View Full Version : Water condensation.

03-17-2011, 02:51 AM
I am concerned about water in high pressure fill tank (4500#). I don't want to ruin my expensive air guns. Please advize on water traps and air drier equipment needed to safely use my Shoebox compressor. There has been extensive decussions on water condensation going to high pressure on the yellow airgun forum. Any thoughts on this would be appreicated. I am expecting my Shoebox this Friday. 30 -40% humidity in my area.


03-17-2011, 04:20 AM

I have been following the discussion on the Yellow. I don't know what more I could add. The desiccant filters that turn blue seem to be the best idea since you can get a feel for how much water they are trapping out. If your really worried about it you will have to spring for the scuba type high pressure down stream filters. Most guys are not having a big problem so it depends on what level of "dry" you want.


03-17-2011, 10:32 PM
I am wanting dry enough air to not cause damage to my airgun. You can read both fact as well as fiction on forums. I just wanted a qualified answer to how to get dry enough air as to not cause damage to my airguns. In your opinion should I spring for the scuba type high pressure down stream filters or how large of a desicant filter would you suggest and how to apply.

03-18-2011, 03:30 AM

I can't really give you a qualified answer because in 20 years of building, designing and powering air operated guns I have never seen one damaged by water. Granted these are all paintball guns, but I am pretty sure the internals work the same. In air rifles virtually none of the guys using hand pumps filter out the water and they seem to do ok. I can understand that you have a large investment there so your basically buying "insurance" that they will be fine in the future. The only way that I am aware of removing all the moisture is to use a downstream trap at full pressure like the scuba guys do. If it was me, I would price how much it costs to replace the pressure tube in my guns and weigh that against protecting them.


03-18-2011, 04:38 AM
I thank you for explaining this to me I have been in the shooting sports for many years. However in firearms (powder burners). This makes sense. Never considered hand pump use. I have spent a large amount of money (to me) on airpowered guns DAQ 308, FX Royale and a Daystate Air Wolf, and was concerned about the forum discussions. I would have called you on a phone had I access to a number. Probably the older hands at this game never even considered this a problem.
Thanks again,


04-25-2011, 01:36 PM
Tom do you think the cooling fan aimed at the shoebox reduces the condensation? It would seem keeping the entire thing running cooler would be a huge help with condensation from the air cooling. I run a $10 walmart fan on my compressor hooked up to a power strip so when the compressor is on the fan is on period. I can hold my hand on the cylinders after a couple hours running.

04-25-2011, 04:38 PM
Yes the fan and anything the cools the air should help condense out moisture. At some point I will have to do an actual test and see how much moisture is left in the tank.


04-29-2011, 05:01 PM
I would be interested in someone checking a tank that has been filled alot. I know when you get a scuba tank the air is so dry you want to drink the salt water after being under it for 20 minutes or so! lol
I cannot imagine airguns would be so sensitive that a small amount of moisture would destroy them? Any filter system will help I guess.

05-09-2012, 05:14 AM
First time running the SB I didn't have a water dessicant/filter/seperator.... I'm in south Louisiana, and I don't recommend it. Releasing pressure from the 1' fill hose on my tank let out about ten drops worth of water.

05-10-2012, 10:57 PM
I added a fan to cool my Shoebox cylinders and put an inline McMaster-Carr desiccant filter because it allows the desiccant to be removed, dried, and reused. I also added an inline pressure gauge although it isn't essential. I added it for a very small additional cost from Harbor Freight. It allows me to check the fill from time to time and know that the input pressure is holding steady.


06-01-2012, 07:00 PM
Hi Everyone;

New member, awaiting the 2X speed "full cooling package" to come out before he buys.

Are we discussing condensation outside the system or inside?

I would have thought the compressor would run warmer than ambient and no external condensation would accumulate. Thus, I will address the internal component. If I am incorrect, please forgive me now.

Cooling the compressor will not stop condensation trapped INSIDE the system. The system is sealed and there is no place for the water to go.

The condensation inside the system is the humidity in the air and the greatest possible water component at 30C is approximately 30 grams per cubic meter. (http://en.wikipedia.org/wiki/Humidity#Absolute_humidity) Most folks will fill at cooler temps (less water) and lower humidity (less water again). Because this is truly a worst case scenario I'll use this for my discussion.

I did a little math. 30ml of water/cubic meter. 34 cubic feet per cubic meter. This is ~0.87ml per cubic foot at 100% humidity at 30C.

I assume my 88 cu inch tank holds 88 cubic inches of air at 1 bar. If I understood this correctly, then my 87cu-inch (0.05 cu ft) tank at 30bar would have 1.3ml water if I filled from zero at 30C in 100% humidity. I fill using room temperature air in a semi-desert so my water component of the fill will be far less. Even the folks in Hawaii, Miami, New Orleans or Brownsville will do way better in an air conditioned room.

A similar fill from 3000 to 4500 (20 to 30bar) would add 0.4ish ml per each additional fill at these conditions.

Perhaps one could purge a quick puff of air/water from an inverted and completely cooled tank?? Visualize shooting a single shot straight down, or up, if that orients your tank mouth down, then all condensed water will blow out of the tank on this shot, all subsequent shots will dry the gun with the explosive force of dry air.

Another way to see it. Divide your total calculated water by the number of shots taken. No matter what any tiny bit of condensed water will return to the air as humidity soon after release from the tank. Me? I am not going to even consider this issue. I live in SoCal. I don't have any water issues. I'd love to hear from guys in wetter climates.

While the totality of this discussion is real and I believe my math to be correct, please forgive me if I misunderstood the problem being discussed.

Scott Solar

06-01-2012, 09:12 PM

I believe your numbers are correct but don't forget a lot of water is taken out in the shop compressor tank. Most of the water stays there instead of going on to the ShoeBox.


06-01-2012, 11:44 PM
Good point! I think based on this the water issue is non-existent.

In my case, my compressor has a 60 gallon verticle tank. I can fill it up a day ahead, let it cool overnight, drain the condensate from the tank. This will leave very dry air for the shoebox to make it's fills from.

Thanks to you TomKaye for making life just a little bit better.

Scott Solar

Ron S
02-19-2013, 10:40 AM
You are right,concerning the water in the tank! Just "invert" the tank,and crack the valve to give it a little "burp"! If any water is present,it will be expelled in the shot of air. Draining the "first stage" compressor (shop compressor) will do more to clear water out of the system,than all the filters you can install.

04-29-2013, 02:42 PM

Do you know where I can find a high pressure filter for the output side? I would like to price them to see what the cost is. Thanks.

04-29-2013, 04:31 PM
Joe Brancato at AirTanksForSale.com is developing one now so you can ask him.


Case Stuffer
07-05-2015, 02:21 PM
I know this is a very old thread but it seems to me this question / issue is still very current these days.

See post #11 here

and post #12 and explain to me why this is even a remote concern.

Yes I have read post on air gun forums of oxidation and rust (rust is in fact oxidation) in the guns air camber hich is not good but where did it truly come from?

FWIW I add two very small drops (from a needle tip) of RWS silicon air chamber oil to the foster fitting on airgun every 3 to 5 hand pump fill ups and I pump pump very slow and deliberate and take a couple of short breaks airing Disco from 1K to 2K which is 55 strokes and the first five are just to get pump and line to 1K.

Added: Now that newer Shoebox MAx and Freedom 8 use continues silicon oil lubication it would seem to me that the output air will have a very fine silicon oil mist in it and this should be beneficial to the air gun, not harmful.

Added: Found this post



We use grease so its heavy and does not readily atomize but you must always be careful because its not a perfect world.


So I guess I just overthinking this but grease gets very thin when heated and now silicon oil is being used to lube the cylinders. I know things change and most often threads / post do not get updated and many post here are 3 to 5 years old.

Case Stuffer
07-12-2015, 09:38 PM
The Silicon oil supplied with Shoebox is a 1000 cps according to Tom and info on the web says it has a flash point of 300 C which is 592 F..
Any experts around with any opinions as to the possible harmful effects of any resulting lubrication mist from the SB to an aluminum air tank (inner part of a CF tank) ?

TKO AIRGUNS suggest that a few drops of Silicon oil in the fill fitting of a PCP will help prevent oxidation and rust.


Scroll down to hand holding fill adapter and seal.

I have been adding a couple of very small drops of RWS Silicon air chamber oil to my Disco's Foster fitting ever few fills from the very beginning but it is still very new so only time will tell how it does over the months and years ahead.