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DWV PW Fittings

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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DWV PW Fittings

Unread postAuthor: mattyzip77 » Mon Jul 18, 2011 9:51 pm

Numerous plumbers and different people that work at Lowes and Home Depot say that there is really no difference between DWV and PW fittings. I get the same answer, as long as its schedule 40 its pressure rated. I know it says different here at Spudfiles, but is there really a difference??????
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Unread postAuthor: Mr.Tallahassee » Mon Jul 18, 2011 10:02 pm

The people at Lowes and Home Depot do not know anything. They aren't the people who made the pipe. DWV is typically not pressure rated and the fittings are shallower and don't have as much area to be glued. It may be schedule 40 but schedule is NOT a pressure rating. There is a LARGE difference. ALWAYS check for a pressure rating on the pipe. Pressure rated fittings have deeper sockets than DWV fittings. Also, do NOT use cellular core for ANY pressure. It is technically schedule 40 but the thickness of the actual pvc is half of true schedule 40 and the other half of the thickness is basically foam.
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Unread postAuthor: mattyzip77 » Mon Jul 18, 2011 10:23 pm

I know what the difference is physically and on paper, is it that huge of a difference though?? Yea, its a tad thicker, and a tad deeper. I use the good fittings as long as the store has them. but my one pneumatic cannon has a 3 x 1 1/2 bell reducer on it thats not pw, but its thicker than any other part on my cannon and in my opinion looks the safest. I know that the guys at home depot dont know dik, but its hard to question a master plumber thats been doing his trade for over 40 years!!
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Unread postAuthor: Gaderelguitarist » Mon Jul 18, 2011 10:35 pm

Master plumbers use the pipe for different reasons than your average spudder. It's already technically unsafe to use PVC at all for air pressure systems, so to lower your safety standards by using DWV parts is just asking for trouble.
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Unread postAuthor: mattyzip77 » Mon Jul 18, 2011 10:45 pm

ya, he knew what I was using the pvc for. he even gave me a bunch of fittings, and he said as long as I didnt go over 150 psi and the pipe and fittings were not defective, than I would not have anything to worry about!!
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Unread postAuthor: Technician1002 » Tue Jul 19, 2011 2:45 am

Shallow sockets on fittings like in the video below shows the problem with using DWV fittings on a pressure system.
[youtube]http://www.youtube.com/watch?v=cJ0KnAVbxMQ[/youtube]
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Unread postAuthor: jimmy101 » Tue Jul 19, 2011 4:30 pm

Mr.Tallahassee wrote:The people at Lowes and Home Depot do not know anything. They aren't the people who made the pipe. DWV is typically not pressure rated and the fittings are shallower and don't have as much area to be glued. It may be schedule 40 but schedule is NOT a pressure rating. There is a LARGE difference. ALWAYS check for a pressure rating on the pipe. Pressure rated fittings have deeper sockets than DWV fittings. Also, do NOT use cellular core for ANY pressure. It is technically schedule 40 but the thickness of the actual pvc is half of true schedule 40 and the other half of the thickness is basically foam.

Mostly true except for the thickness part.

Sch40 cell core generally has about the same wall thickness (in pipe) as solid core. Both are 100% Sch40 since Sch40 only respecifies dimensions and not pressure rating.

BTW, cell core is fine for 1X combustion guns.
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Unread postAuthor: Mr.Tallahassee » Tue Jul 19, 2011 4:42 pm

Cellular core pvc has the same overall wall thickness but only 50% of that wall thickness is actually pvc. the other 50% is the core. And as to using it for combustion guns, this is a pneumatic cannon thread so that really doesn't apply here but yes, it is fine for 1x combustion guns.
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Unread postAuthor: Fnord » Tue Jul 19, 2011 6:21 pm

I don't see why anyone would want to use cell-core pvc in a 1x combustion when actual pressure rated pipe is only a marginal amount more expensive. If a round jams in the barrel of a cell-core gun you suddenly don't have much of a safety factor, especially if you drilled into the chamber.
Cell core ABS is excluded of course, due to its impact resistance.


Oh yeah, and to repeat what everyone else has already said- Sch40 is only a wall thickness. Sech80 can be treated as a pressure rating however, since I don't believe standard pipe is made to those dimensions with DEV applications in mind.

Also, in some cases you DO NOT want to listen to the guy with 40 years experience. Remember such people grew up without an ever-present source of information like we have today, so they may be more prone to preaching myth and legend. And if they're wrong you can't actually convince them, since you're a stupid kid and they've been doing this for 40 years.
I see it all the time at work but don't even bother to say anything anymore... but I do sit back and smile when something goes wrong I could have predicted.
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Unread postAuthor: Technician1002 » Tue Jul 19, 2011 7:18 pm

When using the wisdom of older folks, look for the ones who constantly study to keep their skills current. If I stopped learning when I got my certification, I would never touch a computer. I graduated HS in 1975. IBM released the PC-XT in 1981.

I've seen the old timers lost in the 1960's. I've also worked with engineers designing the cutting edge with the latest tools and mixing in the solid basics.
One is obsolete. the other is worth hanging with.

A welder that only knows stick and gas welding is obsolete. A welder that includes TIG, MIG, Plasma cutters, Induction brazing, certified pressure vessel welding etc is very valuable. Keep your skill set current.
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