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Re: [TowerTalk] tubing vs. pipe-- and a question

To: "Richard (Rick) Karlquist" <>,"Jim Jarvis" <>, <>,<>
Subject: Re: [TowerTalk] tubing vs. pipe-- and a question
From: Jim Lux <>
Date: Sat, 02 Jun 2007 06:01:39 -0700
List-post: <>
At 10:15 PM 6/1/2007, Richard \(Rick\) Karlquist wrote:
> > Except for plumbing.. 1" PVC Sch 40 pipe has no dimension that's
> > 1".  It does have an od that's the same as some iron or lead pipe
> > that DOES have a 1" id.
>"One inch" pipe does NOT have an ID of 1".  It's actually about 1.05"
>for schedule 40, less than 1" for schedule 80.
>You are correct that both PVC and iron pipe have the same OD, which
>is 1.33 inches for "One inch" pipe.
>Many years ago (like 150) "one inch" pipe actually had an ID of
>one inch and an OD of 1.33 inches, hence a wall of .165 inches.

That's sort of what I figured.  When I said "some iron or lead pipe" 
I was thinking of ancient times not modern.

>When schedule 40, 80, etc, was introduced, they standardized on
>the 1.33 inch OD so the threads would be the same.  The ID then
>became a function of the wall thickness.  The thickness that are
>called out happen to result in the ID being different than the pipe size
>except 4 inch schedule 40 which happens to coincidentally have
>an ID of 3.999 which you can call 4 inches if you like.  I think
>the thicknesses in the schedule were chosen for a certain water pressure.

Yes, and there's probably some weird connection between the actual 
number 40 or 80 and some aspect of the pipe manufacturing (like sheet 
metal gauges) Probably something like you can make a rod length of 
pipe with a sheet 40 barleycorns thick or something like that.

>Rick N6RK


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