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Compressor filters, do they really work?

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I think that looks great as is. My only advice is that you isolate the Omega media filter from the coalescing filter and the ambient air when you are not using the compressor - this will help the media last a lot longer. If you don't it will pull water vapor out of the airstream, which is a waste of its capabilities.
The easiest way to co that would be by connecting the input and output ends with a hose that closes the loop on it. Hopefully your output line would work for this as is, simply by connecting it to the filter's input . . . .
 
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Alan, a word of caution relative to coalescing filters. In the Target Forge video where he tested different filters on a GX CS2 and on a Yong Heng, he found the coalescing filter did nothing - no benefit at all - for the CS2. He states that he thinks it was the low flow rate of the CS2 and that he found a paper that states the coalescing filter is sensitive to flow rate. So when we add one to our systems with no ability to change the filter size or the flow rate, it may or may not work. He uses one on his Yong Heng, however. He did not test the result on the YH. I believe the GX CS4 has this type of filter.

I use a "tampon filter" first which I see you recommend to get water. It also gets oil from my YH. I agree a coalescing filter might do the same or better but I have used the stock YH filter first for a couple years now with good results.

Given the low price of the tampon style filters I think they are great for a first stage. I change the element after each tank fill (I bought a bag of 100 cheaply from Aliexpress). But I would also consider raising the filters in the pictured system to cause water that condenses in the line to flow back to the compressor where you can vent it. I vent very five minutes of run time and it is obvious water comes out.

I don't do anything special to keep my dessicant dry between runs (once a month typically with the dessicant getting used for several runs) but I have a one way valve in the output of the filter the dessicant is in. The other end of the line is connected to the YH. I think there is a one way there too but I've never checked it. I have a spare cartridge but the dessicant in it changed in less than a month even though it was in a zip lock bag. So the bag leaked more than the valves on the compressor line.
 
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JimD said:
Alan, a word of caution relative to coalescing filters. In the Target Forge video where he tested different filters on a GX CS2 and on a Yong Heng, he found the coalescing filter did nothing - no benefit at all - for the CS2. He states that he thinks it was the low flow rate of the CS2 and that he found a paper that states the coalescing filter is sensitive to flow rate. So when we add one to our systems with no ability to change the filter size or the flow rate, it may or may not work. He uses one on his Yong Heng, however. He did not test the result on the YH. I believe the GX CS4 has this type of filter.

I use a "tampon filter" first which I see you recommend to get water. It also gets oil from my YH. I agree a coalescing filter might do the same or better but I have used the stock YH filter first for a couple years now with good results.

Given the low price of the tampon style filters I think they are great for a first stage. I change the element after each tank fill (I bought a bag of 100 cheaply from Aliexpress). But I would also consider raising the filters in the pictured system to cause water that condenses in the line to flow back to the compressor where you can vent it. I vent very five minutes of run time and it is obvious water comes out.

I don't do anything special to keep my dessicant dry between runs (once a month typically with the dessicant getting used for several runs) but I have a one way valve in the output of the filter the dessicant is in. The other end of the line is connected to the YH. I think there is a one way there too but I've never checked it. I have a spare cartridge but the dessicant in it changed in less than a month even though it was in a zip lock bag. So the bag leaked more than the valves on the compressor line.
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Jim,

Those are good points. A coalescing filter does require flow to work as designed. I do think chilling them is a good idea, but that could also be done with a "tampon filter" too.

I fill with a Shoebox compressor, so I have a huge Wilkerson desiccant filter on the input side, but like you I also use a media filter on the output side to catch oil, as I prefer to keep that out of my fill line. It is one of the tiny ones, with the cigarette sized filter, but it is all I need as it has never seen a drop of water.

Glad to here your media stays dry with no added action on your part. That is nice!
 
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I only have a Vevor shoebox type 4500 psi unit. (funny how it says RovAir at one place in manual 🤣) So is essentially a RovAir. I use 2 of those threaded aluminum cylinder cotton element. One came with at the compressor and I have other at the gun end of the whip.
what Is Encouraging is that I Never See or feel any Dampness in the Second Cylinder filter even if I Do feel it in the 1st Filter’s element.
This would be after running for about 8-15 minutes depending on need. All said I am quite Happy with that little $275 machine after a few months of owning.
(I think RovAir is about $525 and appears to be Identical in dimensions and features… maybe they’re making too much $$ on that unit?? 🤨)
 
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The further away from the compressor (the closer to the gun), the better the filter will do it's job.
The theory behind this is that on the compressor side, the water is still steam and harder to catch by the filter media. The air starts to travel through the hose and cools down, the water turns from steam into bigger droplets = easier to catch.

What i often see is that people mount a filter straight on the compressor. That's the wrong place. It should be as close to the gun as possible.

I'm a car spraypainter and this is what i learnt keeping the paint moist free as possible.
 
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The water in the output of a high pressure compressor is not steam. In ambient air we call it humidity. I guess we can consider it humidity in high pressure air too. The oxygen in the air can carry moisture but how much moisture it can carry is a function of the pressure and temperature. Increasing pressure decreases what the air can carry. Increasing the temperature increases the amount of moisture it can contain. The compressor does both, it raises temperature as it raises pressure. But the temperature falls and when it goes below what the air can carry at it's pressure the water condenses. Absorptive and coalescing filters can remove condensed water but not moisture in the air. Dessicant filters remove moisture from air. If we chill the air on the way to the gun or tank below what it will see later, and remove the resulting water that condenses we can be successful. But with winter coming the temperature the air will see later will decrease. I think it's easier and possibly better to just use a filter with dessicant in it. As long as we use enough dessicant filtration the high pressure air will not contain enough moisture to condense even in winter time temperatures.

The steps I use are:

1) put filtration above the compressor so that water that condenses in the lines and possibly the filter drains back to the compressor where I vent it.
2) Use an absorbent filter (stock YH) next to get water that has condensed but not quickly enough to flow back to the compressor. This filter is usually at least a little wet, sometimes I can squeeze out several drops. It always shows signs of catching oil.
3) Use a filter with dessicant in it to get moisture that is still in the air. This filter is above the absorbent one so water can flow back to the absorbent one if it condenses early in the filter. This one seems to get little moisture. It takes about 6 tank fills to change color.

I fill my guns from a 45 minute SCBA tank. I've never checked inside it for moisture but I have looked inside my guns (for other reasons) and see no sign of moisture. The compressor and tank are in a room off my garage that is not heated or cooled. It is attached so that reduces the temperature swings. I sometimes take the tank with me if I will be shooting away from home more that the shots my guns hold.
 
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Ghulam said:
Every filter has some kind of cotton, foams, cahrcoal or a desiccant and these tubes supposed to filter water and oil.. when a compressor pushes air of 250 bar pressure through this tube, how a desiccant decides to hold the water under that pressure but let the air through?
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i recently took apart my air rifle to see what makes it tick. thedesign of most air rifle is just a machined ported aluminum block with "o" rings and air passages with screws, a trigger mechanism for releasing air pressure and a storage pressure reservoir. i really don't understand the fuss over filtering moisture with stuffed restrictive filters to remove moisture. i see no rust problem with the ported aluminum block, and if the screws are checked and protected with anti-rust protection then a simple water filter would remove sufficient water to prevent drowning the passages in water. the air pressure released during firing should easily expel most moisture out of the system. air rifles aren't compicated or require all that restrictive filtering system to function. most likely, if there was a moisture problem the gun designers would have made it an issue with further recommendations. i don't recall seeing any. air rifles are not delicate little rolex watch
 
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I agree they are not terribly delicate but air at 3000 to 4000 psi is not something to take casually either. The issue is the corrosion of the aluminum that can occur if moisture is in the high pressure air in contact with aluminum. Edgun blames moisture corrosion for the failure of one of their PCPs. I think we need to do reasonable things to try and keep moisture out of our guns but I don't loose sleep over it.
 
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Carbon fiber bottles are aluminum inside. The Carbon fiber reinforces the aluminum liner so it does not fail but the carbon fiber would not be air tight by itself. So moisture can still damage bottles with carbon fiber on the outside. I am unfamilar with RovAir compressors but my guess is they supply an absorbent filter. That is what I use as the first stage. I added an additional filter I got from Amazon that has a plastic inner cartridge. The plastic is important to keep the dessicant away from the aluminum outside of the filter. I took the charcoal out of the cartridge and filled it with color changing dessicant. I use that filter as the second and last stage. I have a one way valve in the output side of the dessicant filter. These two filters go uphill so water that condenses in them can flow back to the YH where I vent it. I checked the dessicant after each tank fill at first but only check it after several fills now since it doesn't come close to all changing color from a single tank fill.
 
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Thank you JimD for that information.

I would order a second filter from Amazon, but I am unsure which would actually fit. I would preferably want a second filter that just connects inline with the RovAir supplied filter for simplicity. One takeaway from this thread is that I will start keeping the bottle being filled above the compressor itself. Hopefully this will assist in keeping the moisture from continuing to the bottle and drain back to the compressor.

The RovAir is my first compressor, so I am learning a lot of essential information from you guys. Thank you!
 
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I think they will connect but you may want another hose to connect to the second filter to go to your tank (fill set). I got one from Amazon and a male to male to connect the compressor to the tank through the fill set on the tank. I fill my guns off the tank through the fill set.

I don't worry about the tank height, mine is below the filters. My logic is that if there is still moisture in the air when it comes out of the second filter then I have a problem and I should see the color changing beads saturated. That has never happened. If the air is dry coming out of the second filter, it doesn't matter if the tank is above or below the filters.
 
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before you buy a filtering system, try blowing air through the system. i bought one and tried blowing air through it and was surprised they are selling this as a solution to a moisture issue. it is very restrictive. i don't recall seeing any manufacturer recommending or giving instructions on the need for a moisture filter while filling with compressed air. if a moisture trap is necessary wouldn't one of the manufactures already have responded to this issue here on this forum??
 
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JimD said:
Carbon fiber bottles are aluminum inside. The Carbon fiber reinforces the aluminum liner so it does not fail but the carbon fiber would not be air tight by itself. So moisture can still damage bottles with carbon fiber on the outside. I am unfamilar with RovAir compressors but my guess is they supply an absorbent filter. That is what I use as the first stage. I added an additional filter I got from Amazon that has a plastic inner cartridge. The plastic is important to keep the dessicant away from the aluminum outside of the filter. I took the charcoal out of the cartridge and filled it with color changing dessicant. I use that filter as the second and last stage. I have a one way valve in the output side of the dessicant filter. These two filters go uphill so water that condenses in them can flow back to the YH where I vent it. I checked the dessicant after each tank fill at first but only check it after several fills now since it doesn't come close to all changing color from a single tank fill.
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so many solutions to a problem that doesn't exist. where exactly is the moisture problem in an air rifle? the manufactures have not mentioned anything about moisture problems. the machined aluminum block is most likely marine grade aluminum which resists rust. the screws and "o" rings are also not a problem as far as rust goes. i also don't see an accumulation of water as being an issue.
 
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sd619223 said:
so many solutions to a problem that doesn't exist. where exactly is the moisture problem in an air rifle? the manufactures have not mentioned anything about moisture problems. the machined aluminum block is most likely marine grade aluminum which resists rust. the screws and "o" rings are also not a problem as far as rust goes. i also don't see an accumulation of water as being an issue.
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Wow
 
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sd619223 said:
i recently took apart my air rifle to see what makes it tick. thedesign of most air rifle is just a machined ported aluminum block with "o" rings and air passages with screws, a trigger mechanism for releasing air pressure and a storage pressure reservoir. i really don't understand the fuss over filtering moisture with stuffed restrictive filters to remove moisture. i see no rust problem with the ported aluminum block, and if the screws are checked and protected with anti-rust protection then a simple water filter would remove sufficient water to prevent drowning the passages in water. the air pressure released during firing should easily expel most moisture out of the system. air rifles aren't compicated or require all that restrictive filtering system to function. most likely, if there was a moisture problem the gun designers would have made it an issue with further recommendations. i don't recall seeing any. air rifles are not delicate little rolex watch
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I have seen many parts, especially regulators badly corroded due to moisture. the filters wont hurt anything. moisture may also damage orings. i am reluctant to take apart pcp, it is a tedious work.
 
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All I can tell you is here, in WV, I have used two or three small aluminum filters, each with a cotton filter first and then molecular sieve beads. When I opened up three of my rifles, there was not a trace of damage. I've posted pics on here. The small filters got too tedious to fill, so I bought a large aluminum filter that takes cartridges of cotton, charcoal and molecular sieve and now use them. I'll open my guns again this winter to take a look, but I'm guessing it'll be just fine.
 
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