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. Magnetic pumps