PVC Pipe Between Cast-Iron Pipe

[Yacub]

Hi,

I'm looking to replace a short section of 12" cast iron pipe (install year 1974) with C900 PVC (approximate length 2.8 feet, flange-flange connections). The section in question is severely corroded as it is the location of our sodium hypochlorite injection that has leaked in the past. I would like to use PVC because it less susceptible to corrosion in the event of future leaks (also having the injection quill at 90 degrees from top instead of on top). Has anyone had experience mounting PVC between two sections of cast-iron pipe? My primary concern is that the PVC will expand compared to the cast-iron, potentially causing pre-mature failure due to stress.

 

[bimr]

Is this a buried section or above grade section?

 

[Yacub]

It is currently half buried, half in a vault ~ 3 feet to top of pipe. The finished product will likely all be in an expanded vault. Located in an area with temperatures ranging from 10F to 110F. Assuming a range in the vault of 30F to 100F, I calculate a stress of 716 psi due to temperature variation, which falls well within the 7000 psi tensile strength, but i couldn't find any references to any compressive strength.

 

[hydrae]

There are a variety of flex joints available (ball-socket, rubber spheres)
even just a dresser coupling can provide enough flex to keep the PVC from breaking
but any flex joint will need to be evaluated for thrust

Hydrae