Does everyone really need a extra filter system on their PCP compressor?

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deadhorse

deadhorse

Member
Mar 15, 2021
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UT, United States
I live in a dry environment where the humidity can be as low as 8% and when its raining it will get up to 35%. If I only filled on dry days do I really need a extra moisture filter other then the one that comes on the hose the compressor comes with?

I would like to get a better filter than what the compressor comes with of course, but because of spending all my money on the bottle and compressor I simply cant afford a extra filter that is 100-300$. Am I really risking damaging anything to just use the one it comes with for the next couple months, probably 12 bottle fills? I have been using a Hand pump for my PCP and it hasnt had a filter on it. 

Any leads to a economical filter would be appreciated. 
 
I have a Yong Heng. After 3 years, only using the black filter (not the fancy gold filters) Air Filter 30MPA High Pressure Air Compressor Oil-Water Separator PCP Air Compressor External Bucket Filtration System Air Filter Pump - - AmazonSmile. You can get this version for about the same price with desiccant and activated charcoal, but the quantities are so small, not sure it'll do any good.

I examined my tanks recently and have no signs of water in the tanks. I also live in a dry climate where last night humidity was hovering around 12%. I believe there are a couple maintenance items you must do to keep moisture out of the tanks though. Even in this climate, condensation will happen when you compress air.

Do remember, I'm no engineer, I am not a compressor specialist, etc. This is from three years with a Yong Heng, the cheapest compressor on the market.

  1. Make sure you get a compressor with the oil and water bleed valves. Some models are strange that way. On my Yong Heng, oil bleed is on the left, water bleed on the right. You'll need to bleed both.
  2. Bleed the compressor frequently. I'll bleed every 3 to 5 minutes for a half second or a second. Amazing how much water blows out. Long ago, AEAC did a spot on compressors. He set the auto bleed for 2 seconds every 15 minutes. He lives in Florida, a tad more humid than your location. I bleed every 5 and get water every time. I could go longer, but that's just me.
  3. Bleed the oil side as well. It doesn't need to be as often, or take as long to bleed, but still need to do it from time to time.
  4. Change the filters frequently. Buy the bulk 50 packs. As soon as the lead filter begins to show oil stains, replace it. Cheap and simple. You only need change the first one (I believe 3 fit into my filter) as it catches 99% of everything. Normally, the filters in the second filter never get changed as the YH filter catches it all. Spritech PCP Air Compressor Pump Filter, 50Pcs Pump Filter Element for Air Compressor, Pump Pre Filter Sponge for Electric High Pressure 4500Psi/30Mpa Air Compressor Replacement Part - - AmazonSmile
    [/LIST=1]

    Maintenance goes a long way. Adding an activated charcoal filter to remove remaining oil fumes and desiccant beads are excellent options, but in my experience, all the extra filters are just extra seals to blow, cause slow fills and take maintenance time. Plus, the beads and charcoal need to be replaced from time to time. I have no idea how often that is.

    Having your own compressor opens a whole new world to shooting. Trips to the range are a pleasure as filling the gun takes 3 seconds and doesn't push your heart rate through the roof. I do recommend one!





 
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Lets do a little math!

8% at ambient pressure equals 80% at 150psi, thats 800% at 1500psi and were still way below airgun fill pressure!

Now do you really think you do'nt need desiccant filters!



Lets do it simple.

You have a sponge of a gallon with 1 ounce of water 1:128)

compress that 10 times (150psi) now theres 12.8 ounces of water for every gallon and at 1500psi that goes up to 128 ounces per gallon of air.

There is no way no how that a gallon of air will hold that moisture, so it will condensate in your fine airrifle and make it rust like crazy!



And yes the air volume will get way smaller as pressure goes up but water is incompressible so there is no scale up or down, it just gets worse as pressure goes up!
 
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Chickenthief - your math leaves me confused.

At 1500 PSI =800%? How can I have 800% water? Seems that I'd have one ounce of air and in my case, 87 cubic inches of water (guppy tank). Considering physical observations show that didn't happen, something seems amiss here.

Also, consider the capacity of the desiccant. The filters people are using have a capacity of maybe 10 cubic inches, and the desiccant takes 60 or 70% of that space with lots of air between the little spheres meaning there isn't a whole lot of room left for water absorption. It's gotta go somewhere, and can't take more physical space than the filter itself as water is non-compressible. To me that means the desiccant in the "Gold" filters simply don't have capacity do do much. The example below would completely overwhelm the gold filters filled to the top with desiccant beads.

In the last example, If I have a 74 cf tank, at 1500 PSI, I'd have 128 ounces (1 gallon) of water per gallon of air. A gallon of water takes 0.13 cubic feet, so my 74 cubic foot tank would have 9.9 gallons of water, and I guarantee you it's not a 10 gallon tank. Since I run at 4500 PSI, that would be about 29 gallons of water for the 74 cf tank. 

Something in that math isn't working for me.

And again, after three years of running without the desiccant and other fancy filters, I show no signs of water in the tank (dismantled when the regulatory on the guppy blew). I do use the extra "tampon" style filter for more absorption via absorbent materials, but not the desiccant beads.

Gotta help me understand this one.


 
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.....I would like to get a better filter than what the compressor comes with of course, but because of spending all my money on the bottle and compressor I simply cant afford a extra filter that is 100-300$. Am I really risking damaging anything to just use the one it comes with for the next couple months, probably 12 bottle fills?
Click to expand...

Probably not but if you end up damaging a pcp was it worth saving that $100 - $300?



Allen
 
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I have a Yong Heng. After 3 years, only using the black filter (not the fancy gold filters) Air Filter 30MPA High Pressure Air Compressor Oil-Water Separator PCP Air Compressor External Bucket Filtration System Air Filter Pump - - AmazonSmile. You can get this version for about the same price with desiccant and activated charcoal, but the quantities are so small, not sure it'll do any good.

I examined my tanks recently and have no signs of water in the tanks. I also live in a dry climate where last night humidity was hovering around 12%. I believe there are a couple maintenance items you must do to keep moisture out of the tanks though. Even in this climate, condensation will happen when you compress air.

Do remember, I'm no engineer, I am not a compressor specialist, etc. This is from three years with a Yong Heng, the cheapest compressor on the market.

  1. Make sure you get a compressor with the oil and water bleed valves. Some models are strange that way. On my Yong Heng, oil bleed is on the left, water bleed on the right. You'll need to bleed both.
  2. Bleed the compressor frequently. I'll bleed every 3 to 5 minutes for a half second or a second. Amazing how much water blows out. Long ago, AEAC did a spot on compressors. He set the auto bleed for 2 seconds every 15 minutes. He lives in Florida, a tad more humid than your location. I bleed every 5 and get water every time. I could go longer, but that's just me.
  3. Bleed the oil side as well. It doesn't need to be as often, or take as long to bleed, but still need to do it from time to time.
  4. Change the filters frequently. Buy the bulk 50 packs. As soon as the lead filter begins to show oil stains, replace it. Cheap and simple. You only need change the first one (I believe 3 fit into my filter) as it catches 99% of everything. Normally, the filters in the second filter never get changed as the YH filter catches it all. Spritech PCP Air Compressor Pump Filter, 50Pcs Pump Filter Element for Air Compressor, Pump Pre Filter Sponge for Electric High Pressure 4500Psi/30Mpa Air Compressor Replacement Part - - AmazonSmile
    [/LIST=1]

    Maintenance goes a long way. Adding an activated charcoal filter to remove remaining oil fumes and desiccant beads are excellent options, but in my experience, all the extra filters are just extra seals to blow, cause slow fills and take maintenance time. Plus, the beads and charcoal need to be replaced from time to time. I have no idea how often that is.

    Having your own compressor opens a whole new world to shooting. Trips to the range are a pleasure as filling the gun takes 3 seconds and doesn't push your heart rate through the roof. I do recommend one!






Click to expand...


  1. Thank You Saltlake58,

    Judging by your name I think we are in the same area. And I hope this compressor changes things right now it takes me an entire day to just pump my gun because of my back lol. But it is a good work out. I also got the Yong Heng with the valve on each side, thank you for clearing that up about the Oil and Water sides for me I was wondering about that. 

    May I ask what Oil do you use? That's one thing I still have to order is some oil for it and how much does it hold 1qt? My compressor is still in shipping so I haven't been able to see all the actual specs yet, should be here on the 3rd they say. 
 
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Lets do a little math!

8% at ambient pressure equals 80% at 150psi, thats 800% at 1500psi and were still way below airgun fill pressure!

Now do you really think you do'nt need desiccant filters!



Lets do it simple.

You have a sponge of a gallon with 1 ounce of water 1:128)

compress that 10 times (150psi) now theres 12.8 ounces of water for every gallon and at 1500psi that goes up to 128 ounces per gallon of air.

There is no way no how that a gallon of air will hold that moisture, so it will condensate in your fine airrifle and make it rust like crazy!



And yes the air volume will get way smaller as pressure goes up but water is incompressible so there is no scale up or down, it just gets worse as pressure goes up!
Click to expand...

Your math doesnt make sense to me either? 

And I am not saying it is wrong but maybe you can help me understand it? 

I have used air compressors for years where I am which is very dry. All sorts of tools from plasma cutters to grinders and the like.

I have never had a extra filter on them and I have never had rust issues with tools and only the tinniest amount of a short mist comes out as if it was a couple vaporized water droplets when I bleed my tanks, would a 4500psi 30cu ft. bottle be all that different then a 80 gallon 135psi compressor as far as the amount of water? 


 
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When I bought my PCP I knew I couldn't afford a compressor or tank yet so I went with the hand pump, none of the many videos or posts I read about the hand pumps and PCPS even suggested getting extra water filtration for it, where as every video "almost" I come across about a compressor pretty much says you need a 2nd "extra" filter on it.

Just wondering why it seems to be mandatory for one but never mentioned with the other when they are both doing the same job, only difference I can see is the compressor is probably pumping "hotter" air into the tank or gun vs the pump. Is it the heated air that is the difference?
 
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air-moisture-holding-capacity-imperial.1627302732.png


Part physics as the moisture capacity of air raises vs. Temperature increase.

Also why refrigerated water separators work.


 
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Healthservices - I think you also accidentally hit one of the problems in this conversation. Relative vs absolute humidity. Relative is the amount of water that air can suspend at a given temp, pressure, etc, where absolute humidity is (in the case of 10%) 1100ml water per liter of air. It seems the math above seems to be absolute while OP was talking relative. Also, forgive my metrics as I'm not proficient in metric measures, but seem simplest in this case.

I found an absolute to relative converter (It's on the Internet, so it must be accurate, right?) https://planetcalc.com/2167/

Converting 10% relative at 37C (100F) and whatever the default pressures in the calculators converts to .004% absolute humidity. So if I get my conversion math correct, that's 4ml per liter of air before compression. All this of course changes when you compress the air, but also now makes perfect sense why bleeding takes care of 99% of the water issues and whatever is left is insignificant, and may be absorbed by the normal fiber filter provided by YH. I do add a secondary filter with about 3 times the volume of the original YH filter. In my case that seems to be sufficient.

So, here's where my math starts to fall apart. - 

So, carrying out one more step, The Cubic Foot to Liter calculator says my 74 cubic foot tank is 2095 liters. (Again, it's on the internet, so I hope that's accurate). Compressing enough air to fill my entire 2095 liter carbon fiber tank to max capacity yields 8380ml 0r 8.38 liters of suspended water at 10% relative humidity. 

Bleeding over the couple hours it takes to fill the tank takes care of a loot of the water, but 8.3 liters would still overwhelm any desiccant system commonly available to the common airgunner, and my observations say this isn't the case. So, I'd say there is something wrong with the math.

Oh the joys of fluid dynamics, math, conversions between systems, and the rest.






 
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Healthservices - I think you also accidentally hit one of the problems in this conversation. Relative vs absolute humidity. Relative is the amount of water that air can suspend at a given temp, pressure, etc, where absolute humidity is (in the case of 10%) 1100ml water per liter of air. It seems the math above seems to be absolute while OP was talking relative. Also, forgive my metrics as I'm not proficient in metric measures, but seem simplest in this case.

I found an absolute to relative converter (It's on the Internet, so it must be accurate, right?) https://planetcalc.com/2167/

Converting 10% relative at 37C (100F) and whatever the default pressures in the calculators converts to .004% absolute humidity. So if I get my conversion math correct, that's 4ml per liter of air before compression. All this of course changes when you compress the air, but also now makes perfect sense why bleeding takes care of 99% of the water issues and whatever is left is insignificant, and may be absorbed by the normal fiber filter provided by YH. I do add a secondary filter with about 3 times the volume of the original YH filter. In my case that seems to be sufficient.

So, here's where my math starts to fall apart. - 

So, carrying out one more step, The Cubic Foot to Liter calculator says my 74 cubic foot tank is 2095 liters. (Again, it's on the internet, so I hope that's accurate). Compressing enough air to fill my entire 2095 liter carbon fiber tank to max capacity yields 8380ml 0r 8.38 liters of suspended water at 10% relative humidity. 

Bleeding over the couple hours it takes to fill the tank takes care of a loot of the water, but 8.3 liters would still overwhelm any desiccant system commonly available to the common airgunner, and my observations say this isn't the case. So, I'd say there is something wrong with the math.

Oh the joys of fluid dynamics, math, conversions between systems, and the rest.



If you are going to use metrics for your calculations which is much easier, it's better not to mix them with imperial imputs when constructing equasions. There are also other factors appart from reletive humidity to consider when estimating the total amount of liquid water that will result from compressing 74 cubic feet of air into a .240 cubic foot bottle. If you were to get 8.3 litres of water from compressing that much air, the water alone would take up more space than the bottle could hold. It looks like it's back to the old drawing board for you.
Click to expand...
 
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Healthservices - I think you also accidentally hit one of the problems in this conversation. Relative vs absolute humidity. Relative is the amount of water that air can suspend at a given temp, pressure, etc, where absolute humidity is (in the case of 10%) 1100ml water per liter of air. It seems the math above seems to be absolute while OP was talking relative. Also, forgive my metrics as I'm not proficient in metric measures, but seem simplest in this case.

I found an absolute to relative converter (It's on the Internet, so it must be accurate, right?) https://planetcalc.com/2167/

Converting 10% relative at 37C (100F) and whatever the default pressures in the calculators converts to .004% absolute humidity. So if I get my conversion math correct, that's 4ml per liter of air before compression. All this of course changes when you compress the air, but also now makes perfect sense why bleeding takes care of 99% of the water issues and whatever is left is insignificant, and may be absorbed by the normal fiber filter provided by YH. I do add a secondary filter with about 3 times the volume of the original YH filter. In my case that seems to be sufficient.

So, here's where my math starts to fall apart. - 

So, carrying out one more step, The Cubic Foot to Liter calculator says my 74 cubic foot tank is 2095 liters. (Again, it's on the internet, so I hope that's accurate). Compressing enough air to fill my entire 2095 liter carbon fiber tank to max capacity yields 8380ml 0r 8.38 liters of suspended water at 10% relative humidity. 

Bleeding over the couple hours it takes to fill the tank takes care of a loot of the water, but 8.3 liters would still overwhelm any desiccant system commonly available to the common airgunner, and my observations say this isn't the case. So, I'd say there is something wrong with the math.

Oh the joys of fluid dynamics, math, conversions between systems, and the rest.



If you are going to use metrics for your calculations which is much easier, it's better not to mix them with imperial imputs when constructing equasions. There are also other factors appart from reletive humidity to consider when estimating the total amount of liquid water that will result from compressing 74 cubic feet of air into a .240 cubic foot bottle. If you were to get 8.3 litres of water from compressing that much air, the water alone would take up more space than the bottle could hold. It looks like it's back to the old drawing board for you.
Click to expand...
Click to expand...

Absolutely correct. Back to the drawing board. There is obviously something wrong with the logic or the conversions or the math itself. While I am much more familiar with Imperial, metric makes math simpler. I'm wondering if my initial conversions are where the problems reside. Observation of my little 88 cubic inch tank says I'm not getting any water (I think that 88ci is equal to 16 cubic foot compressed, which is whole lot of liters.). Sill, no sign of water after repeated fills. This leaves me totally confused.

At any rate, maybe I'll figure it out over time. Something like this usually takes me a while to slog through, but I'll get there eventually. I have a feeling the 2095 liters conversion might be a problem, so I'll contact the manufacturer and find out what they say.


 
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It is not the amount of water you get out, but the amount of water that gets into a pcp.

Volume wise, it does not take much water over the lifespan of a pcp to damage it. 

For people who fill tanks I notice that nobody ever mentions tipping the bottle upside down to do a quick purge. There isn't a tube in the tank to prevent water from exiting is there?



Allen


 
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As far as volume of air humidity is still I believe it is still in relation to actual space you have so you may have 74 cubic feet of air but it is still in a space less than that of a 5 gallon bucket. which is only 0.668403 cubic feet. 

and just because the outside air is 10% humidity does not mean the air compressed is not capable of becoming 100% but even at 100% that is not much water content in itself. 

It is not how much water that gets into the system but the fact that water can get into the system and how effective of a device you have at stripping all the water out of the system.
 
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