copper or black iron pipe

[kc-steve]

3-5 psi an hour loss seems to be out of the norm for most systems. Especially if it is a simple home air system.
Every time you need air you have to wait for it to pressure up and alot of unneeded wear on your motor. I have also seen some systems start to leak from a system that is pressurized and depressureized constistantly which tends to work the connections.
You could try and put a little pipe dope on your union connections to help it seal better.

Thanks for the advice. But the primary concern for the compressor is that it doesn't run too often. Pressure up time is only around 10 minutes or so. When painting I am using far more air (~6 cfm) than the 3 to 5 psi PER HOUR leakage. And like I said, I shut it down completely when I am not using it, which might be once a month maybe. Even if I leave the compressor at full pressure with the steel piping closed to the tank I still get 1 or 2 psi per hour leakage inside the compressor. In other words, if I leave it fully pressurized, disconnected from the steel pipe and unused it will still cycle once every 24 hours. It has been that way since it was new. But I'll keep that in mind and watch for a greater leakage in the future.

While in use, the compressor operates when it reaches ~100psi and shuts off when it reaches 135psi. Meanwhile my output regulators are typically set to 50psi at the compressor, 40psi at the end of the steel pipe, and 30 psi at the gun. I currently have no problems using it. But thanks anyway.

Steve

 

[bdog]

3-5 psi per hour is a lot of leakage. My system has over 200' of copper pipe. It was the first time I had ever worked with copper. I had it pressured up to 150 psi and shut off my compressor as I was going out of town for 3 weeks. When I came back I looked and it was between 145 and 150 psi after sitting for 3 weeks.

 

[Torque1st]

I'm not sure, but I think the "galvanized" is only on the outside, like black pipe is only black on the outside.

FYI- Galvanized pipe is coated inside and out.

 

[MrMark]

Dope is a no-no on unions. The unions rely on pure metal to metal contact, just like flare. The dope will not help and will only cause problems. I have seen some put dope on the threads of a union to help with the tightening process. Other than create an unnecessary mess, this does no harm. A drop of oil would work too.

Another tip on black steel: the dope only goes on the root of the male threads and you don't need a lot. The thread can only take a minute amount and the rest just gets pushed up the fitting and creates a mess.

I have seen some gunked up pipe where the plumber put the dope on both the female and male threads. In this case the excess dope gets pushed inside the pipe too.

You really have to pay attention to the fittings with the black pipe. Many fittings I have tried are not threaded correctly and allow the pipe to turn in way too far. If you see the pipe threading in past 4 turns you can almost guarantee you will have a problem. The tapers have to meet at the same point for the system to work.

 

[bill9860]

I have read other threads and and even read elsewhere that galvanized pipe can flake inside. Yet I have friend who has used nothing else for over 40 years with no issues. Current system in use is 25 years old and he does a lot of painting... and I mean a lot. I am about to do some hard lines as was considering galvanized after weighing the pros, cons and my rudimentary skills. Is it something about newer galvanized pipe that is the issue? Galvanizing technique? Chinese stuff? curious to hear perspectives

 

[RMR&C]

I am curious as well....any experts out there? I am thinking of going this route but have not heard of any pros or cons. I have a cutter and threader so this would be fairly simple.

On the other hand, any body/paint shops using black iron pipe? Any rust issues? TIA

 

[tonydanzah]

semi brake air line is the way to go

 

[katit]

Copper here, routed all in-wall's and one drop on a ceiling for reel. 3/4 soldered all in 2 evenings. Spent 2x time doing straight run to plumb gas to the kitchen stove. I say no to black pipe

 

[mslisaj]

We installed a total of 75' of 1" black pipe and it lasted for 20 years until we moved out of the building. It was a custom install and every stick was cut to length and threaded. Yes there were leaks to chase down but never had a problem and we were painting cars weekly off this system without any problem. Our new shop will take about 150' and we're going to go with 3/4" runs and 1/2" down pipes. This we're going to do in copper. Yea, we're saving out money to do it but it will be a lot easier..........

Wish someone would come out with the 3/4" or 1" coils of press tubing and slip fittings. But would probably have to hock the shop to afford it. So copper it will be.............

 

[Licensed to kill]

OK, so, stupid question of the day. If you are doing a 40X60 shop and you run the piping around the shop IE down a 60 foot wall, across the end 40ft wall and up the other 60 ft wall you have 160 feet of pipe. With the compressor in either of the back corners, you will have a max of 100" to one end of the pipe run (60ft to the other end) and if you have the compressor in a front corner (by the door) you will have a full 160 ft around to the far end. 3/4 pipe would impart a fair bit of restriction on those kinds of distances so 1" should be a minimum. HOWEVER, what if 2" was used instead. It would not look very trick BUT, not only would you have full working pressure and volume at the farthest reaches, you would also gain 27 gallons of capacity on 160ft. 3/4" would only give you 4.5 gallons and 1" only 7.2. With a 60 gallon tank on the compressor you almost gain another 50%. OK, another stupid question, rather than running the piping along the wall and having drops at each coupler with a ball valve drain, why couldn't you run the pipe along the base board and have the take offs run UP to the coupler. Then you could just use one ball valve at the end of the pipe to drain water from the whole line at once rather than at individual take offs? Just wondering as I will be plumbing my shop for air shortly.

 

[RMR&C]

Hmmm, 2" iron pipe would weigh a ton.......you would have to run it along the floor. Or hire a crane. I don't see why that wouldn't work though, as long as it was sloped to drain at the end. My 40x60 currently has the pipe (pvc) around the ceiling perimeter....the only trap that ever has water is the one closest to the compressor. When I redo it, it will have only one run with maybe 2 drops with the pipe at 4' up the wall. Less is more...

 

[seabeckredneck]

Yes, like GeorgiaHybrid said, use the Type "L" copper and they sell it at both Home Depot and Lowes. I just finished my garage air in 3/4" copper and had never done plumbing before. I have a Family Handyman magazine that has an article on how to do it. When I was done I had no leaks! (I was quite surprised) and it looks great.
Good luck on your project!

 

[mslisaj]

To Licensed to Kill..........

You make great points on all accounts. As I mentioned in my post we ran 1" steel pipe and used it for years with no problem. When it was installed we were very confident we were getting maximum flow. But after years of use the reality was we did not have any equipment that actually needed that high volume of air even with multiple techs running equipment at the same time. We had a five horsepower compressor with an 80 gallon receiver. Sure the bigger the pipe the better and if you really wanted to do it right you could add another receiver at the end of any one of your runs and now you have some real capacity. If you have a lot of air use and will have multiple devices pulling air at the same time that 2" line would probably be the way to go......

My comments for my new shop are based on the fact that I didn't really need all the huge 1" pipe I had in the years I was in business. Now I'm fitting out my home shop and I figured 3/4" copper with the smoothness of the lines and fittings and 1/2" drops would work for me. I can't run the piping along the floor do to different obstructions and the compressor is in the middle of the building and the air system when completed will actually be in a H shape.

But all your points are well taken and would work nicely if you want to put in that much work and expense to get a MAX air system...........

Lisa

 

[dougmac]

My vote ..... Copper...

- Easy to install.
- If no hoses are hooked up.... I can leave the power off to my compressor for over two weeks, then turn it on and the motor wont start because the air hasn't bled down enough to cycle on .

 

[gmhill33]

Dumb question.

Can you run the pipe up the wall and then add how ever many drops that you need?

I have a room on the back of the garage for the air compressor (not so noisy). I will come through the wall into the garage at about 7' or so but I want the copper pipe (that is what I've decided to go with) running around the garage at about 10' or so. SO the question was can I come through the wall at 7' and the go up the wall to 10' with out losing to much (if any) air pressure?


Thanks for helping with my many dumb questions.

Gary

 

[bc'z]

yes you can

 

[rhastings80]

I had to move a gas line in my house and used black pipe since that what I already have. It was a total pain. I did take out a permit with the city and it passed. I had home depot cut and thread the pipe. I had to go back 3 times to get it right. The first two guys didn't know how to thread the pipe. If you do have any threaded and cut at the store make sure you test all threads and fittings to save yourself frustration. It also seems like the fittings at the big box stores are super cheap quality and made in china. If you buy pre-cut lengths all make sure the threads are not trashed.

 

[OccupantRJ]

Power wirebrushing the threads of hard pipe in the direction of the threads will give a better fit and seal. It smooths out the burrs that occur during threading, and does make a difference. When hand threading, I back the die up at least every three pulls of the threader handle to break the chips. Keep it flooded with cutting oil. Teflon paste will usually make a good joint, and I sometimes use Rectorseal, Indian Head gasket shellac, or teflon tape. Overtightening a joint can actually swage the pipe down, make the taper concave, and cause it to leak. That is, if it doesn't crack the fitting.

 

[Brust]

plastic airline kits?

Why not use these http://www.harborfreight.com/complete-garage-air-kit-66747.html? Got one of the HF kits and have run it inside the drywall of the garage. It's 3/8" od, so certainly not big enough for a huge shop, but for a homeowner using one tool at a time, I'd think it would be perfect.