Wednesday, July 30, 2008

Safety Info on Four Inch PVC Pipe

I went down to the plumbing supply house today and rounded up some info on 4 inch PVC pipe that I believe folks ought to know.

What I learned is:

1. There are more types of PVC pipe than you may suspect.

2. I know of three schedules: Sched 20, Sched 40, and Sched 80.

3. Sched 20 has 1/8" sidewall on 4 inch pipe. Sched 40 has 1/4" sidewall. Sched 80 has to be ordered(at least at the business I went to) so the sidewall thickness couldn't be checked.

4. There are at least two types of core: foam core and solid core. The foam core is NOT able to withstand pressure. If you buy pipe and see bubbles inside the cut end it is not worth a hill of beans as a container.

5. Pipe that does not have a pressure rating is not suitable to withstand pressure. The pressure rating is found just after the SCHED rating.

6. The plumbing supply house "might" cut the length you want, but SCHED 40 solid core pressure rated PVC pipe only arrives in 20 foot lengths. That means you are looking at 45-50 Dollars in outlay for a container that is about 8-10 inches long. Yikes!

UPDATED: More Info on PVC pipe

7. Great link on PVC pipe pressure ratings: I note that the pressure rating on this site is noticably lower than the pressure rating of the pipe I bought. This is due to the figures being the industry standard. Individual pipe manufacturers are likely to exceed these numbers and will state so on thir product if they do. If not then go with the industry standard.

8. PVC pipe derates to 20 percent at 140F and long term failure occurs above that. Check the link at

I think this means PVC pipe should be abandoned and move to one of the other plastic pipe materials unless a non-heat environment can be achieved. According to the charts, PB and PEX perform the best in heat conditions, but have about 40 percent of the strength of PVC. CPVC performs marginally better with heat, but has the same strength properties as PVC.

Thanks to commenters for the additional data and links!


Anonymous said...

Informative info for those who are not sure but I've found a web sites:

The above web sites have charts with material specs-real handy.


Anonymous said...

There is an important factor about PVC that after the temp goes above the 140oF mark the pressue the PVC vessel will hold decrease with over temp specs.

Anonymous said...

That was a type-o error the temp should have read 140F on PVC piping.