Pipe Sizes - now and then
Greetings Snelson,
I’m curious about your 3.5†pipe. A common mistake with pipe is trying to measure it with a tape measure. If your clean-out plug measures 3.5â€, then what you have is a 3 inch pipe.
It’s kinda like trying to find 2 inches or 4 inches on a 2 x 4 stud. A long time ago (in a land far – far a way…) when steel chemistry was crappy, the pipe walls were thicker. So, an I 1/2 pipe I.D. was 1.5â€.
As steels improved, they were able to make the wall thinner, but to keep the pipe “backwards compatible†with existing fittings, the pipe O.D. was kept the same as before.
Pipe
Size:
1/2" =0.840" o.d.
3/4" =1.050" o.d.
1" =1.315" o.d.
1 1/4" =1.660" o.d.
1 1/2" =1.900" o.d.
2" =2.375" o.d.
2 1/2†=2.875" o.d.
3" =3.500" o.d.
4" =4.500" o.d
5" =5.563" o.d.
6" =6.625" o.d.
8" =8.625" o.d.
10" =10.750" o.d.
12 =12.750" o.d
Phat