Replacing compressor Drain

[Ken Krawford]

The drain valve on my PC 6 gallon compressor needs replacement and I've never liked the one that came with it. Lowes sells a 1/4 turn ball valve with a 1/4" stem. I'm a bit reluctant to start horsing on the old one because I can't see any threads protruding outside the tank. Is this stem welded or is the paint obscuring any threads?

398452

[John K Jordan]

The drain valve on my PC 6 gallon compressor needs replacement and I've never liked the one that came with it. Lowes sells a 1/4 turn ball valve with a 1/4" stem. I'm a bit reluctant to start horsing on the old one because I can't see any threads protruding outside the tank. Is this stem welded or is the paint obscuring any threads?

398452

By stem do you mean the hex nut? I don't know about yours but at least one of my compressors has a welded boss threaded for an fitting with visible threads and with a hex head, intended I think only to reduce the opening to fit a standard brass tank drain valve. You might use a wire brush on a drill to remove the paint and have a better look. But I'm not sure why the fitting would need to be replaced unless it was badly corroded (then I might be concerned about the rest of the tank.)

One thing that helps is to put the valve on the end of a piece of pipe that sticks out a bit from the bottom of the tank.

[Jim Becker]

Most compressors have 1/4" NPT threading for the drain so it's easy to replace with simple 1/4" NPT fittings and a ball valve for easy draining. The OEM drains are a pain in the backside right from the start in that respect and are also not generally "conveniently located".

[Kerry Wright]

I replaced mine last summer with a street elbow (1/4" NPT), a 4" nipple and a ball valve. Much easier to reach to drain now!

[Ken Krawford]

Problem solved. I put a wrench on it and a couple of whacks with a mallet separated the threaded portion. The pain was concealing the junction between the 2 pieces.
Thanks for the responses.

[Brice Rogers]

I have a multi-turn drain valve. I set it at the "almost closed" point about 20 years ago. It takes perhaps 3 days to 5 days to drain down the tank. My rationale for doing this is that it automatically empties the water from the bottom of the tank. When I'm out of town, I try to remember to turn off the tank so that it doesn't cycle unnecessarily.

[Tom M King]

I changed all mine to ball valves. I admit to having one that has a nipple held in with JB Weld. It's a really old one mounted up high in the trailer shed. That one gets used so rarely, only for topping off tires, or running an air wrench occasionally that I had just neglected it for too many decades. I decided to change all the others after that one, that was too much trouble to get to with a TIG welder.

[Bruce Page]

Ken, add an automatic drain valve and never mess with it again.
https://sawmillcreek.org/showthread.php?17659-Finally-some-air!

[Charles Lent]

I've gone through 3 automatic drain valves on my 80 gal IR compressor tank and each failed in a very short time, usually only a couple of months. I now just have an accumulator made from two 1/4 - 2" pipe adapters and a 1' long piece of 2" pipe. It's output has a 1/4" ball valve and more pipe to vent it out through the wall of my compressor shed. Whenever I think of it I open the ball valve for a few seconds and the condensate is blown outside. As long as I do this every month or so, no condensate ever builds up in the compressor tank. I just need to remember to only do it when my neighbors aren't outside, because the sudden roar is quite startling.

Charley

[Mike Cutler]

The drain valve on my PC 6 gallon compressor needs replacement and I've never liked the one that came with it. Lowes sells a 1/4 turn ball valve with a 1/4" stem. I'm a bit reluctant to start horsing on the old one because I can't see any threads protruding outside the tank. Is this stem welded or is the paint obscuring any threads?

398452

Ken
If it's like mine, that is welded boss on the tank. I put a drain valve in mine also. I no longer use it as a compressor, but as a secondary air receiver tank. The compressor died a few years back.
An auto drain will not work for you on this tank. The drain is above the bottom of the tank, so you won't get the moisture out of the bottom of the tank effectively. I always had to tip mine to put the valve at the lowest point. It's also way too small to realize the benefit of an auto drain.

[Jim Becker]

I've gone through 3 automatic drain valves on my 80 gal IR compressor tank and each failed in a very short time, usually only a couple of months.

I picked up an IR auto drain "for a song" off EBAY years ago and it's not failed yet.

[ChrisA Edwards]

I have to admit, I'd never drained my tank for several years and finally did it prior to getting ready to do some automotive type spraying.

I bled the air out of the tank and then loosened the drain valve. I expected quite a large amount of water to come out, so I moved my compressor to the edge of my garage, but all I got was about 6 drops (little brown stain) of water that didn't even flow out.

Naturally, after loosening the drain, it refused to seal again, so it leaked a little air until I could replace it.

https://i1094.photobucket.com/albums/i452/cedwards874/Bike%20Stuff/CompressorDrain.jpg

[Charles Lent]

Drain it again when the tank has pressure in it. You will be amazed what comes out. The tank needs some pressure in it to blow the water out. That nasty rusty water from your tank says that the water has been in there a long time and has been heavily rusting the inside of the tank and decreasing it's life. You would be amazed how thin these tanks are, and it doesn't take much rusting to significantly weaken them. It's also amazing how much damage can be caused when one of the little pancake compressor tanks explodes. I can't even imagine an 80 gallon thank exploding. It would flatten the shop and quite likely kill anyone in it.

Charley

https://www.google.com/search?q=photo+air+compressor+tank+explosion&rlz=1C1CHBF_enUS814US814&tbm=isch&source=iu&ictx=1&fir=bdEVzxBwKWJADM%253A%252CjmP4g2xAFQIOoM%252C_&usg=AI4_-kS6HNYmh5ftkHOx3CJg9vAr4zwTGw&sa=X&ved=2ahUKEwiG3ZyXo5jfAhVMeKwKHWtdA2sQ9QEwC3oECAQQC g#imgrc=dobph1RLDqrE4M:

https://www.google.com/search?q=photo+air+compressor+tank+explosion&rlz=1C1CHBF_enUS814US814&tbm=isch&source=iu&ictx=1&fir=bdEVzxBwKWJADM%253A%252CjmP4g2xAFQIOoM%252C_&usg=AI4_-kS6HNYmh5ftkHOx3CJg9vAr4zwTGw&sa=X&ved=2ahUKEwiG3ZyXo5jfAhVMeKwKHWtdA2sQ9QEwC3oECAQQC g#imgrc=bdEVzxBwKWJADM:

[ChrisA Edwards]

Drain it again when the tank has pressure in it.
Charley


Wise words indeed, but realistically, and this is a question, how do you stop this rusting process? Moisture will get in as soon as the compressor runs.

I am going to replace the drain valve with an easier to get to method, as described earlier in this thread.

[Bruce Page]

I've gone through 3 automatic drain valves on my 80 gal IR compressor tank and each failed in a very short time, usually only a couple of months. I now just have an accumulator made from two 1/4 - 2" pipe adapters and a 1' long piece of 2" pipe. It's output has a 1/4" ball valve and more pipe to vent it out through the wall of my compressor shed. Whenever I think of it I open the ball valve for a few seconds and the condensate is blown outside. As long as I do this every month or so, no condensate ever builds up in the compressor tank. I just need to remember to only do it when my neighbors aren't outside, because the sudden roar is quite startling.

Charley

I installed the IR ADV in 3/2005 and it's still functioning as new. I wired an on/off switch and power it up only when I'm using air. I do not leave it powered on 24/7.

[John K Jordan]

Wise words indeed, but realistically, and this is a question, how do you stop this rusting process?...

Buy a stainless steel tank? I've never seen a compressor with one, though.

JKJ

[Mike Cutler]

Wise words indeed, but realistically, and this is a question, how do you stop this rusting process? Moisture will get in as soon as the compressor runs.

I am going to replace the drain valve with an easier to get to method, as described earlier in this thread.


You don't unless you want to spend some big$$$$ for a lined tank, or a stainless steel tank. You prolong the life of the tank by periodically draining off the accumulated moisture.
The air receiver's job is twofold; Capacity volume for the system, and the first stage of mechanical moisture separation. If your system is sized properly the air receiver will remove the bulk of the moisture from the system. Secondary air receiver tanks, coalescing filter traps, desiccant cartridge filters, coolers and dryers, do the rest.
Your tank s supposed to condense the moisture in the air.

[Ed Edwards]

I read this and the related previous threads. For the life of me, I can't understand why anyone wouldn't exhaust the condensate when you're finished with the compressor, or at the end of the day. Routinely draining it at least once a month is certainly inviting disaster...

Ed

[Tom M King]

I recently repaired a leaking fuel tank on one of the tractors. One of the products I used was a thin epoxy for coating the whole interior of the tank. The first step is to take the inside of the tank down to bare metal with Muriatic acid. If I ever buy a new compressor, I'll strongly consider doing this to the inside of the tank. The new, lined surface is slick, hard, and I doubt it will ever rust again.

After rinsing the acid out with water, I heated it over an outside cooker burner, on very low heat, until it was completely dry before pouring in the lining.

Here's the product. It goes a lot farther than it seems like it would. I bought extra cans, but one was easily enough for the 20 gallon tank.
https://www.amazon.com/gp/product/B00B3I2NWG/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1

[Bill Dufour]

I think a coating of motor oil spread all over the tank might stop rust? It will not be carried into the airstream to harm finishes. Of course water sinks below oil so it may no really help at the bottom.
I do have two surplus stainless oxygen tanks but that supply is gone after 80 years. I understand new planes use liquid oxygen so no pressure tanks are flown anymore.
Bil lD.

[Mike Cutler]

I read this and the related previous threads. For the life of me, I can't understand why anyone wouldn't exhaust the condensate when you're finished with the compressor, or at the end of the day. Routinely draining it at least once a month is certainly inviting disaster...

Ed

Ed
You won't get it out that way either, unless you have a fairly large orifice in the bottom of the tank.


Given time, and it doesn't take that long, a static receiver tank can be rid of the accumulated moisture. Once this is done there is no reason to exhaust the entire receiver tank, and there is a very good reason to leave that receiver tank full of air when not in use.
Once the receiver tank has performed it's function, mechanically separating moisture from the compressed gas, the moisture content inside the tank is now reflective of the ambient air temperature and the pressure inside the receiver tank. If both stay static, then no more moisture is coming out of the compressed gas, but temperature is going to be a dynamic variable and as it lowers, during the night, more moisture will condense. Being that the receiver tank is an enclosed volume, as the temps increase during the day, no more moisture can accumulate. If you have an auto drain you will remove all available moisture from that tank in a few days. Once a month is a little bit long of an interval, especially if the compressor is being used during the interval.
You want the air in the receiver tank to be as low in moisture content as possible. If you were to exhaust the entire tank after each use, and then fill the tank just prior to use, all of the air inside of that tank is in a saturated moisture condition. This air has moisture now, in the form of vapor, which is going to move through the system very quickly. Even the best desiccant filters cannot keep up, and you will have moisture coming out at the end of the line, and into tools and spray guns. Sometimes enough that you can actually see it.
Once the entire system is saturated no amount of filtering, or refrigerating, is going to remove this moisture until the system is at stasis, and then they can begin to remove the moisture.
In the case of the OP's compressor, that is is a very small pancake type compressor with a 6 gallon receiver tank. It could be left pressurized in between uses and the moisture removes, by tipping it on it's side, putting the drain valve at the bottom, and blowing it down. But generally they're just turned on prior to use and the tank comes up to pressure. Since their intended usage is pneumatic nailers, the moisture isn't a big deal. I have/had this same compressor for many years. My small portable is a Rolair JC10 now. The old 6 gallon tank is a secondary air receiver tank in my system.
If you have a large stationary air compressor, the receiver tank should be kept pressurized at all times to allow it to perform it's primary function of moisture removal.

[ChrisA Edwards]

If you have a large stationary air compressor, the receiver tank should be kept pressurized at all times to allow it to perform it's primary function of moisture removal.

You have way more knowledge of this whole process than myself, so as my compressor was kept pressurized for about 3+years before I decided to drain it, is that why I saw such a little amount of water come out when I finally did drain it?

[Kevin Beitz]

I think the reason we don't see stainless steel tanks is that stainless does not take stress well at all. The continuous expansion of the tank would make fatigue cracks in the metal.

[Mike Cutler]

You have way more knowledge of this whole process than myself, so as my compressor was kept pressurized for about 3+years before I decided to drain it, is that why I saw such a little amount of water come out when I finally did drain it?

Chris
It could be.
I would have expected more moisture than that to accumulate after three years, but ????.
The color of that fluid would bother me though.

I've been maintaining large industrial air systems for most of my working life, in a nuclear power plant. Primarily the process control part of the systems, but I've done a few overhauls also. The hard part for me is scaling it down to a small workshop, or garage shop. All of the system parts work the same though, it's just the size of some of them that is different.

[Ed Edwards]

Mike
Thanks for the enlightenment. You contributed a wealth of info that I was totality unaware of.

Thanks, Ed

[Curt Harms]

I read this and the related previous threads. For the life of me, I can't understand why anyone wouldn't exhaust the condensate when you're finished with the compressor, or at the end of the day. Routinely draining it at least once a month is certainly inviting disaster...

Ed

To me that's one of the advantages of extending the drain with pipe. Assuming the drain is at the lowest part of the tank, any water should sit in the pipe, not in the bottom of the tank. I don't use a compressor much, if it runs 15 minutes a month it's been a busy month but have never gotten more than a few drops of water out of it.