You can look at the pipe friction head loss chart shown on this site to see
what the differences in head for different pipe diameters and calculate the
anticipated flow rate. http://www.aquaart.com/pondFLC.html

RichToyBox
http://www.geocities.com/richtoybox/index.html

"Grumpy" wrote in message
news:_veWc.72162$TI1.30000@attbi_s52...
How much difference will there be between 2 and 3 inch pipe? I'm trying
to do 3 inch flexible pvc pipe all through out. One problem I am for
seeing is that one of the filter's I'm planning to use only has 1 ½ inch
ports (aqua ultima II). Take a look at the bottom of the page of my
schematic so far. It just seems that 2 inch stuff is more available.
Thanks