About a year ago I attended a national engineering conference, with a presentation wherein a presenter mentioned “C900 fusible pvc” pipe. After the presentation, I heard a consultant engineer from the audience make a comment to the assemblage that fusible pvc did not meet AWWA C900 “formulation”. I do not know why the consultant made this comment, nor even what exactly what he may have meant with this specific phraseology; however, I wrote the comment down (as this gentleman was not challenged there by the presenter, nor anyone else in the audience). When I got back to my office, I did check my copy of what I thought were the latest versions of the C90X standards. While there was a reference to fittings fabricated by solvent cement or butt-fusing/weld, I couldn’t even find any specific reference to fusible pipe joints or fusible joint pipe. While this consultant’s comment seemed strange under the circumstances and perhaps has since been addressed [in that the manufacturer appears to have even somehow (or for some reason?) trademarked the standard alphanumeric designations into their product names!], if conformance to a minimum consensus standard like AWWA is important to you or your firm, you may at least wish to ask the manufacturer for a certificate of compliance to all aspects of the applicable standard.
Otherwise, there also appears to be a perception (being cultivated by some plastic pipe manufacturers and manufacturers/providers of fusing equipment and services) that gasket joints for pipelines in general are somehow bad or inferior. In my opinion, it is indeed generally undesirable when any pipe or joint that is made up in the field, and I’ll note that includes fused or welded connections (that in spite of the spin are nevertheless “joints”), leaks. However, when properly assembled it would appear at least most contemporary good quality joints do not leak, and in particular I think at least good quality flexible, rubber-gasket joints may well also offer some arguable, long-term technical advantages over more rigid/welded systems. Is it possible these arguable advantages in some cases may include a general ability to assemble in virtually all manner of varied weather/conditions with available local/simple tools, equipment and less than very highly skilled labor, as well as a function of space etc. in the sockets a subsequent (three-dimensional) ability to accommodate/provide relief for some degree of differential settlements or other ground/pipe movements, thermal excursions/movements, Bourdon and Poisson effects of pressure and temperature excursions etc., and all maybe without additionally/significant stressing and/or fatiguing the pipe walls (or lateral service etc. connections to the piping)? Is it also possible that the future long-term performance of on the other hand more rigid systems like welded et al may be some more uncertain, as I believe the bulk of “C900” pipe experience since 1975 is with gasketed joint pipes? In this regard, I noticed in the 1989 version C900 standard even made a specific comment in the Foreword that “Provisions for solvent-welded joints throughout the standard were deleted”. At that time this appeared to be a deliberate distancing from solvent welding and any baggage it might entail. (However, I’ve since noticed solvent welding has apparently been sort of resurrected in some more current standards, at least in the area of cheap fitting fabrications.)
Maybe these comments will prompt some further input from more learned folks that will enlighten us all.
