Do you drain your air compressor tank?

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Nov 29, 2009
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I bought a new Quincy compressor and I would crack the water drain valve open for a few seconds every few days thinking that was enough to get the water out. Then I discovered I can go back 30 minutes later and get more water out each time without the pump still not turned on. I wonder if I need to just drain the tank completly after every use. Although an empty air compressor imo doesn't do much good. Imo constantly draining the water will rust the tank faster because rust only occurs where their is air. If that one area of the tank always has a little bit of water at the bottom it won't rust as much imo.
 
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mine has been in the garage attic for 15 years ,no rust, synth oil as per this board and never drained.
 
Not as often as I should. When I do drain (every couple weeks?) the water comes out brown so evidently there is some rusting going on. It's not a high dollar compressor by any means so if the tank goes someday, I'll just replace it. Will probably take a long long time for a tank to rust through.
 
Thanks for the reminder!
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Yes, you should drain your tank. A compressor service tech told me about a local car dealer shop that was saying their compressor wasn't working right. Turned out that the 80 gallon tank was completely full of water! I always drain mine when before I fire it up while the compressor is cool. Otherwise water in the tank will vaporize when the hot air hit's it and send it down the air line. You could always install an automatic tank drain, which is basically just a solenoid valve operated by a timer. When it's warm and humid is when the water builds up pretty fast in a compressor.
 
I installed a ball valve on my compressor. I usually open the drain for 5-10 seconds once or twice a week and let the water drain out. Every month or so, I'll let all the air out of the tank and then I'll fire it up and let it run until it's full (60 gallon tank).

Originally Posted by honeeagle
mine has been in the garage attic for 15 years ,no rust, synth oil as per this board and never drained.


Are you sure about that? All compressor air tanks will get water inside them due to condensation.

When I bought a 27 gallon coleman compressor a few years back, the first thing I did when I got home was drain the tank. There was at least 1 liter of rusty water inside that tank. The previous owner never drained it. It was so rusty it looked like gravy. I installed a ball valve on it and draining it was easier.
 
If you leave a puddle of water in the bottom of the tank, and if (big if) it doesn't corrode "underwater", it still will at the "shoreline".

I usually drain mine, and leave it open, but don't put tons of thought into it.
 
I don't drain mine unless I'm using it. Being that I'm a semi mechanic, I put a manual drain valve with a lanyard on my air compressor which makes it a breeze.
We had a smaller Quincy back up compressor fail the annual tank sonic test and tossed it in the scrape bin at work. Ran fine, but no one wanted it with a bad tank.
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Pretty frequently, mines an 80 gallon vertical. I plumbed the drain out to be easily accessible and used a ball valve with a male air coupler to fill my portable tank.
Of course I purge it before filling the storage tank.
 
Originally Posted by motor_oil_madman
I wonder if I need to just drain the tank completly after every use.


That depends on several things.

What is the tank construction? ( almost all are ASME certified for pressure but the plate thickness has more to do with how much corrosion it can withstand)

Do you need instrument quality air?

Business or home use?

Coded or non coded system?

The average home use system will be just fine with even a monthly drain ( unless you have high humidity and really use it a lot)

Weekly is better, every use is even better- a timed drain is the easiest over the long run.

Lot of choices there and all of them will work and have limitations- depends really on your usage rate and how clean you need the air.

I need almost hospital grade clean dry air because of instruments and tooling but the average mechanic use can get by satisfactorily with nothing more than an "every once in a while" schedule. (and a good separator in the line)

Lots of ways to do this and the system
 
If pumping hot air directly into tank water condensat will be much greater than if it was equipped with a after cooler and separator. You seem to be obsessed over a bit of water in tank during and after use. To be honest drain tank before and after if used for intermediate daily use. For 100% duty cycle use example Sandblasting I may have 1hr long pump run times or more just keep valve cracked during use.

You have a high end build unit with a high quality tank using common sense and little maintenance it will last a lifetime.
 
Every tank I've had had a petcock on the bottom so it was always easy. I leave the petcock open when not in use as I feel if the petcock is closed there's no air movement thus rust will develop. When I turn it off and I'm done for good, I crack it so if there is any moisture it will blow out besides the air going past will dry any water out.

However, I think the inside of the tank is unpainted metal and will rust regardless. By draining, we are not accelerating the decline.
 
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I also have a Quincy. I drain it until the water stops when I remember, so every so often. I will drain it completely maybe once a year.
 
I added a ball valve to mine.

Open it every time I shut off the compressor, if I'm using it infrequently.

If I'm running the compressor daily, then I drain the water daily.

20 year old Craftsman compressor - homeowner type - still works great.
 
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I don't like blowing moisture into my tires when I air them up . Possible damage to the tire pressure monitors ? I don't know but that's my theory anyway .
 
Originally Posted by nomas
I don't like blowing moisture into my tires when I air them up . Possible damage to the tire pressure monitors ? I don't know but that's my theory anyway .


I like to pick low dew-point days to mount and inflate my tires!
 
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