Big pipes have less resistance to water flow then smaller pipes.
Water travels through the pump a lot faster then you want to
push or pull it through the pipes. The larger pipe diameter allows
the water to flow at a slower (less friction) pace.

The only downside to a larger pipe diameter is that if you slow
the water too much solids might settle out on the bottom of the
pipes. I doubt that this would be a problem given any reasonable
pump selection.

Howard

"BenignVanilla" wrote in
message ...
"John Hines" wrote in message
...
snip
Some of that depends on the parts you select. IE I've seen in pond
skimmers, that hook up to inch and half. Kinda a waste to run 4 inch
pipe only to neck it down that much, since most pumps don't take that
either.
snip

So what you are saying...that my plan of run all my pipes and figure on a
pump later could be a bad idea?

BV.