SpudFiles

Alright so I went to Menards to get some ideas about something I want to build but I noticed the had no schedule 40 in 4" fittings, just DWV; and I was always told that DWV was awful and unsafe to use in pneumatics. So I went up to the plumbing section's customer service center and asked if they had any 4" fittings that were pressure rated/schedule 40, and he said they were the same thing. I kept thinking "well that just couldn't be..." and asked the man "if that is so, then why do you have two versions of every smaller fitting? (There were duplicate fittings for most sch40 fittings)" and he said unblinkingly that they were still the same thing. I was losing my mind over it so I asked "will the 4" DWV fitting be able to handle pressures of 100+ PSI?" Once again I received a yes along with "other people building spud guns have used them and said they worked just fine."
Is this all true?? I've always been warned against using these fittings...

Don't do it!!! No they're not the same. You will need to find a contractors plumbing suppy. There should be one in your area. You won't find anything pressure rated over 2" in most home improvement stores.

Yes you've probably seen it done, but they were idiots, don't be one yourself.

~NooooooB~ wrote:So I went up to the plumbing section's customer service center and asked if they had any 4" fittings that were pressure rated/schedule 40, and he said they were the same thing.

Well, they're not mutually exclusive (or inclusive).

Pipe and fittings can sometimes be found marked with both a pressure rating and a DWV mark, as pressure pipe is certainly capable of (if overkill for) drainage and waste, and SCH 40 pipe is often not pressure rated (it's a sizing standard, and doesn't stipulate material strength/quality).

However, if it's fittings with that spartan look of shallow sockets and thin walls, it's definitely not safe for pressure.

I tested this and found PVC is brittle and the shallow sockets for DWV tend to crack loose, break, or fail in interesting ways, even after passing initial testing. My Mouse Musket was a study of the impact resistance of PVC. If it takes a beating, it will break.

I looked at the soda pop bottles and their pressure handling and thickness then looked at Sched 40 ABS drain pipe and wondered if it was tougher than a simple thin pop bottle. This turned out to be the case. See my ABS test cannon for the results of this long running experiment.

Summary, don't use DWV PVC Pipe for pressure. ABS is tough stuff. Takes a beating.