The old 4 port plenum: the whole system takes up a lot of floor space, which is precious at our house.   The motor/impeller and plenum were on the floor with the 4 hoses looping up and hanging from the ceiling with bungie cords supporting them near mid point.   Each hose has a blast gate on the equipment end, which is inconvenient (since the gate is behind most equipment) to read or switch.  

The 4 port vacuum plenum as it normally is seen.   This was replaced by the 4" Overhaul.

One of the 3/16" wing nuts.   Note the Gorilla Glue on one of the 4" nipples on the top, I cut a clearance hole for each nipple, inserted the nipple and caulked it.   Later they started working loose so I started using Gorilla Glue, it seals any air leaks and holds nicely.   The nipples are actually 4" couplers sawed in half.

Vacuum plenum open.   Note you can see the impeller of the DC-1100C and the chip bag to the left and behind the plenum.   This is how it looked when I opened it, virtually no dust build up after years of operation.   Note the duct to the impeller doesn't protrude into the plenum, same for the 4" input ducts, this reduces turbulence.

One of the hanger bolts.   You can see a few metal chips from vacuuming around the drill press.

The side of the plenum, you can see the heavy (3/4" plywood) front lid and back.   The entire plenum is held in place by the vacuum.

The back of the plenum up against the DC-1100's impeller housing.   Note the extra 3/4" spacer I had to add so the mouth of the 6" inlet (protrudes about 1 1/2") would be flush with the inside of the pelnum's interior to cut down on turbulence that would create dust piles inside the plenum.

Hoses above the plenum.   Some of the tools have moved around so I probably need to reassign the order.   Each hose has a blast gate at the machine (other) end. When I get some time, I'm thinking of replacing the 4 port plenum with a 6" hose to the ceiling and making a long plenum (like a pipe organ wind chest) with 4" drops spaced down it's length instead of the 4 hoses now used.   The down hoses could be shorter and still allow the movement I have now. Please see the 4" Overhaul<\a>.   I moved the whole 4" DC system to the ceiling and added a new 5 port plenum, cleaning up this tangle of 4" hoses.