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Related to How do I separate 2 drinking glasses that are stuck?, but also quite different. Sometimes I have some plastic five gallon buckets stacked up (usually 2 or 3, sometimes 4) for storage, and they slowly sink together. I might not need them for years. Then when I do need them, I can get them apart, but at some expense:

  • If I poke a nail-hole in the bottom of one, it will release the vacuum, and the bucket will come away. Not good if you intend to use the bucket for liquids, like I usually do.

  • I can get the air compressor, plug it in, wait for it to pump up, find a hose and fittings, put them on, jam the end between the buckets, and blast in some air. They pop apart nicely. However, the air pump isn't always in working order, and sometimes I have this problem in places where the folks don't have a compressor.

  • Holding the buckets between your knees firmly, and twisting the top one. Doesn't work on tight buckets. You can do this for 1/2 hour sometimes to no avail. Same with the method of rolling the buckets, squashing them a little, rolling them, squashing them again, etc. It works unless the buckets are real tight.

  • Getting a narrow steel rod and jamming it between the buckets to let in some air. It works also, but I avoid it as it deforms the buckets.

I'm not sure if there are any conventional methods, because this isn't really supposed to happen. Now you know my problem, and the methods I've tried, and why they weren't satisfactory. What is an efficient way to get multiple five gallon buckets un-stuck that doesn't involve taking a long time (20 mins or longer is a long time), and doesn't involve deforming/defacing the buckets?

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7 Answers 7

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As you've probably figured out by now the reason the buckets are so hard to separate is the vacuum, or negative air pressure, that forms when you're trying to pull them apart.

enter image description here

By applying force trying to pull them apart you create more negative pressure making them even harder to pull apart.

So now that we understand why this is difficult... What can we do about it?

You could try to equalize the pressure by warming the buckets and the air inside, in theory this may work. As the air molecules heat up they begin to move faster and bounce against the buckets more reducing the negative pressure slightly. The down sides to this approach are obvious though, heating the buckets will also cause the plastic to expand which may make separating them more difficult and heating the buckets isn't always easy.

As mentioned you could try to lubricate the buckets as you pull them apart, once again this may work, and once again it has downsides. Even though the lubricant may reduce friction it makes the vacuum problem slightly worse because you're filling the space that could have allowed air to pass through.

After some experimentation I've found that rinsing the buckets with water and applying a little pressure and being patient may be the best method.

More specifically:

  1. Spray down the buckets inside and out with plain water, mostly to clean them, but it may provide some small amount of lubrication.
  2. Wedge a flat head screwdriver between the top edge of one bucket and the rib of the next. enter image description here
  3. Gently turn the screwdriver and wait a second for the pressure to equalize. enter image description here
  4. Rotate the bucket a couple of inches and repeat steps 2 and 3

After going around the bucket, you should be able to slowly pull the buckets apart.

Once you have your buckets separated you can prevent them from sticking in the future by placing a piece of cardboard or folded paper between the walls of the buckets when you re-stack them.

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  • Good answer, and especially the good suggestion for preventing the problem by inserting a piece of cardboard or folded paper between buckets. That is good advice both for those in the process of storing buckets, and for those having some buckets stored already which can be redone to prevent further issues.
    – holroy
    Commented Feb 14, 2016 at 0:31
  • Before you stack, cut a 2" or larger PVC pipe into small sections. You'll have to experiment since buckets aren't exactly the same size. Drop a piece in before stacking the next one - cut the sections just large enough to keep the next bucket from stacking tight - should stop the next one with a little gap.
    – Blackbeagle
    Commented Jan 9, 2017 at 20:17
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Your third bullet point (Holding the buckets between your knees firmly, and twisting the top one.) is a good start. Do this, but drip soapy water between the buckets as you go. This will help loosen the seal and therefore break the vacuum.

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Tie a brick or other large weight to the outermost bucket with a strong cord. The cord should be looped around the body of the bucket so the weight hangs off to one side, and beneath. Hang the innermost bucket up by the handle. Wait several minutes and the stack of buckets will separate. Do this repeatedly until all are separated.

If this doesn't work, tie another weight to the other side, again looping the cord around the body. Increase the amount of weight hanging from each side. The stack will separate.

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  • Hm, that would work, but not sure how fast.
    – J. Musser
    Commented Feb 16, 2015 at 20:13
  • Bigger weights, faster result, until the handle pulls loose.
    – subjectivist
    Commented Feb 16, 2015 at 20:22
  • Yeah, logically. If I use a 50 lb dumbbell, how long do you think it would take?
    – J. Musser
    Commented Feb 16, 2015 at 20:25
  • Well, a different type harness would be needed for one weight to hang directly beneath the outermost bucket, which can easily be made. If all is in-line, with a fifty pound weight I guess three minutes, most.
    – subjectivist
    Commented Feb 16, 2015 at 20:28
  • So more tome would probably be spent rigging it up/finding some free rope - I'll have to try it sometime
    – J. Musser
    Commented Feb 16, 2015 at 20:30
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the hot water theory works but it's HOW you do it..put the buckets in a laundry sink or attach a hose to the hot water heater..wet the outside of the EXTERIOR BUCKET,, rotating it in the sink to get it completely heated,, top to bottom,, about 15-30 seconds,, take the buckets out of the sink and pull on the INTERIOR bucket.. should slide right out..I just did it with 4 of them..just pops the vacuum like nothing,,

All the best peeps! we make a great team!

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What I would try doing is a solution mentioned in the question you linked:

Hot water and ice water. Submerge the bottom glass or bowl in very hot (but not boiling) water. Fill the uppermost glass or bowl with ice water. Presto! The simultaneous expansion and contraction of the layers should unstick even the most stubborn glassware.

I've tried this before with smaller buckets, and it worked. Good luck.

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  • 3
    Plastic is easily warped and has lots of surface friction. I could try it, but I doubt it will be time effective.
    – J. Musser
    Commented Dec 31, 2014 at 17:46
  • You'd have to have a container larger than a 5-gallon bucket for this to work. Not to mention heating it up.
    – GimmeTehRepz
    Commented Dec 31, 2014 at 17:49
  • It usually depends on the brand of bucket. Usually the plastic used is more durable than standard plastic.
    – James Lynch
    Commented Dec 31, 2014 at 17:49
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If the buckets have handles, try turning them upside down and stepping on the handle of the inside bucket. Grab the collar of the exterior bucket, twist, and pull. This is basically the "pull really hard" method but using your weight to hold one down makes it much easier.

If you have a friend handy, you can each grasp a bucket while twisting / pulling. This is another variation of the "pull really hard" method but it requires friends and who has time for those?

If you don't have handles or friends, you can try the inverse of the "cold water bath" by pouring hot water in the interior bucket and rotating it to get as much coverage as possible. If they're heavy-gauge plastic, this method may require really hot water or just plain not work. You could also try to get some soap down between the buckets but now we're to the point of creating a lot of cleanup once they're apart.

You already know that it's all about breaking the vacuum. I've used wooden shims, flat head screwdrivers, and metal yardsticks in the past but that was with pickle buckets and they're pretty lightweight.

If you have no handles or friends or hot water or soap or screwdrivers, then I say give up and go get ice cream.

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I've done the air pressure into the sides of the bucket and it has worked - started with a needle valve for inflating sports ball, which loosened it just enough to stick a little bit larger tapered valve for inflating vinyl rafts.

On the prescriptive side to avoid getting them stuck, I wrap the buckets with two layers of 2" wide duct tape just below the bottom anti-distortion ring and embed three equally spaced pieces of rigid wire between the duct tape wraps. I like to use #12 insulated electrical wire and I cut them at about 1-3/4" so they don't extend beyond the tape. Takes just 1-2 minutes per bucket to do, but keeps the them from fully nesting and maintains an air gap to avoid the vacuum seal. You can push them in slightly to nest them for carrying. You gain about 1" height per bucket when nested.

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