Steel Pipe in Ductile Iron Network

[thamightymax]

I was reviewing a water treatment plant that had 4 sand filters and saw that all the connecting piping was ductile iron except for 1 section of steel pipe (8"). The section of steel pipe was a straight run that bolted to 45 deg D.I. fittings on each end. It was locat not far past the sand filters. It was on the clear water side headed to the clear water tank. What is the reasoning for this one section of steel pipe?

Thanks

 

[bimr]

It was probably a missing piece and it was quicker and faster to make the piece out of welded steel than to special order a ductile iron piece.