Just how strong is a milk crate?

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Video shot this morning. Probably should have done it a few months ago before I bought 400 of them. Pasted from YT description:

The answer is: Probably strong enough for anything you can imagine putting on it. I'm no engineer, but my redneck math tells me these things are shockingly sturdy.

I'm building a cistern for a man-made pond and the design required me to find a way to store about 3000 gallons of water underground.

The "go to the store and buy it" solution to this problem in the pond world is a product called a water matrix block, also known as an aquablock or soakaway crate.

But those are REALLY EXPENSIVE! As I write this, they're more than $2/gallon of storage. I looked into all kinds of other possible solutions like plastic pallets, culvert pipes, industrial storage totes, rainwater tanks, and other oddball products I could re-purpose.

But the solution I kept coming back to was milk crates. They're cheap, relatively easy to come by, and—as I just learned—STRONG AS HELL!

I bought 400 of them from a pig farmer (yep, really!) and this is a video of me punishing them to see what they can take.

 
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Thanks. I wish there was a prize at the county fair for best boulder—I have a few good ones!

I’ve read the same for aquablox—5500 lbs/sf. Don’t know how they tested, though.

Farmplast—who sells bulk milk crates to the public—has an engineering report on their site with pictures. Their testing showed about 2,500 lbs/sf before the crates became visibly stressed. It's pretty remarkable for some cheap, flimsy plastic. And if you backfill against it, it will only get stronger.

For me, it's just a matter of "how much strength do you really need?" All the hand wringing about "oh, it's not as strong as a real matrix block" and "matrix blocks are specifically designed for ponds" seems pointless for most DIY pond builds. If you wanted to, you could custom engineer your own matrix block that could safely hold 50,000 lbs/sf and costs $20 per gallon of storage space. But why? I'm using some pretty giant rocks, and the milk crates—which cost about $0.30 per gallon of storage are more than enough. Aquablox are over $2/gallon.
 

TheFishGuy

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Thanks. I wish there was a prize at the county fair for best boulder—I have a few good ones!

I’ve read the same for aquablox—5500 lbs/sf. Don’t know how they tested, though.

Farmplast—who sells bulk milk crates to the public—has an engineering report on their site with pictures. Their testing showed about 2,500 lbs/sf before the crates became visibly stressed. It's pretty remarkable for some cheap, flimsy plastic. And if you backfill against it, it will only get stronger.

For me, it's just a matter of "how much strength do you really need?" All the hand wringing about "oh, it's not as strong as a real matrix block" and "matrix blocks are specifically designed for ponds" seems pointless for most DIY pond builds. If you wanted to, you could custom engineer your own matrix block that could safely hold 50,000 lbs/sf and costs $20 per gallon of storage space. But why? I'm using some pretty giant rocks, and the milk crates—which cost about $0.30 per gallon of storage are more than enough. Aquablox are over $2/gallon.
This is impressive! They are so much cheaper, I think they are just the way to go.
 
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I've been price comparing milk crates. If you only need a few, tractor supply or duluth trading company is the way to go. But anything over 48 pieces go with FarmPlast
 
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I've been price comparing milk crates. If you only need a few, tractor supply or duluth trading company is the way to go. But anything over 48 pieces go with FarmPlast

Yeah, Farmplast is great for new, but the real deals are on used crates on CL and FB Marketplace. If I were buying brand new, I’d probably go with large culvert pipe. Maybe plastic pallets.
 
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If I was closer than 4 hours to a major city I would definitely go via cragslist or FB market. I'll have to look into the pallets. The septic leach field culverts seem price prohibitive, I might as well get an aquascape centipede for that.
 
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I know they’re incredibly strong. But my question is for how long? In my opinion, the plastic is going to fatigue eventually. But when, dunno.
 
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I know they’re incredibly strong. But my question is for how long? In my opinion, the plastic is going to fatigue eventually. But when, dunno.

We shall see! I think with a lot of weight on them, they worked slowly crumple over the years, but by backfilling and locking them all together, They should last much longer.
 
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One other issue with milk crates is if they are made from what type of plastic. The aqua blocks are all made from food or water grade plastics. and that could be a big deal if the plastics from a misc "milk crate is not" i believe they stacked 9000 ponds on one aqua block. Id not use milk crates it i was to drive over the area
 
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Id not use milk crates it i was to drive over the area

I was going to say the same - which is probably highly unlikely for most builds, but something to consider if you think you might EVER need to drive over it.

As for food safe - who knows, but I have no idea if Aquablox are either to be honest.
 
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I would definitely never build with milk crates or pallets if I were going to drive over it. Of course, if you bury it deep enough, probably could work. Like Lisa said, pretty unlikely need for most back yard builds.

As for food safe... I don't know. I don't remember seeing anything about aquablox being nsf certified, but if they are, yes that would be a consideration if you were planning to use them for drinking water. Again, doubt that's a big concern for back yard ponds.

The biggest knock on milk crates is that they're just kind of hard to find used in bulk. Plastic pallets seem much easier to come by.
 
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yes that would be a consideration if you were planning to use them for drinking water.

Plastic leaching can affect fish, too. The amount of plastic in our waterways, beaches, wild fish, and IN US is kind of terrifying. But even food safe plastic can leach, or so I've been told.
 

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