Thread: How can I keep moisture out of compressor?

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I pulled of a plug off of my compressor and notice a lot of rust in my new compressor. So , how can I keep the moisture down inside the tank? Maybe a couple of sprays of DW-40, not doing any painting any time soon. I do drain it regularly also.

Another question maybe you can answer, Why are the air filters on compressors so restrictive? Are they meant to be like that, or can I put a bigger air filter with no problems ?

Moisture is a natural by product of an air compressor. Yes, you can put a larger air filter on, quiets the compressor down a lot, too. If you EVER plan on painting with that compressor, don't get near it with wd40!!! It'll stay in the tank and lines forever!!!! You could get a "sneezer" for the bottom, it discharges a bit of air everytime the compressor shuts off. Helps keep the moisture out. In humid weather, I crack the bleeder and get rid of the water sometimes 3 or 4 times a day.....

The easiest way to get rid of water is to use an automatic drain.

----> http://www.harborfreight.com/cpi/cta...emnumber=42221

Pat

More info.

Air Compressor Automatic Drain Valve

Copyright © 2001, 2002 by Jim Wilson
(Click images to enlarge)



I got tired of crawling under my compressor and struggling with the sticky drain valve to clear the accumulated moisture from the tank every morning, so I when I stopped in at Harbor Freight one day, I picked up one of their automatic drain kits (a.k.a. "Auto Compressor Drainer Kit"). Ten bucks, how can I lose?

The automatic drain valve replaces the manual drain valve on the bottom of the tank. It needs more space than the manual valve, and you may have to raise the tank to accommodate it. Mine sits on a couple of 4x4 blocks.

The auto drainer is pressure actuated. It ejects tank condensation through a 1/4" NPT opening in the side of the valve each time air pressure is applied or removed from the small fitting on the end of it. You can see the hole in the picture of the kit.

Installation was pretty simple, but I did run into a couple snags.

The instructions say the valve actuator is supposed to be connected via a plastic tube to either the "discharge line unloader" or the "combination tank check valve and discharge line unloader." Alternatively, the valve actuator line can be "tee'd" in line with the "vented pressure switch", the "pilot valve," or the "receiver pressure unloader."

What??? I took a closer look at my compressor and its manual.

It's a 6.5 HP (yeah, right) Craftsman Professional model with a 60-gallon tank. I also spent a few minutes surfing the web for some help with the terminology. Turns out that a "receiver" is a compressed gas storage tank. The tank! Makes sense, I suppose, but I never would have guessed it.

An unloader is a valve that releases pressure. I was briefly confused by a few places on the net that also used that term for the Safety Relief Valve, the normally closed valve that opens if the pressure in the tank exceeds the valve rating. My safety relief valve is located on the manifold at the top of the tank, right under the pressure gauge. It has a little key ring on it, which you can pull to test it. But this is not the "unloader" that the directions are talking about.

When the pressure switch shuts off the compressor, it also activates a valve (the unloader) that relieves the pressure over the compressor piston, so that when the compressor restarts, there is no pressure on the piston. This permits an easier start, and an easier start means extended motor life. On my system, there is a line running from the compressor to a check valve mounted in the top of the tank.
Coming out of the side of the check valve is a small aluminum tube that runs to the pressure switch. That's the unloader line. Learn something every day.


I unplugged the compressor, released all the pressure, and removed the existing drain valve. Most places call it a drain cock, but sometimes, for reasons unknown, it is referred to as a "petcock." In its place, I installed a tee fitting with the new drain cock on the bottom (in case the auto drainer ever fails), and the auto drainer coming out of the side.

The water exit hole on the side of the auto drain valve is aimed straight down, so you can't see it very well. If you look carefully at the enlarged image, you can just make out the edge of it on the bottom of the valve.

I was a little reluctant to cut into the aluminum unloader line, but there was no other place on my system that applied and released pressure every time the compressor cycled on and off -- not that I knew of, anyway. The tee fitting that came in the kit was for plastic tubing only, so I had to run out to the Borg -- Home Depot, that is -- to pick up a standard 1/4" compression tee fitting.

I removed the unloader line,
cut a one inch chunk out of it,
inserted the tee,
and reinstalled it on the compressor.

Then I ran the plastic tube from the auto drain valve up to the tee fitting on the unloader line, plugged in the compressor, and turned it on. Argh! The new drain cock leaked -- of course! Harbor Freight, clear across town, is going to get away with it this time. :-\

After fiddling with it, overtightening it, wearing out my fingertips, and using some rare language, I gave up, trucked back over to the Borg, and shelled out four bucks for a good one. What a difference! This one has a nice knurled knob that turns easily. The valve opens and closes positively with only light finger pressure. It's a good thing I didn't have one of these before, or this page might never have been born.

Finally, success! No leaks. The automatic drain gives a satisfying "pfft" whenever the compressor cycles on or off. The spiders can live down there in peace now...

In this setup the condensation is directed straight onto the floor. Well, it would if there were ever enough moisture.

My compressor gets fairly frequent use, and sometimes cycles several times a day. The automatic valve releases a puff every time the compressor motor starts and also when it stops. So, now, rather than getting drained once a day (or less), it now gets cleared four to eight times a day. Before I installed the kit, I'd get maybe an ounce of water when I drained it, usually much less.

Now, with the moisture being cleared twice every time the compressor cycles, the amount of water is never even enough to make a wet spot on the concrete below. Of course, I live in the Arizona desert -- it's not humid here very often. If you live in a wetter climate, you could install a 1/4" NPT to barb fitting and run a hose to wherever you want the water to go.

Additional Notes:
tip from Josh Kloepping: I 'teed' into the line at the end of the unloader line closest to the compressor discharge. Unfortunately, that side gets really hot, so the hose softened and blew out. Changing to the other, cooler end fixed the problem.

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I leave mine cracked just a bit like a small leak . The moisture drains its self. I dont leave my compressor on though since i only use it part time . I close it when its sitting along time to eliminate long fill runs .

Here in Florida with our high humidity, we get lots of water in ours. What we should be doing, but forget to do, is drain the tank before each session. We do have a water seperating filter/regulator, and about 4 water traps built into the galvanized pipe system so that we can crack those open every once in a while and drain what has gotten past the filter.

I like the idea of the automatic drain the guys are talking about. Didn't know they existed.


Don

HemiT it looks like I am going to make my 3rd trip back to Harbor Freight this week. Thanks, some thing like that should help out a lot.

Yes I am getting one two
Ron

I use an automatic drain electric with a timer for how often and for what length of time there is a drain I set mine for every 45min for 20sec drain to the outside the garage. Ed ke6bn not cheap though.

Originally Posted by Ed Rodder

I use an automatic drain electric with a timer for how often and for what length of time there is a drain I set mine for every 45min for 20sec drain to the outside the garage. Ed ke6bn not cheap though.

Ed, who makes that and where are they available from? Sounds like a good plan for us semi-senile types who don't always find the drain valve in a timely fashion!!!!!

Originally Posted by Dave Severson

Ed, who makes that and where are they available from? Sounds like a good plan for us semi-senile types who don't always find the drain valve in a timely fashion!!!!!

The unit I have when I checked the data plate is called Electronic Timer
type ET 20m
1-45 min delay
0-15 sec. on time for bleed.
also has a manual mometary bypass to bleed

The name on the side where purchased is Benz Engineering 800 6984247

I Think there are cheaper units and maybe even Harbor Freight has an electronic one something like this.. This has been in service several years with out a glitch. I tried many of the auto one that react to pressure drop etc. and all plugged and failed for me. In the long run probalby worth the money spent.