[oldred]

Black iron pipe is steel however the fittings are usually cast iron these days and of poor quality, I saw one 1/2" coupling that was so chocked down inside it would flow less than a 1/4" fitting. These fittings are safe to use as long as they are not welded (rarely done anyway) but they may be very hard to seal and can even be porous. Good quality fittings are getting harder to find and even though they too are cast they are cast steel not cast iron (straight fittings are made from steel pipe not cast), cast steel fittings are usually stronger than the pipe, have clean cut easy to seal threads and can be welded if needed. Go to a real plumbing supply not a McHome store for fittings and insist on quality fittings, stay away from any fitting that says CHINA on it!

[MARTINSR]

Originally Posted by oldred

stay away from any fitting that says CHINA on it!

Then we will never buy anything.

Brian

[oldred]

Originally Posted by MARTINSR

Then we will never buy anything.

Brian

Disgusting isn't it? It would seem EVERYTHING and the stinkin box it comes in is made in China these days!

[stich626]

Originally Posted by oldred

Disgusting isn't it? It would seem EVERYTHING and the stinkin box it comes in is made in China these days!

thank the EPA won't you

[Old Fool]

Class 125 fittings are made from cast iron
Class 150 black or galv fittings are made from mallable iron
Class 300 (ARR) black or galv fittings are made from mallable iron
There are high pressure fittings, say 3000psi that are made from forged steel.

2 years ago my plumbers came across two 1/2" black caps that wouldnt hold a pressure test. Both of them were weeping very slightly right in the country of origin emboss on the end of the cap. I saved the 2 caps, I was hoping for them to come across a 3rd but so far it hasnt happend.
The 2 caps I have , one leaks in the U, the other leaks in the S. Sure would have liked to complete the set.

[Old Fool]

Originally Posted by oldred

Black iron pipe is steel however the fittings are usually cast iron these days and of poor quality, I saw one 1/2" coupling that was so chocked down inside it would flow less than a 1/4" fitting. These fittings are safe to use as long as they are not welded (rarely done anyway) but they may be very hard to seal and can even be porous. Good quality fittings are getting harder to find and even though they too are cast they are cast steel not cast iron (straight fittings are made from steel pipe not cast), cast steel fittings are usually stronger than the pipe, have clean cut easy to seal threads and can be welded if needed. Go to a real plumbing supply not a McHome store for fittings and insist on quality fittings, stay away from any fitting that says CHINA on it!

Stay away from the 7 sided Russian pipe too, even China pipe is rounder than it is.

[406 bug]

Originally Posted by MARTINSR

Yes and you want galvanized not black. Black is for gas not water, unfortunately compressed air is full of water so it shouldn't be used.

Brian

Galvanized is not commonly recommended for air delivery. Black iron (steel) is preferred over galvanized due to the fact that when the moisture breaks down the galvanized it tends to peel off and provides greater opportunity for contamination/ obstruction. However, Stainless, copper, and aluminum are better choices.

[MARTINSR]

I have heard people saying that but never a paint gun manufacturer. Black pipe has no coating at all and rusts.

Brian

[406 bug]

Originally Posted by MARTINSR

I have heard people saying that but never a paint gun manufacturer. Black pipe has no coating at all and rusts.

Brian

I agree Brian, I would use copper to eliminate any rust problems.

[oldred]

I have seen many galvanized air systems in the years I worked with them and I never once saw a problem with the galvanized plating flaking off, I suppose it's true but an air system normally has so much junk in it that it must be filtered anyway so any small amount of flaking would be insignificant. Also black iron is commonly said to be a bad choice, about as often as galvanized, because it is supposed to rust inside but again the air must be filtered anyway so it just don't seem to be a problem, besides the pipes I have seen (both galvanized and black) are usually coated with an oily residue inside after being used for a while and rust does not seem to be a problem with either. The fact is while both types of pipe get bad raps from differing opinions either works just fine, some of the systems I have repaired/replaced were many years old and the only time I have ever seen rust to a problem is if a system has been left unused for years. I would think in the case of piping being left unused for a long time (years) galvanized would probably have an advantage but honestly either works just fine.



Personally unless cost is prohibitive my choice is Copper, especially when short runs of piping are used from the compressor to the hose outlet.

[Old Fool]

Originally Posted by oldred

I have seen many galvanized air systems in the years I worked with them and I never once saw a problem with the galvanized plating flaking off, I suppose it's true but an air system normally has so much junk in it that it must be filtered anyway so any small amount of flaking would be insignificant. Also black iron is commonly said to be a bad choice, about as often as galvanized, because it is supposed to rust inside but again the air must be filtered anyway so it just don't seem to be a problem, besides the pipes I have seen (both galvanized and black) are usually coated with an oily residue inside after being used for a while and rust does not seem to be a problem with either. The fact is while both types of pipe get bad raps from differing opinions either works just fine, some of the systems I have repaired/replaced were many years old and the only time I have ever seen rust to a problem is if a system has been left unused for years. I would think in the case of piping being left unused for a long time (years) galvanized would probably have an advantage but honestly either works just fine.




Personally unless cost is prohibitive my choice is Copper, especially when short runs of piping are used from the compressor to the hose outlet.

Agree with the black pipe is fine.

I have worked on the air system in an old defense plant built at the beginning of WW2. ( We added air dryers)
The plant air system is all black pipe, and after all those years it is still in service and not having any maintenence issues.

Type L copper is also my choice if $$ aren't an issue

[MARTINSR]

Originally Posted by oldred

I have seen many galvanized air systems in the years I worked with them and I never once saw a problem with the galvanized plating flaking off, I suppose it's true but an air system normally has so much junk in it that it must be filtered anyway so any small amount of flaking would be insignificant. Also black iron is commonly said to be a bad choice, about as often as galvanized, because it is supposed to rust inside but again the air must be filtered anyway so it just don't seem to be a problem, besides the pipes I have seen (both galvanized and black) are usually coated with an oily residue inside after being used for a while and rust does not seem to be a problem with either. The fact is while both types of pipe get bad raps from differing opinions either works just fine, some of the systems I have repaired/replaced were many years old and the only time I have ever seen rust to a problem is if a system has been left unused for years. I would think in the case of piping being left unused for a long time (years) galvanized would probably have an advantage but honestly either works just fine.



Personally unless cost is prohibitive my choice is Copper, especially when short runs of piping are used from the compressor to the hose outlet.

All good points.

Brian

[gow589]

By the time you start adding up you can get fairly close to price to a fairly nice air system. I set up a system with the Rapidair using the 3/4" duratec line good to 200psi. It was easy to set up and does away with most metal pipe issues. Byt he time you add up pipe and fittings it's worth comparing how close you came to a system like this:

http://www.rapidairproducts.com/index.asp

[speede5]

That Duratech stuff looks just like the pex I used for my infloor heat lines. I was thinking pex would be great for an air system. Sounds like I might rethink that. Copper would be my next choice but it is getting really expensive.

Are you anti PVC guys anti pex too? I really can't see pex having the same issues as PVC. On second thought, pex is sensetive to sunlight, so probably not the best choice. I wonder how the Duratech handles sunlight.

[oldred]

Any kind of plastic will be a bad choice because of moisture even if it does not have safety issues. Heat dissipation to condense the water vapor contained in the hot air from the compressor is a big factor for a piping system in both design and material and in that respect plastic would be a poor choice. In terms of safety PVC is a known hazard and many injuries have resulted from it's use, so many accidents have happened that it has been banned for use for pressurized gases (including air) by both OSHA and IMSHA. PVC is relatively brittle and gets even more so with age, exposure to sunlight and oils in compressed air so it's dangerous when first installed and gets worse with age. Other types of plastics used for pipe may not be as brittle and in fact I don't know of any that would tend to disintegrate into shrapnel like PVC but I might be wrong about that, maybe someone here with some plumbing experience could weigh in on that one. In any case I think plastic would be a bad choice just because of the moisture issue but if that's not a problem for the user and the pipe does not have the disintegration hazard of PVC then there may be some types of plastic that are safe to use.