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Need to know the difference

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Need to know the difference

Unread postAuthor: atreverse12 » Thu Mar 29, 2007 12:03 pm

Ok, I saw a 2005 post that alluded to this question (so i'm really not trying to be a post whore) , but I'm still not sure o.O ... I already looked on NSF.org, and they said that the difference between NSF-PW and NSF-DWV piping is that "-pw" means that you can hold potable drinking water in it, and that "-dwv" means that you can't. So, I posted a question or two yesterday and got some great responses that my bell reducers were NSF-DWV and that they were not safe. My question is: What is the actual difference? also, what should I use instead of a bell reducer? (I couldn't find any bushings large enough) I plan on going by a plumbing supply store...would they have properly pressure rated bell reducers there? I will attach a picture (the second one) of my parts leading from my pressure tank to my valve. (and another one of my paint job i'm so proud of.) Please give this cannon builder some much needed advice :) .

p.s. If there is any alternative to a bell reducer, i'm all ears.
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Attachments
Labeled unglued.jpg
Bell reducer and pressure tank
Put Together unglued.jpg
My uber-cool paint job =)

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Unread postAuthor: keep_it_real » Thu Mar 29, 2007 12:08 pm

I just went to nsf.org and this is what it said...

"Products that meet all applicable performance standards for pressure-rated potable water applications"

"pressure-rated" is the key there

DWV stands for - Destruction With Violence.

Some people do use it but it's just not quite as safe.

nice cannon. I think you should mod the sprinkler valve and then strap the chamber and barrel together so it's not all wobbly. Your probably not done yet though so never mind. Next time I would put the sprinkler valve on top so there is less dead space.
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Unread postAuthor: rna_duelers » Thu Mar 29, 2007 4:51 pm

As for the Bell reducer there is a saftey issue wiht the socket depth,it isnt nearly as deep as a coupler and reducer socket depth that is were the weakness is.

But nice lil cannon might sugest a whole camo paint job and modded valve :wink: .

Your best bet would be going to a plumbing store,they would have most parts and if need they would certainly be able to order them in.
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Unread postAuthor: DK » Thu Mar 29, 2007 8:45 pm

keep_it_real wrote:I just went to nsf.org and this is what it said...

"Products that meet all applicable performance standards for pressure-rated potable water applications"

"pressure-rated" is the key there

DWV stands for - Destruction With Violence.

Some people do use it but it's just not quite as safe.


You have the right idea, but not quite there. DWV stands for "Drain, Waste, Vent". The designation means the pipe is designed to be used in gravity-fed systems. This means that the pipe is rated for a maximum pressure of about 10psi. It does not mean that it fails catastrophically, as indicated by your post.

atreverse12:

You're correct about the "-pw" rating on pressure rated pipe. The pipe you have, the "-DWV" pipe is not designed for any amount of pressure higher that what gravity produces on liquid in a drain application. Bell reducers, because of their shape are typically not pressure rated (although pressure rated bell reducers can be special ordered from some companies). As a rule, expect your local hardware store to carry pressure rated PVC components up to 2" in size but beyond that, DWV components are the norm. However, a plumbing store (for example, the one you're going to) will likely carry pressure rated PVC as large as 4" in diameter.

Regarding non-pressure rated components, these are typically thinner than pressure-rated pipe and fittings and hence are cheaper to manufacture. This means they cost less to buy, but you get what you pay for, right? When purchasing PVC, look for the rating NSF-PW. It is usually followed by a pressure rating such as 200psi (for 4" pipe) or something similar. Beware of pipe without a pressure rating, as this would automatically make it DWV, regardless of how thick it is. Socket depth (how far you can push the pipe into a fitting) is less than in pressure rated fittings as well.

I would suggest using a bushing as an alternative to your bell reducer, as they are pressure rated. Don't worry about not being able to find one PVC manufacturers make them in a variety of sizes for pressure applications.

The plumbing store is your best bet to find out more information on the kinds of pipe available. Like rna_duelers said, if they don't have what you need, they can certainly order it in.

Cheers.
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Unread postAuthor: ArticWolf » Fri Mar 30, 2007 3:40 am

I have another question that pertains to this. Mainlly what is the differance between sch-40 with printing on it and sch-40 without printing on it. I was told from the plumbing store I got it from that it was NSF-PW and that it was pressure rated at 480 psi or something like that and it was just were it was cut off. (it is 4" sch-40, may be NSF-PW) Was just wondering are NSF-DWV coupling's safe to use?
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Unread postAuthor: integral » Fri Mar 30, 2007 4:21 am

ur best bet is to use fittings that are "actually" pressure rated. if not sure, then just ask the sales guy to give u the stats. if he/she cant, dont buy it. personally i have no experience but i have read many posts from credible members saying that dwv pipe isnt as dangerous as everyone makes it out to be, providing u dont go over a certain pressure, ie 60psi. so that dwv coupling "might" be ok, but for an extra couple of bucks (if that) get one that is designed to handle the pressure. better safe than blind.
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Unread postAuthor: DK » Fri Mar 30, 2007 5:18 am

ArticWolf wrote:I have another question that pertains to this. Mainlly what is the differance between sch-40 with printing on it and sch-40 without printing on it. I was told from the plumbing store I got it from that it was NSF-PW and that it was pressure rated at 480 psi or something like that and it was just were it was cut off. (it is 4" sch-40, may be NSF-PW) Was just wondering are NSF-DWV coupling's safe to use?


If they're from the same pipe, there's no difference at all ;) However, i'm not entirely clear on what you mean by "sch-40 with printing on it and sch-40 without printing on it". Do you mean that the section of pipe you have has no printed information on it and was cut from larger stock that did?

NSF-DWV couplings are not pressure rated (hence the "DWV" rating) and generally can be safely used in a combustion cannon, but are not recommended. Anything else, such as a pneumatic, would require a pressure rated component.

Keep in mind that the schedule rating (ie. SCH-40) refers only to the size standard of the pipe and fittings, not the pressure rating.

ArcticWolf, as an aside, are you by any chance an artist?

Cheers.
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Unread postAuthor: ArticWolf » Fri Mar 30, 2007 1:15 pm

Dk Wrote:

However, i'm not entirely clear on what you mean by "sch-40 with printing on it and sch-40 without printing on it". Do you mean that the section of pipe you have has no printed information on it and was cut from larger stock that did?

Yea, That Is what I ment. Sorry it was a late night.
DK Wrote:

ArcticWolf, as an aside, are you by any chance an artist?


Yea, I am an artist this picture was on my con badge I used at Anthrocon In Pittsburg PA in 2006. It is an Anthromorphic convention with artist's and costumer's. (IE: Mascot's and the like animals)
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Last edited by ArticWolf on Sat Mar 31, 2007 1:34 am, edited 1 time in total.
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Unread postAuthor: atreverse12 » Fri Mar 30, 2007 1:23 pm

Thanks for all the tips! I did some research and found a wholesaler near me, and they showed me all the differences and such. As for a bell reducer, they're unsafe unless you get them in schedule 80, which are like 25 bucks each :shock: so I just went with a 4" schedule 40 bushing that takes a 2" bushing and then connected that to the other stuff pictured. The 4" bushing is connected to my 4" pressure tank with a coupler. I just finished staining my shoes purple / cementing the parts together, and i'll be sure to post a pic in the showcase when it's all painted.
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Unread postAuthor: DK » Sun Apr 01, 2007 5:04 pm

ArticWolf wrote:Yea, That Is what I ment. Sorry it was a late night.


Heh, no worries.

Yea, I am an artist this picture was on my con badge I used at Anthrocon In Pittsburg PA in 2006. It is an Anthromorphic convention with artist's and costumer's. (IE: Mascot's and the like animals)


The reason I asked, is because I am as well. A newbie to the trade but what the hell.
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Unread postAuthor: ArticWolf » Mon Apr 02, 2007 6:15 am

I have been drawing for a while. I started tracing first but after that it got easyer. Heck I drew the way I wanted my cannon to look like, it may be a standerd inline but what the heck it was fun to draw. I got to keep it secret for now till the contest. I have not put it together yet still waiting for my ignition system. I'll get it finished a put it up in the contest show case or what ever it is called soon I hope. lol
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