If you have a burning desire to make your own buried cache tubes, you might get some ideas from what is involved on our end.

No, you can't. For a 4-inch-diameter tube you can get most of your materials at Home Depot or Lowe's but for 6-inch and 8-inch diameters you will have to buy from a plumbing supply store that will probably have to special-order the parts you need.  The larger diameters are infrequently used and quite expensive as the table below shows.

Why an 8" plug should cost over five times as much as a 6" plug is a major mystery.  Unbelievably, the first one we priced was $47.47!  After looking at the sky-high prices for 12" tube parts we decided not bother making any.

Here are some other things you will need to make an unpainted 6-inch-diameter tube. We've listed our costs per minumum order, including shipping where applicable, but you can save money if you can obtain smaller quantities.  We've left out a few things we use that will be easy to substitute, adult-size toungue depressor "spatulas" for instance:  We'll pull together more figures for this list soon.
PVC primer                                                           $10.78
PVC cement                                                             9.80
PVC board for lug wrench  (5/4" x 6" x 20')                 55.65
Mylar Bag Liner (10 minimum)                                  45.38
7" Cotton Tubing (order by the pound)
Cotton Parts Bag (100 minimum)                              25.45
Pouches 100cc O2 Absorbers (15 minimum)             83.51
Wax Thread Sealant                                                 1.49
Polypropylene cord                                                   2.87
Alcohol Pad (Lens Wipe 16 pack)                                .99

Of couse there are other items you will need that you may already have:
Saw to cut your pipe to length
Jig saw or router to make square hole in lug wrench
Drill and bits to bore cord hole and starter hole in lug wrench
Rags and acetone to clean up with
Sander or sandpaper to smooth inside and outside pipe edges
Compressor & air hose
Pressure gauge, air fitting, air valve, extra plug, teflon tape

We pump 5 lbs. air pressure into each BURY 'EM! tube with an air compressor to make sure there are no leaks along the glue joints.  The 4" and 6" tubes are submersed in a tub to check for escaping air while the 8" tubes get a sudsy water treament around the glue joints to check for bubbles forming. These are the pressure test plugs for the 4" and 8" diameter models, showing the arrangement of guage, valve, and air fitting.  The male threads are heavily wrapped in teflon tape.

Caution:  Do not overpressurize.  We had an overpressurized 8-inch model blast its plug out, which tore a hole in the ceiling and could have made a mess of someone's face, maybe even killed them.  
   
 

   
   
   
  
Each diameter of pipe has its own wall thickness, increasing as the diameter increases. Here are nesting 4", 6" and 8" diameters.  The smallest happens to be the largest size available in most building supply stores including Lowe's and Home Depot.  The 6" and 8" pipe may be available at a plumbing supply store but the fittings you need will probably have to be special-ordered.   
   
   

The end edges of the pipe are exposed inside the tube and could cause wear and puncture of the sealed Mylar liner if not smoothed.  Don't overlook this detail.

We also bevel the outside edge to make glueing on the fittings easier.  Slight edge irregularities can otherwise prevent speedy joining, requirng you to re-glue. The cement thickens rapidly as it softens the underlying PVC. This requires quickly wetting both joint surfaces with primer, speedily applying lots of glue to each surface, and joining the pieces, giving a quarter-twist, all in under ten seconds.  For 6" and 8" diameters this cannot be accomplished with a small dauber, which is why we buy quart cans of primer and cement.  Smaller cans have daubers that are too small.

When you join two glued pieces you will have to press hard and hold them for a few seconds to prevent the fitting from creeping part-way off the pipe.  (We're not sure why they tend to creep like this but they do.)

     
     
    
You won't need to paint your buried cache tube but you might benefit from painting your pipe clamp that is used as handles for tightening and loosening the threaded plug as it is held in place with the lug wrench.

First we clean any oil from the clamps, bolts, and nuts with paint thinner, then give them a second bath in acetone prior to applying a coat of automotive primer.  When dry to touch we apply a coat of flat enamel.  This treatment will slow down rust formation but, to be honest, we painted them for looks.