Technical Blog

Question – one question that I hear quite often about testing of installed PVC pressure pipe is: “What is the maximum test pressure I can use?” Answer – since every component of a pressure pipeline has a pressure rating, the simple reply is: Do not exceed the pressure rating of any of the pipeline components.

In July 2016 a study was published titled “A Framework to Evaluate the Life Cycle Costs and Environmental Impacts of Water Pipelines.” The study, funded by the Ductile Iron Pipe Association (DIPRA), “aims to develop a Pipe Material Life Cycle Assessment tool (PMLCA) that is capable of analyzing different pipe material scenarios and suggesting the best option to the various decision makers.”

Questions sometimes arise about which way the bell should be positioned in a PVC pipeline. Typically there are two concerns: 1. Does bell direction make a difference in pipeline hydraulics? 2. Does it make a difference during installation?

Occasionally I hear a report about safety issues with air-testing of sewer pipes. The story usually starts with “An end-plug let go.” There was a sudden whoosh of air out of the manhole that had potential consequences for nearby personnel.

There are many different outside diameter (OD) types used for PVC pipe for various pressure and non-pressure applications. Not only are there several OD types, there are also associated abbreviations to add to the mix.

PVCPA has recently published a new document titled, Design and Installation Guide – PVC Fittings and Laterals for Solid-Wall PVC Sewer Pipe. The guide provides information on appropriate system design and proper installation of PVC fittings products where solid-wall PVC pipe is used in non-pressure applications.

The Ductile Iron Pipe Research Association promotes ductile iron as “stronger” than PVC. While it is true that side-by-side laboratory testing would give the nod to DI, laboratory strength does not always transfer to real life.

The PE industry has developed a new pressure-pipe material that has been described as “high-strength.” Although the words “high-strength” sound reassuring, the reality is that pipe made from PE4710 is anything but.

Plastics have a material property that sets them apart from the traditional materials that most engineers studied in school. For traditional materials, there is no distinction between short-term loading and long-term loading – the material responds the same in either case. For plastics, however, there is a significant difference: plastics can handle much higher short-term loads than long-term.

Attached is a two-page material comparison sheet that addresses some important issues in sanitary sewer pipe selection. The document also serves as a quick reference for comparing PVC and PP non-pressure pipe.