THE IRON-CLAD TRUTH:
Above ground, beyond compare.
AbovE GrounD Installation
For above ground DWV installations, there are three important things to keep in mind: support, expansion and costs. Spoiler alert: American-made cast iron wins on all three.
SUPPORT
Hanger support is critical for plastic DWV systems, as plastics do not have the structural integrity of cast iron. Plastic is impacted substantially by its environment and there are special considerations that must be taken into consideration. At the very least, the minimum requirement found in model code is that plastic must be hung horizontally with hangers spaced every four feet, compared to cast iron only requiring hangers every ten feet, within eighteen inches of each joint.
EXPANSION
Temperature swings affect different materials in different ways. Cast iron expands and contracts at a rate very similar to concrete and steel, which most commercial buildings are made of. This similar rate of expansion means that a cast iron DWV system moves with the building, without requiring any protective measures. Plastics, on the other hand, have a much different rate of expansion & contraction, requiring complex solutions such as expansion devices, offsets, loops and change of direction. Failure to compensate for this movement in a plastic DWV system may result in system failure and property damage.
COSTS
When you add up the extra materials and labor required to install a plastic DWV system properly and to code, you’ll quickly realize that cheaper material can truly cost you so much more.
The cost of hangers, anchors, connectors and extra labor in a typical plastic installation can be up to 2½ times that of cast iron in horizontal installations.
Resources
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CISPI Brochure
All too often, the perceived cost advantages of plastic over cast iron are not what they seem. This brochure will help it all make sense, by comparing six areas that can add cost and complexity: fire resistive construction, crush and deflection underground, thermal expansion/
CISPI Cast Iron Soil Pipe & Fittings Handbook
This newly updated handbook features the latest technical specs, installation guides, manufacturing details, layouts and other useful information for putting cast iron soil pipe and fittings to work for you.
CISPI 301
Standard specification for hubless cast iron soil pipe and fittings for sanitary and storm drain, waste and vent piping applications.