Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net> Hi Adam, 6 inches or less is fine. That leqves about 1 inch between the primary and secondary. Cheers, Terry At 07:11 PM 2/7/2002 -0500, you wrote: > > my primary is 8" at the beginning and i was wondering how big of a pvc pipe i > should use for my secondary. I am thinking 4-5" > Thanks!! > Adam