Does anyone know a good source on the web for accurate equivalent lengths of pipe fittings. I have searched & located several sites, but they all seem to vary significantly & especially compared to sample values in my mechanical engineering reference manual.  I especially want to know the equivalent length for 4" & 6" ball valves.

p.s. I do not have name plate data to contact the manufacturer for the Cv values either. If you do not have the valve nameplate data then any estimate is as good as any other, particularly if you have reduced bore valves. There is no guaranteed consistency in reduced bore ball valve internal dimensions from one manufacturer to another.

For generic estimates involving commercial steel pipe I would use L/D = 4 for a full bore ball valve and L/D = 25 for a reduced bore valve.

Ball valves of identical dimensions would have virtually identical pressure drops whether they were made of steel or plastic, but the associated piping could have somewhat different pressure drops per unit length depending on the material.  This would of course have an effect on how you express L/D. Anyone have any thought to my previous question: "I have a simple pipe system of primarily 6" pipe with some sections of smaller diameter branches (see attached sketch) that are of short length.  Should I even bother to convert these short-length sections to the 6" diameter equivalent?"

There are 6 branches or approximately equal length - 10'. There are four 4" branches and two 3" branches (which reduce to 2" for half the length).  The total length of the 6" straight pipe alone is well over 250'  (not including equivalent lengths for 6" fittings).
Sweage pumps &Sludge pumps