I made this basic tetrahedron with:
- 4 side outlet elbows (3 female 1/2 inch sockets 90 degrees from each other)
- 12 street elbows (male 1/2 inch through 90 degree bend then female 1/2 inch socket)
- 6 pieces of 1/2 inch pipe (all same length, here I used 12 inch lengths.)
- Put the street elbows at each end of the pieces of pipe.
- Put the male part of the street elbows into the side outlet elbows so the other two openings of the side outlet elbow are pointed away at 45 degree angles.
You can also use regular elbows or tees instead of street elbows. You will need a short piece of pipe to connect to the side outlet elbows (I used 1.5 inch lengths since the sockets are about 0.75 inches deep each.)