High or Low Runs for Shop Air Plumbing?

Hi.

I have a question about something that is probably a bad idea. There is probably an obvious answer why this shouldn’t be done the way this occurred to me. I am sketching out plans for air plumbing in my shop. I see many articles that say that when the drops are made from the main pipe at the ceiling, there should be a “J” at the bottom of each drop to catch any moisture that might make it into the air hose.

Has anyone run their main air lines low, just above the baseboard? It seems that then most moisture would stay down in the main line. I would have to make one rise and then a drop go over a pedestrian door. I plan on installing some sort of anti-moisture device when I put my compressor and plumbing in my garage.

The air system will be used for operating tools and a blast cabinet. I would like to be able to use the system to operate a paint gun occasionally as well. I am buying a Champion 19.1CFM, 5 HP, 80-Gallon, Stationary air compressor.

Am I overthinking again?

Thank you

Bob

Just a suggestion, if u can put the compressor in the house (basement or crawlspace) you would thank yourself.

Your wife will eventually get used to it

If you guarantee that the air entering the piping holds so little moisture that no moisture will precipitate, even in an air tool, put the piping low. Since that condition is virtually impossible to achieve, put the piping up high. The attached .jpg is a scan from the General Installation Instructions literature that came with my Champion brand compressor. It takes more pipe, fittings, valves, etc. to do it well. Lesser is cheaper (and wetter). Suit yourself.

When I built my shop I ran the air lines under the floor. If there is any moisture getting in there at all, during the night it condenses and runs to the low spot. Then all day long it spits it out whenever there is a slug big enough, or enough flow to move it.

When I redid the airlines, I ran them high, sloping down a bit to a vertical T. The downward leg of the T went to a drain tap, the upward one stepped back up to plate height and then started a new downward run. Any air use was tapped off the top of the vertical. That did trap a lot of water.

Then I got a screw compressor with a good refrigerated dryer. Now there is no water in anything to trap - every drain tap is totally dry always.

So - get a good drier and run the lines wherever you want, or else run the lines high.

+1 on getting an air drier, esp for blast cabinet(s) and paint. Folks might argue for pages about what pipe to use if you don't. (BI vs GI vs copper vs poly, etc ... )

Good idea to take all drops 'up out and down' (see post #3) in case the drier is 'down' & then bypassed. Drip T (sideways) at the bottom of the last vertical before a tap/take-off, capped or w/shut-off. Slope lines downhill and terminate mains with trap or drain cock. Easy peasy.

I have designed, re-designed, and installed many air systems, most in facilities far more critical than a machine shop. I have always installed the main run just below the ceiling or roof level.

AND with a slight slope BACK toward the compressor/tank/filter system. That way, any moisture in the line will drain back to the tank or filter jars where it can be drained off.

I once encountered an existing system where there was a two story high, vertical water collection column that went down from the roof level to below the first floor, in an elevator shaft. It had a drain valve at the bottom. Then back up to the second floor where the air was used. The theory of that design was to collect the water in that vertical column and drain it off regularly. It worked. The water DID COLLECT in that vertical column and every bit of air went THROUGH that standing water, ensuring that it picked up at least some moisture along the way. The system was constantly delivering wet air with more moisture than simple filter jars could take out at the point of use.

Along with some other changes, I completely eliminated that column. The run across the roof did slope backward to the tank/filter area, which also included a refrigeration style dryer. After the system was redesigned, there was never another single drop of water found anywhere past the refrigeration dryer.

Most shops do not have refrigeration dryers and that makes proper design even more critical. If you run your line along the floor, water WILL accumulate there and it WILL be reabsorbed by the air that passes over or through it. You will always have water in the air that is delivered.

If you run your line overhead, above the compressor/tank/filters and above the point of delivery and slope it backwards, you will have much less water at the point of delivery. The drops that tee out of the main line in an upward direction and then make a U turn downward will help keep the water out of the drop. Place a Tee in the drop line and extending the drop line STRAIGHT down, below this Tee so any residual moisture can then that extension below the level where the air is used so the air does not pass through it. Put a drain valve on the bottom of each of these drops.

If that "horizontal" run can be in an air conditioned or unheated, cool space, so much the better. But not below freezing temperature, of course.

^^ Slope it.
That's what we do also.

I find myself wondering what effect the temperature gradient has on the lines running low vs high. Up high in a shop, the air temp will be higher, will keep the pipe warmer and have less tendency to cool the air and condense water. Down low the pipe will be cooler and have more tendency to cool the air and condense the water.

So running the lines high will keep the air warmer, and make it condense farther downstream? (Unless it's very dry before entering the lines, in which case low vs high shouldn't matter?)

Has this ever been tested?

We may have the same compressor, first we added a commercial radiator with a fan between the compressor and tank. The air comes out at the same temp as the surrounding air. This dumps a majority of the water outside before it reaches the tank. We still had "wet" air and added a refrigerated drier that gets the air down to a 41 degree dew point. Now we have no problems, the traps never have any water and now seem unnecessary.
If the shop ever got down to 32 degrees then they would collect water again, of course I would move further south if that happened.

- Slope the line, but down in the direction of air flow.
-Don't forget to run a big loop from the compressor, so each tap has air flow from two directions. This way the pressure will not fluctuate as much to a user at the end of the line (when someone in-be-tween hits the blow off gun).
- I you run anything with air bearings a dryer is a must.