On Fri, 30 Jun 2006 11:10:57 -0400, "EXT"
wrote:

You need either a check valve, which I find often unreliable in sump
pump use because they often get stuck open, or

They get stuck open by dirt and junk in the water, I presumem, yes????

What about when they work ok. Does the valve take up any space inside
the pipe and slow down the expulsion of the water??

It seems like it must take up quite a bit, because if the valve plate
is a stiff plastic circle, just a bit bigger than the inside pipe
diameter at that point, how far open such a circle go? Not all the
way.

And if the plastic circle was smaller, that would mean the pipe
narrowed at that point, and that would be a restriction too.

In a check valve for plastic pipe, is the valve plate a stiff plastic
circle?