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Draining air tank

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drooartz

drooartz

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A question for y'all -- I have a 35 gallon Craftsman compressor/air tank. The owners manual says (if I remember correctly) to empty it after each use, including opening up the drain valve on the bottom to let out any moisture. Now, I don't use this all that often -- can go weeks between uses -- so this is what I have been doing.

I mentioned this to a friend of mine, and he told me that he never does that. He runs a shop (trade show exhibits and such) and has had a few compressors over the years, including heavy duty commercial units. All these have lasted quite well without the constant tank draining.

So should I save energy and keep the tank full?
 
I drain mine all the time. From the amount of rusty water that comes out each time, I'd say if you left pressurized air with water inside for long periods, eventually there's going to be lots of rust. I guess it depends on whether you want to take the risk of having the tank rust to the point where it leaks or worse, it bursts. Since the drain is at the lowest point, I suppose it's also possible the drain could get stuck with rust, and then it's much more difficult to drain the water.
 
Unless you have a fail safe type of water trap drain to remove condensate from the tank it will collect water and rust out after a while. There are automatic systems on the market that will do this for you and not waste all the energy and saved up pressure for you but I have not tried one yet. It's on my list of items to do. One of the used compressors I bought recently had about two gallons of rusty water filled with metallic flakes.
 
Draining it is not a bad thing, Drew. Mebbe every other time ya use it.

Here in Flor-eyeda we live in high humidity year-round. I have to keep two seperators and a drain valve. On a typical day I can expect to drain half a pint from the manifold and another from the in-line seperator. A real PITA, but if you're gonna use it, no sense in introducing water into tools or in your paint work! Tank corrosion would be your biggest concern, I would suspect.

Oh, and my compressor is likely older than you and I together. The "tank" arrangement is three diving tank sized fire extinguisher bottles, inverted and connected together with a "black pipe" manifold. Flat against one of the walls inside the garage: whole affair is less than 14" deep.
 
I blow off the moisture as often as I can remember to. Here in KY, although humid, there is not much water draining off. I don't pressure it down, I just open the valve a couple seconds until it blows clean and then shut it.
Have a nice day
Steve
 
Utah (other than this winter, geesh) is a very dry climate. I'll have to try just blowing off the little valve on the bottom without draining all the pressure. For as little as it is used now, the extra time to pressure it up isn't that big of a deal.

I like the concept of your tank setup, Doc. Much more compact than my single honking tank-on-wheels.
 
Drew:
I drain my air tank {of water} frequently. Sometimes even while or during me using it. My compressor and tank are hard lined to a homebrew manifold in my garage it too has water traps and dryers on all of the air ports. And you are right about dry climate here, but never the less my system does accumulate moisture. When i`m using my air system I never drain off all of the pressure. Like mentioned above, I just drain off the moisture. B.T.W. my homebrew manifold isn`t completely air tight and if the compressor is not in use it will drain off all of the air pressure within about two days.
After you use your compressor a while you will get a feel for how often you need to drain the moisture off. When I do not use my system for long periods I drain everything off, air and all.
 
I'll ditto draining any accumulated water at every use. If you're going to let it sit for a long time, then I feel letting the air out is a good idea as well. But if it will only be a few days before it's used again, then you're probably safe only draining the water.

The reason for draining the air is that it continues to condense water long after you quit using the unit. If I drain water last thing at night, then let it sit overnight with pressure in it; in the morning there is more water in the bottom of the tank.

Another solution might be to rig a catch can below the main tank, to hold a small amount of water between uses.
 
Drew,
I've been using a rather smallish (5.7 SCFM, 28 gallon) upright for a couple years. Since I retired I usually get out to the shop Mon-Fri and rarely a day goes by that I don't used compressed air for something. I did pretty good on draining my tank for a while, then it bacame one of those deals where "I'll do it tomorrow". Of course, tomorrow came two months later.

The main reason I don't do it is because of the lack of easy access to the drain cock. It's a vertical tank and of course, the drain has to be on the bottom. It's also on wheels that are just not tall enough to let you get your hand under there easily.

Just yesterday I bought a new compressor for the shop I'm building. It's a stationary upright three cylinder, 14 SCFM, with an 80 gallon tank. First thing I'm going to do, before bolting it to the floor, is remove the drain cock and plumb in an elbow to a flex line to a handle type valve to a pipe that exits the compressor room through an outside wall. Every day or two I'll open the valve and let it blow out any condensation...all without having to even bend down.

Then I'll retrofit my smaller compressor similarly since I'll be keeping it for use in my wood shop.

Ray
 
I drain the air after every use. I also drain the water based on usage.
 
This little unit is well worth it. Bought out of a scrap yard. We use them on all the air vessels in the chemical plants.
 
mccalebr said:
Drew,
First thing I'm going to do, before bolting it to the floor, is remove the drain cock and plumb in an elbow to a flex line to a handle type valve to a pipe that exits the compressor room through an outside wall. Every day or two I'll open the valve and let it blow out any condensation...all without having to even bend down.
Click to expand...

I have a similar arrangement: I removed the tap, put in a 30' coily hose and a blow gun. Every day I give the blow gun a few squeezes and blast out the water.

The coily hose is convenient to inflate tires as well (with the proper fitting)
 
I drain about once a year whether it needs it or not - been using it since 1993.
 
mccalebr said:
The main reason I don't do it is because of the lack of easy access to the drain cock. It's a vertical tank and of course, the drain has to be on the bottom. It's also on wheels that are just not tall enough to let you get your hand under there easily.
Click to expand...
I removed the drain cock, and plumbed ordinary pipe to a ball valve where I can operate it with my toe. Didn't go as far as routing it outside the shop (since it's a portable unit and I do sometimes move it) or using flex line, but it sure makes it easy to blow out some water. And the pipe provides a small catch can, so there can be some water inside but not in the main tank.
 
Thanks all for the tips. I'm going to keep draining it out for now, since it can be weeks between uses for me. When I get to redesigning the workspace in my garage I'm going to build a platform for the compressor, so it will sit a bit higher off the ground. That way the drain valve will be easier to reach.
 
Local compressor service place told me that more than once they have had someone bring in a "Broken Compressor" with the tank more than half full of water.

Marv J
 
Just picked up a do hickey that replaces the drain valve and when the pressure drops below 8 psi it automatically opens and drains the tank. $14 cdn
 
So, tell us what that "do hickey" is so we can grab one!
 
I love Harbor Freight!
 
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