PVC pipe sizes

Here are some PVC pipe sizes available in Australia

These tables come from the IPLEX website. Vinidex list the same sizes, but no additional ones.
The highlighted rows are sizes that have been used in projects on this site.

All measurements are in mm

DWV - Drain, Waste and Vent, commonly known as Sewer Pipe

PVC-U - commonly known as Stormwater Pipe

In Australia, the 90mm stormwater comes in grey, green or white. The green is the recycled product, and is becoming more common. The grey looks better, so it pays to ring ahead to see if it's in stock

If you a confident that you will only be building one speaker, you can buy short (1metre or 3m) lengths of some sizes from Bunnings.

If you have the merest suspicion that you might build others later, I would suggest you buy a full length (6m). Usually, the best place to buy it is from the trade desk of your local plumbers supplier, although the most recent lot of 6inch pipe would have been cheaper at the local hardware store, so shop around!

The most recent prices I paid at the plumbers suppliers were:
$22.00 for 6m of 90mm stormwater. (April 2008)
$36.00 for 6m of 100mm sewer pipe (May 2008)
$87.80 for 6m of 150mm sewer pipe (July 2009)      $76.25 at local hardware store (July 2009)

The larger sizes can be very expensive - I had to buy a 6m length of the 225mm pipe for $160aus, back in 2005, and that was trade price! If you know any plumbers, you might be able to scrounge an offcut. Last time I looked, the going rate was a carton of beer, which is good value!

By way of comparison, here are some recent Bunnings prices. Note these are sold in shorter lengths, price shown is for 6m