> Ken wrote:
>
> > The spring loaded ball valve will be to restrictive, better with a
> > flapper valve.
>
> And Rusty responded:
>
> The listed "CV" rating is defined as: "the amount of water (in gpm) that
> will pass through a fully open valve at 1 psi with 1 specific gravity (60° F)."
> Since the rating for the 1.25" valve was 44, and you'll have one of these for
> each pump, it seems reasonable to me.    

Yeah, sorry, I should have mentioned that. These things will pass way more water (44gpm) than the EWP can pump (88lpm), and that's only at 1psi. The formula to calculate the actual value is:
  gpm = Cv * sqrt(pressure drop / specific gravity)

The specific gravity for water is 1, so at 1psi you get Cv * 1, or Cv. At higher pressures you get more.

You SHOULD know that it does impose a small amount of flow resistance, but certainly much less than a right-angle bend so it's probably not worth even calculating.

By the way, their Web site does note that for this particular swing-check valve, it should be mounted horizontally, or if the flow is vertical, it should be mounted so that the flow is UP. That may matter to you depending on how you arrange your plumbing.

Regards,
Chad