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Tip: Plumbing the Garage for Air

larrynew

Well Known Member
Here's a simple description of how I plumbed the garage for air. YMMV.

Snapshot_20100325_2.jpg


1. I used 3/4" galvanized steel piping for the perimeter and 1/2" for each drop leg. I tried to slope the pipe toward every drop to help control moisture. Water goes down, air goes up. On some of the drops, I just used a 3/4" Tee.

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2. I used several unions in the perimeter piping. Unions allow you to disconnect the two pipes on either side of the union without turning either pipe to unscrew it. I was able to build the system in sections and put them up one section at a time. It really made it easier to trouble shoot leaks since I could just remove one section and work on it while leaving the rest in place.

Snapshot_20100325_1.jpg


3. The basic set-up of each drop is show above. I used 1/2" unions on each branch-off from the drop to allow me to remove it without having to twist pipe. I used brass ball valves on the bottom of each drop as that's where the water will collect. On some of the drops, I added a male air fitting after the ball valve which allows me to add another compressor to the system. If you have a different size filter (3/8" is common), just change the reducer and nipple coming out of the union to that size. On the branch above, I have an oiler in addition to the filter/regulator because this is the place I run most of my air tools. That saves me from having to remember to add oil drops to every tool before use. The other drops don't have an oiler.


4. I used Rector Seal #5 pipe thread sealant from Home Depot and teflon tape for every joint. I first wrapped the threads with teflon tape and then "painted" the Rector Seal over the teflon tape. I tried several variations and this way works great. I used a spray bottle with slightly soapy water to test all the joints and I don't get any leaks.


5. For my compressor hook-up, I just have a drop like shown above but instead of a filter, I have a short length of air hose that attaches to the reducer fitting on the union. By keeping all the drops standard, I can move the compressor or any fitting like the one with the oiler to any location in the garage I want by just disconnecting the union.


6. I have 5 drops in my system. I put the drop I plan on painting from on the last leg. My tool drop is the next to the last. When I bleed each drop, I get very little moisture after the first drop from the compressor which is the way it's supposed to work. There are fancier ways to do this but it works well for me. Some folks have a loop type arrangement at each drop where the pipe first goes up and then back around and down but I didn't have enough room against the wall plus it would add several additional joints for each drop. I didn't keep receipts but it was about $200.
 
Compressor, hose reel, and lightweight air hose kit

I have a belt-driven piston compressor with a 40 gallon vertical tank that I set up against the front wall of the garage in between the two roll-up doors. I mounted a hose reel above the compressor on a 2 x 4 attached to the door tracks, and fed the reel with a short hose connedted to a combo filter-regulator on the tank outlet. Both the compressor and the hose reel came from Northern Tool.

The tank volume is large enough relative to the average flow rate that the air has time to cool and condense water inside the tank. I replaced the tank drain valve with a ball valve and a short piece of hose so that I can easily drain the water outside every month or so. I have never seen any water in the hose from the reel.

The hose reel has enough hose to reach anywhere in my garage. I simply pull it out and let it lay on the floor. I bought a lightweight air hose kit from Cleveland Aircraft Tool that lets me leave the heavy hose and coupler on the floor when using hand tools.

That's it. Compressor, hose reel, and lightweight hose kit. This simple setup has worked well for me for the past six years.
 
I would encourage use of copper instead of steel.

Yes, it is expensive, but Copper conducts heat many times greater than steel. Assuming you are conducting that heat into the air surrounding your piping and the air is capable, cold enough, to absorb that heat.
Anything you can do to condense the compressed air and evacuate the resultant water before it gets to your outlet will help keep it from condensing in your hose, tools, or paint gun. That means cooling the air to the best of your ability. Copper does this much better than steel.

Generic water separators only take care of what is already condensed.

There is no substitute for distance to help with cooling either.

Cool air means less suspended moisture to come out in condensation = longer tool life, less risk of water in your painting processes, etc...

Not being picky as your installation is very sanitary. I would just have chosen different materials. I am sure your system will work just fine but it is the type of thing that until you know the difference between really dry air, and almost dry air, you wont know how much easier some things like painting might become.
 
Like I mentioned...

I used schedule 40 plastic pipe and it's worked fine for the last 6 years.

.... probably works just "fine", but until you know the difference you dont know what "fine" vs "really good" is (not you specifically...).
System type or material may make little difference to anyone just operating air tools, but if you are going to paint HVLP, or do anything like
Soda Blasting, you need all of the help you can get cooling and drying the air.

Lots of choices for people. Your results may vary!
 
My PVC pipe blew up. Real exciting. First you hear it explode and pieces flying, then the rush of air comes instantaneously after that, then the compressor comes on, all in a split second. Then you go buy copper or steel.

At my present place I used copper and never get a bit of moisture after about a 28 foot run.
 
Using Pex for running air lines is cheap and works well, won't explode if it splits. One can replace it every ten years and still be money ahead over black pipe or copper.
 
Asco valve

We're moving in about 3 weeks, 3 car garage!
I plan on installing an asco Valve in the system
wired to the light switch, so that when the lights
are off there will be no pressure in the system
so even if there are any small leaks the compresser
won't come on in the middle of the night. Is this a
good idea?
 
We're moving in about 3 weeks, 3 car garage!
I plan on installing an asco Valve in the system
wired to the light switch, so that when the lights
are off there will be no pressure in the system
so even if there are any small leaks the compresser
won't come on in the middle of the night. Is this a
good idea?

Sounds like a good idea, but the ASCO valve would typically have a significant pressure drop across it when you're pulling a lot of air through the piping. For the small jobs, you'd probably not see a problem. Not knowing the size of your piping or the flow coefficient of your ASCO valve, I cannot say for sure how much pressure drop your system would have at the valve you describe.

Why not install just a simple ball valve for on-off control of the system? I use one for that purpose every time I leave my shop, and I turn off the compressor with its switch for the same reason you list. I do have small leaks in my piping, so I isolate the storage tank so the compressor doesn't cycle while I am away. A single ball valve is much simpler to install than a 120 volt remotely controlled valve.
 
Rupture of PVC Pipe in Compressed Air System

My PVC pipe blew up. Real exciting. First you hear it explode and pieces flying, then the rush of air comes instantaneously after that, then the compressor comes on, all in a split second. Then you go buy copper or steel.

At my present place I used copper and never get a bit of moisture after about a 28 foot run.

Interesting. I believe you are the first RV builder to report rupture of PVC piping. I used it in my garage but when I built my detached shop, I installed carbon steel piping. As I said in another thread, I could not find any piping code in the United States that allowed PVC piping for compressed air except when that piping is buried at least 12 inches below the soil. As a registered Professional Engineer, I could not conscientiously install PVC piping for compressed air at my house, especially with 5 grandchildren who occasionally visit me in my shop.
 
Some Home Air Piping Do's and Don'ts

If you're using copper, DON'T use Type M. It's for residential water piping and is not approved for compressed gasses. Use only Type K or L for compressed air.

Don't use PVC for any compressed air system. It's not approved or recommended by any U.S. piping code for compressed air. "But I've been using it in my shop for years without a problem," you say. Yes, and I had a friend who did snap rolls on takeoff for years without a problem, until one day... Enough said.

Galvanized carbon steel pipe is not usually recommended for compressed air, especially if air tools are to be used in the system. The galvanization is a coating and as such can be released on the inside of the piping resulting in contamination and clogging of the air tool unless downstream filters are installed at each air tool tie in location. Also, threading of the pipe at connections results in sites for rust to develop. The extra cost of the galvanized pipe is not warranted, IMO.

A good pipe seal "dope" is preferred over Teflon tape for systems using air tools because the Teflon tape can be cut by the threads and become a contaminant for air tools downstream. None of my air piping and none of my air tools use Teflon tape for thread sealing.

Carbon steel pipe aka "black iron" can develop rust and contaminate air tools unless the design allows for removal of water. The air is heated when it is compressed. When the air enters the cooler piping system, either copper or steel, the moisture in the warm compressed air condenses. A good inline filter which can be "blown down" each day is necessary. Also, the design of the piping should include a slope of approximately 1 inch per 10 feet of run away from the compressor. At each drop, the tee should point UP from the main run and then at the end of the vertical drop a ball valve should be installed to drain any contaminant in that branch. A ball valve should be installed in a vertical drop at the end of the system to "blow down" the entire system once a day. Definition: "Blow down" as used in this post simply means a quick burst to allow air and any contaminants to vent the system.

It's true that a perfectly good RV can be built with a small compressor and a rubber hose for the various air tools needed to build an RV. I saw an RV-6 many years ago that was built that way. It's really not necessary to build an industrial quality air system in your home "RV factory." But there are some safety considerations (like don't use PVC pipe!) and there are some other practical considerations which can help you build a better air supply system for your home workshop. YMMV.

These are my opinions based on a lot of engineering experience and a lot of reading. Hopefully they will cause you to seriously ponder the many decisions necessary to design and build a compressed air system for your home RV shop. Every system is a compromise, but the main concern here is don't compromise safety.
 
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Very good summary

If you're using copper, DON'T use Type M. It's for residential water piping and is not approved for compressed gasses. Use only Type K or L for compressed air.

Don't use PVC for any compressed air system. It's not approved or recommended by any U.S. piping code for compressed air. "But I've been using it in my shop for years without a problem," you say. Yes, and I had a friend who did snap rolls on takeoff for years without a problem, until one day... Enough said.

Galvanized carbon steel pipe is not usually recommended for compressed air, especially if air tools are to be used in the system. The galvanization is a coating and as such can be released on the inside of the piping resulting in contamination and clogging of the air tool unless downstream filters are installed at each air tool tie in location. Also, threading of the pipe at connections results in sites for rust to develop. The extra cost of the galvanized pipe is not warranted, IMO.

A good pipe seal "dope" is preferred over Teflon tape for systems using air tools because the Teflon tape can be cut by the threads and become a contaminant for air tools downstream. None of my air piping and none of my air tools use Teflon tape for thread sealing.

Carbon steel pipe aka "black iron" can develop rust and contaminate air tools unless the design allows for removal of water. The air is heated when it is compressed. When the air enters the cooler piping system, either copper or steel, the moisture in the warm compressed air condenses. A good inline filter which can be "blown down" each day is necessary. Also, the design of the piping should include a slope of approximately 1 inch per 10 feet of run away from the compressor. At each drop, the tee should point UP from the main run and then at the end of the vertical drop a ball valve should be installed to drain any contaminant in that branch. A ball valve should be installed in a vertical drop at the end of the system to "blow down" the entire system once a day. Definition: "Blow down" as used in this post simply means a quick burst to allow air and any contaminants to vent the system.

It's true that a perfectly good RV can be built with a small compressor and a rubber hose for the various air tools needed to build an RV. I saw an RV-6 many years ago that was built that way. It's really not necessary to build an industrial quality air system in your home "RV factory." But there are some safety considerations (like don't use PVC pipe!) and there are some other practical considerations which can help you build a better air supply system for your home workshop. YMMV.

These are my opinions based on a lot of engineering experience and a lot of reading. Hopefully they will cause you to seriously ponder the many decisions necessary to design and build a compressed air system for your home RV shop. Every system is a compromise, but the main concern here is don't compromise safety.

I still see folks commenting that there system is just fine as they dont see water in the traps. Just because there is no water in the trap does not mean there is no water in the air. As you stated, doesnt make a difference if your just using air tools. My Soda Blaster is super critical to have dry air for the Soda. Not much need for that building an RV.
PS - I have a neighbor with PVC. It split and blew up. It was also installed above sheet rock with many convenient drops. Nice system, does'nt work, and is now unrepairable.
 
I just finished plumbing my entire house with PEX and I have about 50 feet extra. Is this stuff and sharkbite fittings OK to use? It would be much easier than AAAA1 class, schedule 160, monel, seal welded pipe.:D
 
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Good advice

Sounds like a good idea, but the ASCO valve would typically have a significant pressure drop across it when you're pulling a lot of air through the piping. For the small jobs, you'd probably not see a problem. Not knowing the size of your piping or the flow coefficient of your ASCO valve, I cannot say for sure how much pressure drop your system would have at the valve you describe.

Why not install just a simple ball valve for on-off control of the system? I use one for that purpose every time I leave my shop, and I turn off the compressor with its switch for the same reason you list. I do have small leaks in my piping, so I isolate the storage tank so the compressor doesn't cycle while I am away. A single ball valve is much simpler to install than a 120 volt remotely controlled valve.
My plan was to install an oversized valve, I like the ball valve for its simplicity, but I'm not sure I could trust my memory to turn the ball valve as well as I remember to turn off the lights (that's the reason to wire it with the lights, maybe in seires with a dedacated switch) or as likely I'll just trip over hoses until I get tired of that
 
Don't use PVC for any compressed air system. It's not approved or recommended by any U.S. piping code for compressed air. "But I've been using it in my shop for years without a problem," you say. Yes, and I had a friend who did snap rolls on takeoff for years without a problem, until one day... Enough said.

I knew I should have kept my mouth shut. :rolleyes:

I was just throwing out a data point. So, while PVC is not recommended or made for use with compressed air systems, that's what I did and it's hasn't failed in 6 years. I got that idea from a friend who's father did the same thing in his garage for years. The max working pressure for a Schedule 40 pipe is more than double what my compressor can even put out. Yes, the glue could get old and let go or leak but once again, this is just a data point and I'm not advocating anything here.

In hindsight, I could have easily just used my rubber hose draped across the floor. There really wasn't a need for me to plumb it in at all.

A friend of mine likes to say (cleaned up for VAF use), opinions are like rear ends, everybody has one and they all stink but yours! :)
 
Don't feel bad Kelly - I have a really simple system - I just buy air hoses and "T"-connectors. They are zip-tied to conduit up on the walls of our hangar, and then I have drops where I need them. Don't have to make any kind of ends, and air hose is cheap - a few hoses and my 40x50 hanagr has air everywhere.

Paul
 
I just finished plumbing my entire house with PEX and I have about 50 feet extra. Is this stuff and sharkbite fittings OK to use? It would be much easier than AAAA1 class, schedule 160, monel, seal welded pipe.:D

I bought a 100ft roll a few weeks ago to run an air line to my CNC lathe and it cost $28 at Lowes. I already had the crimpers and a bunch of fittings.
 
Using PEX for air

I bought a 100ft roll a few weeks ago to run an air line to my CNC lathe and it cost $28 at Lowes. I already had the crimpers and a bunch of fittings.

I have to admit that I know very little about PEX other than seeing it being installed on an episode of "This Old House" and being very impressed. That, and this post prompted me to find out more, where I came across the following comment:

"PEX tubing cannot be used in applications exposed to sunlight, as it degrades fairly rapidly. Prior to installation it must be stored away from light, and needs to be shielded from daylight after installation. Leaving it exposed to direct sunlight for as little as 30 days may result in premature failure of the tubing due to embrittlement."

If your workshop has skylights that let UV through (as does mine) this looks like a show stopper for PEX. :(
 
PEX tubing not rated for air systems

Per the manufacturer(s) of PEX tubing, it is not rated (approved) for compressed air systems. I have a friend with a SCH 40 1/2 inch PVC system in his garage. His answer when I questioned him about it was "60 psi is 60 psi."

There is a LOT of difference in the energy stored in a 60 PSI air system versus a 60 PSI water system. Think of the air system as a compressed spring. That's why high pressure hydraulic systems are so common. Hydraulic fluid at 3,000 psi has its risks, but can you imagine the danger of compressed air at 3000 psi?:eek: I hope you can appreciate that danger.

PEX is used extensively and safely in indoor and/or underground water systems. The concern with PEX for compressed air systems is the possibility of sudden rupture similar to PVC.

You may get by with it for a short time, but how long is the fuse on that time bomb?

This has nothing to do with smelly opinions; it has everything to do with the laws of physics. If your neighbor has the opinion you should fly your RV on its maiden flight without checking weight and balance, would you listen to him or do what the laws of physics and thousands of other aviators have done? Other people's opinions kill and maim people every day.

Just be safe.
 
I believe at least -- from reading online accounts elsewhere -- that PEX at least is likely to "split" instead of "explode". Not first hand though.
 
The pex I use in my shop is rated 160psi at 73 deg. F. I wont lose any sleep over using it for shop air. :) All one has to do is try to break it by bending it repeatedly to see what the burst characteristics are like.
 
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