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Piping questions

6K views 33 replies 10 participants last post by  Irelands child 
#1 ·
Has anyone had problems with either black pipe rusting or galvanized pipe flaking off & plugging something up? If so, how long did it take before you started having trouble? TP says galvanized will flake off while I have read other places not to use black pipe because it will rust. Given that copper is out of my price range & pvc is not an option, which will cause less problems? What I'm looking at doing for now is to run 4 pcs of 11/4" vertical in something like an 'M' connected by 90* fittings & short pieces at the top with T fittings & ball valve drains at the bottom. On the middle of the last leg put a T fitting, regulator, filter, & hose (someday a 1/2" hose reel) Will this take out enough water for blasting or painting or is a dryer still going to be needed when the time comes?

Thanks,
Steve
 
#2 ·
I seriously doubt you will have any problems with galvinized in your lifetime....
I just plumbed my shop for air this spring, using galvinized, and I don't see a problem with "flaking" as you say. Even if it did the heavy stuff would fall out at the drops...
Here is a link to some good guidelines to follow when doing your plumbing.
http://www.oldsmobility.com/air-compressor-piping.htm
Notice the chart about sizing. I think you will find 1 1/4 to be overkill (and expensive) I followed the quidelines as listed and am happy with my system...
Mark
 
#4 ·
I plumbed air systems as part of my business for over thirty years and have used galvanized, black iron and copper extensively. I have never seen the flaking problems that one hears about except for some minor problems when the system is first put into use and even this is not real common. The black iron works just fine also with rust not being much of a problem on properly run systems and the filter will take care of any rust particles that do find their way into into the air stream. Rust may be a problem if you do not have a filter however in that case you will have other contaminates also with some being worse than the rust. Until recently I would recommend copper for air lines but with the staggering cost of it today I think galvanized would be a more sensible choice.
 
#5 ·
oldred said:
I plumbed air systems as part of my business for over thirty years and have used galvanized, black iron and copper extensively. I have never seen the flaking problems that one hears about except for some minor problems when the system is first put into use and even this is not real common. The black iron works just fine also with rust not being much of a problem on properly run systems and the filter will take care of any rust particles that do find their way into into the air stream. Rust may be a problem if you do not have a filter however in that case you will have other contaminates also with some being worse than the rust. Until recently I would recommend copper for air lines but with the staggering cost of it today I think galvanized would be a more sensible choice.
I agree Guys, its the war stories that make you think twice but its only because the system was not install correctly, that when you run in to problems. depending on where you live. Would be a deciding factor for me which to use. Rust is from condensation so if you doing a big shop you could put in a dryer. But for most home shops and if you don't want to paint the black pipe then the Galvanized is the way to go.

Craig
 
#7 ·
crankshaftkid said:
Why wouldn't 3/4" sch 40 PVC work? It's rated at 480 psi.....
Rating has nothing to do with it. Part of the job of hard lines is cooling. Cooling the air supply before end usage creates much less condensation at the air tool or spray gun. Of course you should be running a filter/regulator right before the tool but less water is always better. Metal lines, whether steel or copper, will cool the air more efficiently then plastic will.
The other problem with the PVC is brittleness. PVC gets brittle over time and this is not a good thing with PSI's of 125 to 150. A brittle PVC pipe doesn't just burst, it sends little knifelike shards flying through the air...
Mark
 
#9 ·
PVC is not allowed, unless run inside steel conduit or buried underground, by OSHA or MSHA for any kind of compressed gas including air, this came about due to injuries resulting from ruptured air lines sending razor sharp shards flying like shrapnel. That high rating changes drastically with temperature plus impact damage that would cause only a minor leak or no leak at all to a metal line could cause a PVC line to rupture violently. This along with the fact that it contributes greatly to water in the lines due to it's poor cooling qualities makes PVC a looser just about any way you look at it.
 
#10 ·
Well guys, went ahead & got 40' of 1" black pipe along with a 8' long 1" hose to run from the compressor to the pipe. Now I have a project over the holiday weekend putting everything together. Will probably use pipe thread compound to seal the threads so it don't leak, have 2 24" pipe wrenches so getting it tight isn't a problem. Regulator-filter & tools from Eaton got here today so ready to get some use out of this thing :)

Thanks,
Steve
 
#12 ·
Crank, if it has worked so far that's fine and if you want to continue using it no one is telling you not to but the fact is if it is that old you have a REALLY dangerous set-up and it is nothing to joke about. Just because you have gotten away with it this long does not make it safe. Most systems using PVC will survive and the odds are yours will last also, for a while anyway, but don't kid yourself PVC is a VERY bad choice for air lines and if yours does let go you will see what we mean. You would be wise to scrap that stuff and redo it for real.
 
#13 ·
I totally agree with you and didn't intend for my post to be a joke but after re-reading it, it did kinda sound sarcastic. When I installed this stuff, I asked around a bit and got the "ya, it'll be ok" answer from a few people and it wasn't until years later that I started hearing that it wasn't that good of an idea. It wasn't until today that it was said exactly what it can do when it lets go and I don't like the sound of it. One thing I will do is turn down the psi it sees until I can get it out of my shop.
 
#14 ·
I replaced several PVC systems while I was still in business and I have seen some bulletins about line failures but actually the only major failure I saw first hand was caused by a guy shooting at a rat, but that is a whole 'nother story :rolleyes: While one can not fault a line for failure due to gun shots the results are the same regardless. If this had been a metal line there would have been a leak or at worst the line would have been completely severed but this PVC line simply disintegrated along several feet and the flying shards damaged two vehicles in the shop at the time but fortunately no one was hurt.
 
#15 ·
My system is well thought out and is supported very well. The clamps are tight enough to keep it in place but has enough 'give' to let it move to allow it to expand with temp changes. At least I think it's well thought out. Each of the 3 drops has drains below the outlets and are placed in areas where they cannot be hit unless you go out of the way to get them. Rats are not a problem around here but I have 'other' ways to take care of them if they ever did show up but I have used my shop as a 'firing range' a few times lol. Sure would be nice to be able to find some stainless steel tubing and fittings! Anyways, I will be pulling out all the PVC very soon....about 200 feet of it. And btw, thanks for the heads up about the real dangers of what happens when it does let go.
 
#17 ·
My previous underground PVC water line gave us no problems for 28 years. Then 3 major leaks in one month. We re-plumbed the system with new PVC. One of the oddest things was when we tossed a 10' length of old pipe from the trench on the ground a few feet away from us - it broke into 3 pieces like it was glass. Seems that it just reached a point in its life where the material in the pipe lost the ability to continue to bond with itself. I'm sure we could have thrown a new piece of pipe as far as we could have with no damage. Anyway, it does seem that one day soon your air supply could explosively come apart.
 
#18 ·
Lust, That is a VERY good example of what some of us have been trying to get across for some time now but some people will still argue that PVC is just fine and will continue to use it. I have been of the opinion that in the near future as some of these systems are getting older and the PVC is breaking down due to various factors there will be an increase in the number of accidents. There will inevitably be some serious injuries from this and I think that PVC will eventually see little use as a carrier for compressed air as people learn, some the hard way. This will unfortunately happen too late for many.
 
#20 ·
Crank, You will probably notice a very welcome side benefit of collecting more water in you drains and separator :) This will come about due to the much better cooling of the air from the metal lines allowing the water vapor to condense and be collected in the system instead of ending up in your air tools or worse, if you do any painting, in your paint! The poor cooling quality alone of the PVC is more than enough reason not to use it. Switching to metal line is a really good idea and I think you will be glad you did.
 
#21 ·
Got everything put together yesterday works like a dream. Had the 3" cutoff tool running constant for 5 min & compressor never dropped below 110 psi, & could still rest my hand on the pump :) Will shoot it with the IR & get an actual temp reading today. So far looks like it will keep up with a 3" cutoff, & 6" da sander running full bore so looks like I'm good to go :D 1" hose from compressor to pipe got warm along with about 4' of the first section of pipe but after that everything was room temp. Had the auto drain on the compressor set to blow off for 2 sec every 10 min & when the drains on the bottom of the pipes were opened no water came out. Having never had a compressor or air tools before I like this a lot. Used pipe thread compound & had no leaks even with a mix of american & chinese pipe and chinese & thailand pipe fittings. About the only thing left to add for now is another outlet for straight line pressure for filling tires, airtank, ect. This is so much better than running a hose off the compressor like I had before, not going to miss the water.
 
#23 ·
21 year old PVC will be rather brittle, especially if it's been exposed to sunlight a lot. If it's a UV resistant PVC that's even better. Is the PVC exposed or in the walls? If in walls it's probably safe. If exposed, you could cover it with a 3/4" plywood shield and some standoffs. That way if something does give the force will be directed up and down, not across the shop and into you. Just because it's worked fine so far doesn't mean it won't fail at some point. If it does it will likely be a catastrophic failure. Hopefully no one will be in the shop if/when it happens.
 
#24 ·
Farna, I think he has decided to replace it which is by far the best choice however you have a GOOD point there and that is that a PVC system should be shielded in some manner. I realize that replacing a system that is already installed and operating can be a major PITA not to mention a big expense. For someone who is using PVC I would strongly recommend replacement but for those who are unwilling to do so for whatever reasons they may have then adding a shield of some sort would not be expensive and in most cases not be a lot of work. It need only be a simple one sided (assuming one side is against a wall) structure and in fact should not be boxed in completely since you would be redirecting the expanding air flow and not trying to contain it. This simple and inexpensive mod just might save someone from a very serious injury or worse! I cannot stress strongly enough that replacement is the best way to go and if everyone could see those safety bulletins (I have been trying to locate some) or see the one incident I did examine they would probably want a concrete wall between them and that stuff!
 
#25 ·
The failed PVC that I mentioned in my above post was buried two feet underground for its entire life. It was shiny new when installed and the deterioration was totally without exposure to UV rays. We uncovered the pipe in the trench and tossed it out of the trench to replace it.
 
#26 ·
No PVC - never for compressed air

This is an old subject but needed to add my .79 cents worth.

I put temporary PVC air piping in my garage, just to paint my car, but, after reading this post and a couple of others, decided the risk plus the amount of water carryover required me to change to copper. While pulling the PVC down, I wasn't particularly careful - going to the dump - so just kind of yanked it around. EVERY JOINT but one fractured at the fitting. Just for the heck of it, I took my tubing cutter and cut about 1/2 way thru near that one fitting that was still whole, gave it a yank, and "lo and behold", the pipe fractured at the fitting and the place that I partially cut bent but stayed whole. My guess is that the glue has a molecular effect on the base material, and weakens it to the point that a good shock or pressure will 'kill' it.

Before anyone asks, the pipe was made by Charlotte Pipe on May 1, 2006, and I purchased it from Home Depot and installed it over the July 4, 2006 weekend.

I have installed about 40 feet of copper - 1/2", and now feel fairly safe. It still has some water carry over, but I will put a precooler after the compressor and make up a good trap system at the far end, possibly using a Sharpe.

I am aware that my compressor is probably smaller than it should be at 6.5 peak Hp and 10.5 SCFM@90psig/13.5 @ 40 psig. The tank is a 30 gallon but runs too much(50% duty cycle), tho will keep up with all my air tools. I do run it with a fan blowing on the compr. and put Castrol Syntec in it to try to keep the friction losses down - regardless of whatIR said.

I hadn't intended on painting my own car until I started getting $10-15K quotes on a roadster so I'm stuck with a compromise piece of equipment and a early retirees fixed income.


Dave
 
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