Check Valve for Moisture Filter - "Gold Filter"

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hollowpoint

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Nov 13, 2017
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California, United States
I've had a few people ask me about this, so I thought I'd create a post to share the info with everyone though I'm not the first/originator and take no credit.

I recently added a check valve to the end of my moisture filter. I did this for 2 reasons, to frequently open the high pressure bleed screw on the Yong Heng compressor to remove accumulated water, and to prevent air from my SCBA tank from escaping in the event of a compressor/fitting/hose failure. In the early days of running my compressor, I had 3 different Chinese quick disconnect fittings fail on me around 4000psi, and ever since then I'm constantly thinking about the what-ifs when a large volume of high pressure air gets released.

Last week I fired up my compressor with check valve installed and filled 2 of my SCBA bottles. With the check valve on the moisture filter output side, I cracked the high-side bleed screw about every 2 minutes and in a 10 minute session I purged enough water to thoroughly dampen a rag. In order for this to be effective, note that the moisture filter (input side) must be located HIGHER than the compressor's output so that moisture can pool up by the high pressure bleed screw.

Here's a picture of my check valve setup:

1533286728_8970541885b641948edf8b8.41162254_filter check valve2.png


This is the breakdown of the exact parts I used. You could probably save some money by using less stainless steel fittings or finding some fittings on eBay/AliExpress, but due to my bad luck with cheap fittings...I'm ok with paying the premium.


The zinc plated fittings from August Industries are stamped made in China, but rated for 6000psi service. They work perfectly fine, but I'm replacing them with stainless steel fittings just because. The male Foster fitting from Air Tanks Plus comes with a little check valve in it, but for this purpose I've removed it. It functions as a straight-through fitting. With all the various fittings available out there, it's possible to install a check valve with fewer fittings than I've outlined above, but I've ordered these parts over the course of a month or so with different end goals in mind. If any of you guys go down this route using quick disconnects, I'd recommend you don't mix/match 1/8 NPT Foster fittings and 8mm quick disconnects from China because there's the possibility they won't stay coupled at high pressures even though they might seem to connect to each other. I've spent a ton of money (more than the cost of the compressor) to convert my compressor and fill station over to NPT so I don't have to deal with NPT, Metric and British. It was painful to get here, but I'm hoping it results in less trouble down the road. Let me know if you have any questions!



If this is helpful for any of you out there, I'd greatly appreciate it if you could give me a + Accuracy Thanks!
 
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You can achieve the same result without all those joints and fittings with a $3 non-return 10mx1 male to 1/8 type foster type fitting from Aliexpress https://www.aliexpress.com/item/Paintball-Airsoft-Air-Gun-PCP-8MM-Male-Quick-Head-Connection-Check-Valve-One-Way-Foster-Stainless/32822695201.html?spm=2114.10010108.1000014.7.4b945400SLv5Rh&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.13338.98644.000000000000000&scm_id=1007.13338.98644.000000000000000&scm-url=1007.13338.98644.000000000000000&pvid=58e9a5b7-fe56-4785-a68f-f1b0dedb5499 or eBay. I use NPT one of these, screwed into a female to male, to make a portable male to male, check valve. Always make sure you have a bleed valve on the side that you want to isolate or you won't be able to uncouple anything. One other thing. If the arrow on your housing is the direction of flow you will need to use this fitting on the other end as you want to stop the flow back towards the pump. And lastly, why are you worried about losing a short squirt of air when you open the bleed screw? The amount of air that escapes in this process is minuscule or do you let all the air out of the system when you bleed it?
 
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You can achieve the same result without all those joints and fittings with a $3 non-return 10mx1 male to 1/8 type foster type fitting from Aliexpress https://www.aliexpress.com/item/Paintball-Airsoft-Air-Gun-PCP-8MM-Male-Quick-Head-Connection-Check-Valve-One-Way-Foster-Stainless/32822695201.html?spm=2114.10010108.1000014.7.4b945400SLv5Rh&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.13338.98644.000000000000000&scm_id=1007.13338.98644.000000000000000&scm-url=1007.13338.98644.000000000000000&pvid=58e9a5b7-fe56-4785-a68f-f1b0dedb5499 or eBay. I use NPT one of these, screwed into a female to male, to make a portable male to male, check valve. Always make sure you have a bleed valve on the side that you want to isolate or you won't be able to uncouple anything. One other thing. If the arrow on your housing is the direction of flow you will need to use this fitting on the other end as you want to stop the flow back towards the pump. And lastly, why are you worried about losing a short squirt of air when you open the bleed screw? The amount of air that escapes in this process is minuscule or do you let all the air out of the system when you bleed it?
Click to expand...


Wrong post. My bad.
 
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JU, that fitting will work for the outlet end of the filter only,( keeping pressure from leaking back from the bottle or gun), but it seals in the wrong direction for use on the inlet side of the filter. (to keep the filter pressurized), which is what most of us want. Another point I would like to make is there needs to be a bleed valve for the filter if both ends of the filter have one way valves to keep it pressurized, otherwise you can get it apart when it's pressurized. Also, I don't see a way to seal the threads on that fitting...the end is not flat, so will not seal against the plastic washer in the filter cap hole. You might get away with one of those rubberized washers under the shoulder though, but it looks iffy.

I think a better solution than a check valve on the filter inlet is to use an in-line manual shut off valve, or better yet, install it at the pump outlet fitting. This will allow de-pressurizing the filter for maintenance, but will need to be opened manually, when pump pressure raises close to the filter pressure. I don't know where you could get something small and simple like this that wouldn't leak to atmosphere, under pressure, when it is open and without using a stack of adapter fittings as the original poster shows on his check valve, but I think It could be easy to make if you have a lathe, which many of us have. Another option would be a check valve, (operating in the right direction), with a bleeder screw on it. But probably doesn't exist either.

On my current setup, I could use JU's one way valve on the filter outlet, (if it can be made to seal), so then I could disconnect the bottle fill-hose and connect the bottle to the gun, without loosing the large volume in the filter/drier. 

Comments welcome.
 
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JU, that fitting will work for the outlet end of the filter only,( keeping pressure from leaking back from the bottle or gun), but it seals in the wrong direction for use on the inlet side of the filter. (to keep the filter pressurized), which is what most of us want. Another point I would like to make is there needs to be a bleed valve for the filter if both ends of the filter have one way valves to keep it pressurized, otherwise you can get it apart when it's pressurized. Also, I don't see a way to seal the threads on that fitting...the end is not flat, so will not seal against the plastic washer in the filter cap hole. You might get away with one of those rubberized washers under the shoulder though, but it looks iffy.

I think a better solution than a check valve on the filter inlet is to use an in-line manual shut off valve, or better yet, install it at the pump outlet fitting. This will allow de-pressurizing the filter for maintenance, but will need to be opened manually, when pump pressure raises close to the filter pressure. I don't know where you could get something small and simple like this that wouldn't leak to atmosphere, under pressure, when it is open and without using a stack of adapter fittings as the original poster shows on his check valve, but I think It could be easy to make if you have a lathe, which many of us have. Another option would be a check valve, (operating in the right direction), with a bleeder screw on it. But probably doesn't exist either.

On my current setup, I could use JU's one way valve on the filter outlet, (if it can be made to seal), so then I could disconnect the bottle fill-hose and connect the bottle to the gun, without loosing the large volume in the filter/drier. 

Comments welcome.
Click to expand...

Sorry to correct you but these fittings are only suitable for the inlet side. They flow from the Foster end and block from the threaded end. The advantage of using a male to male portable valve like I described is it can be used in any direction by simply turning it around. It is perfect for joining two female hose ends together. You can make a male to female valve but it will only work in one direction. hollowpoint wanted a check valve as close as possible to the bottle in case a fitting failure caused him to lose a tank full of air. I have had Oring failures that have had the same result. I believe that his fitting malfunctions were probably more a result of not closing the retaining collar properly than the compatibility or quality of the Chinese fittings. I mix and match many slightly different fittings all the time and have never had one fail.
 
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