JPMacG

My point is that from the standpoint of other electrical technologies (such as RF circuits), the system we call single phase could well be called two phase. What else would a two-phase system be? Hint: whatever it is, it the two phases need to have a 180 degree relationship. Would it make you feel better if the phases were created using two separate secondaries connected in series? How about two separate transformers with their primaries in parallel and their secondaries in series? Either would produce exactly the same phase angle characteristics as we get from our "single phase" service. Sorry to belabor this silly discussion, but please don't criticize others for using non-conventional but equally correct terminology.

Convention is to describe standard residential service as single phase but there are certainly legitimate arguments in calling it either single or two phase. If one looks at the waveforms with a dual-trace oscilloscope, with the probe grounds on electrical ground and one probe on each hot, the oscilloscope will display two phases. The obsolete system known as "two phase", which was used in the subway system in Philadelphia among other places, might more accurately be called a degenerate 4-phase system. It is really two independent "single phase" circuits with a relative phase of 90 degrees. I recently went through this argument with one of my company's electricians. He was mocking the company RF circuit design engineers for their terminology. I explained to him that his terminology, while the convention among electricians, was entirely arbitrary.

Thank you all. That is very helpful. By the way, I had ABS and PVC transposed in my first post. It certainly makes sense to me that both should be permitted, and it seemed unduly restrictive to me that they would insist on one exclusively. The township in question is Northampton.

I cannot cite the code, but I have been told by a local plumber that PVC must be used for new work in this area (Bucks County, southeastern PA). I informally confirmed this with a different plumber at my place of employment. So I think it is likely correct. As for Tucson, I have observed that only ABS is used, but I don't know if this is code. Thanks for responding to my question.

I do live in Bucks County and my township does specify PVC for new work. My question is more general in nature. I was recently visiting a relative in the Tucson Arizona area, where they seem to use ABS exclusively. Just wondering why one material is chosen and the other is excluded. Why not accept both?

I'm not an inspector, just a Harry the Homeowner. I have been lurking for a year or more and have learned a lot from this forum.... thank you all! Maybe someone can clear up a curiosity of mine. The use of ABS versus PVC for DWV plumbing seems to be a regional thing. Depending where one lives, either ABS or PVC is required, but exclusively one or the other. From what I have read it seems that either is satisfactory from a functional standpoint. There are arguably some slight advantages to PVC. Does anyone care to speculate why the rules are written to allow one or the other but not both? Why does my township require that I use ABS and not PVC? I'm not talking about mixing ABS and PVC in the same house. Why do they restrict me to ABS when PVC would be equally functional? It seems that they are being unnecessarily restrictive.