Check out the "hub less couplings" in the local plumbing supply, Lowes, or Home Depot. You may find something that works for you. I'm using a Dust Deputy connected in line with a whole house central vacuum unit to pick up saw dust from the floor, my scroll saws, drill presses, and sanders. The central vacuum unit pipes and the Dust Deputy fittings are coupled together with these rubber "hub less couplings". I'm not certain, but I think I used the 2" size for my Dust Deputy, which is the smaller clear plastic model.. They fit tight, but did go together. There are many sizes of these, and even ones that adapt one size to another. The stainless hose clamps that come with them will allow you to shrink a loose fit enough to make it tight, but the ones that I chose fit tight before tightening the hose clamps.
With a Dust Deputy attached to a 5 gallon plastic bucket you may have imploding problems where the bucket walls collapse inward from the high suction. I had serious problems when I began using the central vacuum unit as my vacuum source with my Dust Deputy connected just ahead of it, because my buckets collapsed almost immediately. I then learned that the Firehouse Subs Pickle Buckets available from Firehouse Subs for $2 each were supposed to be stronger than the commonly available white buckets, so I bought a couple of them. Everything was working OK until a wood chip plugged the end of the vacuum hose (I was vacuuming the floor). Almost immediately, I heard my Firehouse Bucket collapse from the increased vacuum level. I studied the problem for a while and then realized that the the top 1/3 of these Firehouse buckets were ribbed on the outside. The white buckets were not ribbed at all. Then I figured out that if I stacked 3 Firehouse buckets together, that there would be ribs all the way to the bottom of the top bucket and the total bucket wall thickness would be 3 times the thickness of just one bucket. I did this, and never had a collapsing problem afterward. The only problem with using these
cheap Firehouse Subs pickle buckets is that if you vent your dust collector vacuum inside your shop, you may suddenly need to go get a hamburger to go with the un-mistakable aroma of good dill pickles that will quickly fill your shop. I have tried many methods of getting the smell out of these buckets. Some worked a little and some worked better, but none worked completely. Putting the open buckets and lids face up in the bright Sunlight for about a week seemed to work the best, but it still wasn't 100%. I vented my vacuum outdoors shortly after I began using the pickle buckets, so I no longer had the desire to get a hamburger after that.
I have since found a 20 gallon steel grease barrel and made a wood top for it out of two layers of 3/4 cabinet birch plywood with the Dust Deputy attached to a hole in the center of both layers. The lower layer just fits into the open end of the barrel and the upper layer is 2" larger in diameter. I caulked and glued these two layers together. Then added some 3/4" wide closed cell foam Weatherstrip to the underside of the top layer right next to the smaller diameter layer. I had a perfect seal on the first try. At my present amount of sawdust creation I can go about 4 months to 3/4 fill the 20 gallon barrel. When it needs to be dumper, there is enough flex in the pipe connections to allow the lid to be lifted and the barrel removed, dumped, and replaced.
I can't find a photo of the three stacked pickle bucket vacuum system, but did find two photos showing what happened to the single Firehouse Subs bucket. The third photo is of my central vacuum, Dust Deputy, and 20 gallon grease barrel the way that it is today. Since my shop is small, it resides in the attic of my shop with vacuum lines and inlets located in several places in the shop, plus one in the outside wall, so I can vacuum my cars and trucks with it..
Charley