Look for an industrial pipe supplier such as EMCO, Wakefield Sperling, or Bartle and Gibson.

Can also check 'Irrigation' and 'Plumbing Supplies, Commercial' in the yellow pages.

Obviously some of these are fixtures and other stuff but you'll hit what you want here: http://canada411.yellowpages.ca/searchBusiness.do?action=homeSearch&start=1&srchty pe=category&Se=smp&directoryId=093402&provinceId=O N&cityId=RICHMOO1&categoryName=&showMsgBox=1&wha t=Plumbing+Supply&Dir=093402&sType=simpleSearch&st ep=find&categoryId=01031200&city=Richmond+Hill

 

Oh and I thought I saw some 6" at HD or Rona but it may have just been fittings and not pipe [img]graemlins/dunno.gif[/img]