5 replies to this topic

[thesoxfan1234]

Hey everyone, to start I am a fairly new member and this question most likely have been asked, but why is 1/2 pvc called "1/2"? It has no relation to the diameter of 1/2. I am just curious to know why.

[SlightlySane813]

I've noticed the same thing.

The only relation that I've seen is that 1/2 inch cpvc fits very snugly inside of it.

[BrokenSVT]

I had the same question some time ago, and a little Google searching quickly supplied the answer.

The short version is that back in the day, the folks who supplied the standards for pipe sizing used a different system. Back then, wall thickness was standardized which supplied a consistent OD and ID-- then came different scedules(IE sch40, sch 80 etc). Because the OD determined the fittings used, that dimension was the more important to remain unchanged; while the ID had previously been used to "name" the pipe.

And they all lived happily ever after.

[phillypretzel]

And to add further confusion PVC is made to the IPS (iron pipe standard) while CPVC is made to the CTS (copper tube standard). This explains why 1/2" PVC and 1/2" CPVC have such different OD's and cannot share fittings. I seem to remember Slug posting a thread explaining all this awhile ago.

[ghost recon]

thats also why the 1/2 couplers dont fit them you have to buy a bigger coupler

[Draconis]

This article explains it all pretty well. Basically, it's all holdover from when the plumbers tried to keep the sizing confusing, so that you had to be trained on what meant what. http://en.wikipedia....nveyance)#Sizes

Edited by Draconis, 01 January 2011 - 03:11 AM.