Example sizes

Here are some example concentric vent arrangements

These examples show the closest you could get with PVC Pipe sizes in Australia. The middle column shows the required figures as per the full equations, using the calculator. The right column shows what PVC pipe could be used

The slight mismatches in CSA may or may not be audible - only an experiment will tell.

Example1

Inner tube diameter
51
use 50mm sewer ID-51 wall-2.2
Middle tube diameter
75
 use 75mm stormwater ID-71.8 wall-1.6

Outer tube diameter
94
 roll your own ID-94
Inner tube end gap
12
Middle tube end gap
8

Example2

Inner tube diameter
104
 use 100mm sewer ID-103 wall-3.5
Middle tube diameter
151
 use 150mm sewer ID-152 wall-4

Outer tube diameter

190
 roll your own ID-190
Inner tube end gap
25
Middle tube end gap
17

 

Extending this arrangement to 5 layers....

Adjusting thickness of tube3 to be 8mm causes layer4 to become an available size

Example3

Inner tube diameter
104
 use 100mm sewer ID-103 wall-3.5
tube2 diameter
151
 use 150mm sewer ID-152 wall-4

tube3 diameter

190
 roll your own ID-190 wall-8
tube4 diameter
231
 use 225mm stormwater ID-230 wall-5
tube5 diameter
263
 roll your own ID-263
tube1 end gap
25
tube2 end gap
17
tube3 end gap
14
tube4 end gap
11

As you can see, it is likely that you will need to make some of the tubes yourself. I favour using 2 layers of PVC pipe as per the composite tubes page, however you're only limited by your imagination!

If using sheet metal, be wary of the potential for the sharp end of the tube to act as a whistle. It may be neccessary to roll a double layer, filled with expanding foam, with an MDF end ring having a rounded profile

There may also be plastics that have the combination of rigidity and flexibilty to form a tube, with a thickness suitable for rounding of the ends.

 

The next page is a Gallery of steps to build a concentric port

 

Last update to this page 20/07/06

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