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nsf-pw and nsf-dwv pvc

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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nsf-pw and nsf-dwv pvc

Unread postAuthor: Sean » Thu Jul 10, 2008 10:53 pm

I posted this in the combustion section but now realized this is for the construction materials, sorry for that.

I made a combustion spud gun about 6 months ago, before I found this site. I just now realized that it says nsf-pw AND nsf-dwv on the combustion chamber. It seems to be thicker than regular pvc pipe. Would it be considered to be pressure rated or not? thanks for all your help.

I'm supposed to go shoot this thing at my friends ranch tomorrow but need to know if it is safe or not :S
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Unread postAuthor: Killjoy » Thu Jul 10, 2008 11:09 pm

If it has nsf-pw on it then it is pressure rated. What's on the fittings though? Those tend to be more then likely dwv.

Seeing as it is a combustion though, it should be fine, dwv holds up just fine to the pressures created by a normal combustion.
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Unread postAuthor: iisthemuffin » Thu Jul 10, 2008 11:16 pm

Killjoy is right. A regular combustion does not have to sustain high pressures for an extended amount of time. It is exposed to what you call shock pressure. There is only force on the pipe and fittings for a brief moment. If it is able to withstand that then there is no problem.

Also, further elaborating what killjoy said, the fittings are what you should be most worried about. Well, i wouldnt say so much worried as i would cautious. Most non pressure rated fittings will suffice for a combustion. While not recommended in some cases, they will still work. If you have a cleanout cap on it, which i assume you do, just make sure there is nothing behind it when you fire. It is very common for a clean out to fail after so long and blow off.
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Unread postAuthor: Sean » Thu Jul 10, 2008 11:18 pm

Didn't know the difference back then between the different types of pvc, I made this for a school project. Sure enough, the fittings are dwv.. but they should be fine for a combustion?
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Unread postAuthor: iisthemuffin » Fri Jul 11, 2008 12:12 am

They should be, yes. Like i said, they are only exposed to shock pressure. Just make sure you have nothing behind the clean out cap when firing it.
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Unread postAuthor: Sean » Fri Jul 11, 2008 12:32 am

I usually put the end on the ground when i shoot and just shoot it up in the air. A friend of mine tried to shoot it like an rpg on one that he made and it blew off, it wasn't good
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Unread postAuthor: TurboSuper » Fri Jul 11, 2008 5:22 am

NSF-DWV in addition to NSF-PW just implies that it meeets the NSF specfifications for drain/waste/vent as well as pressurized water. Therefore, it is still considered pressure rated.

DWV fittings are, for the most part, fine for combustions. If you cement everything properly nothing should be blown off at all. My combustion uses DWV and I haven't had any issues so far.
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Unread postAuthor: jimmy101 » Fri Jul 11, 2008 12:30 pm

What kind of NSF-DWV fittings are they? There are two, take a look at the spud wiki page on identifying pvc parts (or see the images from the Wiki below).

If you have any of the evil "two-diameter" type fittings you might consider junking the cannon. If the fittings look like NSF-PW, that is they are a contant outside diamter, then you should be OK.

Most combustion spud guns have at least one non-pressure rated part since the cleanout plug is really a DWV only part (they don't put cleanouts in pressurized water systems).

Evil DWV parts look like (note the non-constant outer diameter for most of the parts) --
Image

Pressure rated parts look like --
Image
A few of these pressure rated parts have non-constant outer dimater but that is just because they are either reducers or spigot fittings. (Spigot means they have one end that is the same OD as a piece of pipe instead of having an ID the same as the OD of pipe.)
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Unread postAuthor: sirspuddest » Sat Jul 12, 2008 12:38 pm

I would ignore the DWV label given to a lot of pipe, if I were you.

If it's labeled as being Schedule 40, then it'll be just fine. Just look for some kind of pressure rating - if it's absent of a pressure rating, I wouldn't buy it.

In fact, most of the pipe I use is Charlotte brand NSF-DWV.
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Unread postAuthor: blind909 » Sat Jul 12, 2008 1:52 pm

sirspuddest wrote:I would ignore the DWV label given to a lot of pipe, if I were you.

If it's labeled as being Schedule 40, then it'll be just fine. Just look for some kind of pressure rating - if it's absent of a pressure rating, I wouldn't buy it.

In fact, most of the pipe I use is Charlotte brand NSF-DWV.


You are wrong. If it is labeld as being SCH 40 NSF-PW, THEN it is ok. PVC-DWV sometimes also has a pressure rating, like 2 inch Dwv sometimes says 240 psi @70 F, but it can still blow at as low as 1 psi, so when dealing with situations like this, you have to be VERY careful.
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Unread postAuthor: Mr.Sandman » Sat Jul 12, 2008 1:58 pm

when i did not know about the dangers of nsf dwv i made a marble gun that had a ball valve and i took it up to 100 psi fine although i STRONGLY don't recommend that you use it for pneumatics it is pretty strong. some people on here act like it is brittle as glass and that if you pump it up it will immediately blow up.
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Unread postAuthor: iisthemuffin » Sat Jul 12, 2008 2:24 pm

blind909 wrote:
sirspuddest wrote:I would ignore the DWV label given to a lot of pipe, if I were you.

If it's labeled as being Schedule 40, then it'll be just fine. Just look for some kind of pressure rating - if it's absent of a pressure rating, I wouldn't buy it.

In fact, most of the pipe I use is Charlotte brand NSF-DWV.


You are wrong. If it is labeld as being SCH 40 NSF-PW, THEN it is ok. PVC-DWV sometimes also has a pressure rating, like 2 inch Dwv sometimes says 240 psi @70 F, but it can still blow at as low as 1 psi, so when dealing with situations like this, you have to be VERY careful.


I believe you are wrong as well blind. He was wrong in saying SCH 40 makes it completely ok to use, but i would have to agree about the pressure rated part. If it is pressure rated to 240 psi that means it is pressure tested to that. Which means it should be completely safe at that pressure. If it blows at 1 psi it is obviously incorrectly manufactured.

DWV is not unsafe pipe to use as long as it is pressure rated. DWV is not a pressure related term. It simply means its made for drain waste. But a drain waste pipe that is pressure rated is just as safe as a SCH 40 pipe that is pressure rated.
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Unread postAuthor: blind909 » Sat Jul 12, 2008 2:29 pm

But if DWV sometimes is pressure rated, how come some people have still had it blow at low pressures?
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Unread postAuthor: iisthemuffin » Sat Jul 12, 2008 2:38 pm

Well, are you certain they were using pressure rated DWV?

I use to think that SCH 40 and DWV were terms of pressure rating as well. I learned they werent. SCH 40 is just the thickness of the pipe wall. DWV is just the desrciption of the use of the pipe. DWV usually is not pressure rated because its purpose is just to hold water. But ocassionaly they use DWV to hold pressurized water. Its still used for drain waste but it needs to hold some kind of pressure.

Im sorry if i keep rambling. I have troubles saying exactly what i need to sometimes.
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Unread postAuthor: Sean » Sat Jul 12, 2008 3:57 pm

Thank yall very much. I went out and launched it about 40-50 times and it was a blast. Thanks for yalls help :D
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