wash table, I decided to go with 24” x 40” laundry wash tub. For the top, I used a 24” x 48” segment of plastic greenhouse bench top from Berry Hill Irrigation. I trimmed off 8” so it would be a custom fit on top of the sink. The smooth surface was gentle on root crops like carrots, beets, and turnips. When I first built it I was using an expanded metal surface, but quickly learned that it could damage my crops if I wasn’t really careful, and it also scuffed up the bottom of my harvest totes. The smooth plastic was a much better solution.

The beauty of the root wash table was that I could also use it to sanitize trays and totes. I would leave the top on while washing or rinsing by totes, and then I would remove it for washing my trays, which would go inside the sink. 

Greens Bubbler

Next in line was the greens bubbler. Like many other market farmers, I went with the 100-gallon black Rubbermaid stock tank. I used 1.5” PVC for the blower piping in the base of the tank, configuring a rectangle with PVC elbows, and a cross-section in the middle with a T from which the stem piping came up–about 40”. I drilled ⅛” air holes about every two inches apart in the PVC rectangle at the bottom. To hold the piping on the bottom of the tank during use, I used two vinyl coated dumbbells. This prevents it from floating when air is pumping through it. All PVC was just pressure fit together, not glued. This allows for disassembly for periodic cleaning.

I also plumbed in a Hudson float valve which I HIGHLY recommend. It’s so nice to turn the water on and go do another task without worrying about forgetting to shut the water off and your tank overflowing!

On top of the main stem is where the hot tub blower was installed by being pressure fit into a rubber coupling. Note: tie the blower off to be suspended from above–just in case it were to pop off due to the air pressure. It’s also a nice feature for when you remove the piping for cleaning or use your tank for soaking roots, washing trays, etc. See the below illustration:

The stock tank sat on two concrete cinder blocks, situated on either end underneath the tank, creating space for the drain line in the bottom center. I cut a hole with a skill saw in the bottom center of the tank and installed a simple two-inch drain.

Greens Dryer

While I contemplated converting a washing machine into a salad spinner, I found such a great deal on a lightly used commercial greens dryer, that I decided to go that route instead. It was an Electrolux Greens Dryer, the VP2 “Greens Machine Vegetable Dryer w/Basket,” which sells new for $2,855. I found mine for $1500 on eBay! While I still could have saved money doing the DIY washing machine conversion, I had heard another farmer claim that the Electrolux was so efficient with the spin cycle being at just the right speed, that it eliminated the need for the additional step of spreading your greens out on a drying screen with box fans. 

Having regularly used a drying screen at the previous farm I had managed, I knew what a time savings this could be. I figured that between the time and materials to build a drying screen setup, plus a washing machine conversion project, plus the future time I would save, the $1500 investment would be worth it in the end.

I was right! When I dried my first harvest of baby greens in my new/used Electrolux Greens Dryer, it was adequately dry and able to be bagged right out of the spinner! Note: overloading the dryer would lead to less efficient drying, but as long as I didn’t fill the basket more than ¾ full, it worked great for me.

Packing Table

To the left of the greens dryer was my packing table, just a standard six-foot folding table. It was equipped with my TORREY digital scale, along with my different-sized bags and twist ties for packaging. I’d lift the basket out of the dryer, and transfer the greens directly into their bags while sitting on the scale. The goal of the wash/pack station is to touch your product as few times as possible, eliminating any unnecessary steps or movements.

Cooler

When I first started the season I was just using an old refrigerator I picked up for next to nothing that I found on Craigslist. That quickly proved to be inadequate and I found myself typically having to harvest directly before a delivery. This was quite stressful and led me to fast-tracking my next project: The Coolbot Trailer! Look for a coming article on an in-depth description of that build-out!

Conclusion

Your wash/pack station will surely look somewhat different than mine based on your location, whether or not you own or lease, and what kind of infrastructure you already have (if any). Regardless, the basic components will always be needed: protection from the elements, a comfortable place to work, a hand wash sink, a place to wash roots, a place to wash greens, a greens dryer, a place to back, and a place to cool your vegetables until delivery. Ensuring all of these elements are in place BEFORE your first harvest can’t be stressed enough. I hope you found some value in walking through my DIY wash/pack tunnel setup!


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Seth Davis

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