igor said:

"Puff Griffis" wrote:

o 4" is good. 5" is gooder. 6" is gooderer.

This comment is not to you so much as to a number of people here who say
that bigger is better with ducts. I can see that as a general proposition,
but at some point, relative to the size of the fan, won't velocity suffer
in a significant way? And, doesn't velocity have a role to play in an
effective DC system? After all, we are not just talking about air -- also
talking about moving solid waste. Or, as is sometimes the case, am I
missing something here? -- Igor

You are correct. When velocity drops too low, you cannot maintain the
material in suspension - it just builds up in the pipes instead of
flowing to the DC/pre-collector.


Greg G.