water in my air line

  • Advertise with us

« back to Woodworking Skill Share forum

Forum topic by thewoodmaster posted 07-08-2011 04:56 AM 1751 views 0 times favorited 9 replies Add to Favorites Watch
View thewoodmaster's profile


62 posts in 3754 days

07-08-2011 04:56 AM

I have a dewalt 5 gal air compressor that I have stored in a cabinet under my work table. I ran some PVC from the inside of the cabinet to the outside where I can hook up to it with a hose. I am having some issues with water/rust in the air. I don’t empty the compressor every day, like I should, but I also don’t use it every day.

What should I do to eliminate this water in the line?

-- dan "insert pithy woodworking coment here"

9 replies so far

View FirehouseWoodworking's profile


756 posts in 3834 days

#1 posted 07-08-2011 05:16 AM

You could put a water trap in-line either where you plug in your airline or where the compressor is plugged into your system. They are commercially available and not that expensive.

An alternative is to build your own in your piping system, usually right before where you plug in your airline. It looks like a capital “U”, about 8” – 12” tall. At the bottom of the “U” (the horizontal portion), you plumb in a quarter turn valve. The moisture will accumulate along the bottom of the “U” allowing the air to bypass the accumulated moisture. At the start of each day, make sure your compressor charges the system, and then open the valve. That will purge all the moisyure. I have plumbed one of these traps at each of my system’s outlets, in addition to the commercial trap at the compressor.

As an additional thought, why not plumb in an extension to the valve at the bottom of your compressor’s tank? I did it on my large compressor and there’s no longer the need to bend down and reach under to release the accumulated water. I replaced the compressor’s screw valve with a quarter turn valve to make it that much easier.

Good luck. Cheers!

-- Dave; Lansing, Kansas

View Grandpa's profile


3263 posts in 3237 days

#2 posted 07-08-2011 05:41 AM

I have one of those Dewalt compressors like the woodmaster is discussing. the drain valve for the tank is not located in the bottom of the tank. You have to raise it (at least mine is this way) and prop it up on the front to get the valve to the bottom. I don’t like that feature at all. I have wondered if a drip leg wouldn’t work in a plumbed system. They use them on gas lines all the time. they are a requirement on natural gas lines. Just put a T in the line and run the air up and the leg goes down. Add a ball valve on the bottom to blow the moisture once in awhile. This still doesn’t get rid of the moisture in the tank though. Has anyone ever tried the automatic drain valves on their tank? I have seen them but never tried on. I really don’t know how or if they work.

View auggy53's profile


159 posts in 3241 days

#3 posted 07-08-2011 05:46 AM

you can buy a drier to go inline that will help also.

-- rick

View crank49's profile


4032 posts in 3532 days

#4 posted 07-08-2011 05:56 AM

Some of the automatic drains work with a float, kinda like the valve in a toilet tank, but compressed into a small valve housing.

View Earlextech's profile


1162 posts in 3252 days

#5 posted 07-08-2011 11:13 PM

Firehouse is right on!

-- Sam Hamory - The project is never finished until its "Finished"!

View JimDaddyO's profile


625 posts in 3640 days

#6 posted 07-09-2011 04:46 PM

+1 on Firehouse’s suggestion. If you want to go a step further for when you spray paint, etc. where you want even less moisture in the lines, make the U like Firehouse said, and mount it on the wall so the bottom 2/3 of the U is at the right height to sit in a bucket. Put the bucket under (around?) the U and fill it with ice, this will make the humidity in the line condense and gather in the bottom of the U. The act of compressing air heats it up, and thus it carries more humidity, cooling it makes it drop the excess humidity.

-- my blog: my You Tube channel:

View LONGHAIR's profile


94 posts in 4376 days

#7 posted 07-09-2011 05:37 PM

Then doesn’t this collected water just block the bottom of the U? much like a P trap in plumbing…then just get pushed by the air behind it?
This could only work if there was a way for the air to by-pass it…thus defeating it too?
Besides, with fairly decent air movement, the air would only be in the ice/U for a fraction of a second. That’s not going to do much for cooling.

The best way that I have seen it to have several “loops” of the copper tubing nunununununu with the air exiting the top of the last u and drain valves at the bottom of all of them. This longer “exposure” to the ambient air cools the compressed air slowly and give it more places to collect (and be drained off) A simple dessicant dryer at the end should be good at that point. You will notice that there is less water in each successive loop and learn to deal with it accordingly.
Not exactly cheap, but it does work….for a lot less than an actual commercially available dryer. It take no power to run, requires no “media” nor maintenence (other than draining the valves, but those can be automated too.)

View jimmypaul's profile


8 posts in 3075 days

#8 posted 07-09-2011 08:14 PM

I have a drain valve screwed into mine that has a long cable attached to it…. All you gotta do is pull the cable an it spits out the water … Got mine from NAPA auto parts … they use them on the Air Tanks on most Big Rigs….. If they dont have auto spitters on them …... An the water trap at the outlet side of the compresser is a good idea to have too….. Also an auto oiler set up with quick disconnects ,, So if iam using air guns an such all I gotta do is just connect it in line…..

-- JimmyPaul Florida

View reggiek's profile


2240 posts in 3831 days

#9 posted 07-09-2011 09:03 PM

Also, you should run the tank with the release valve open for a few minutes to dry out the tank – basically blow air out the valve….this will slow down the rust growth. You should do this every couple of days but I have seen folks get away with once a week or so. The next thing is a filter as mentioned above….this will protect your tools…but not the compressor….best bet for it is the dry out mentioned above….unless you want to put a dehumidifier in front of the intakes (I don’t even think that would help as air coming in has water vapor no matter what you do with it.)

-- Woodworking.....My small slice of heaven!

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics