Air Line Water Seperator Location

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Forum topic by bilyo posted 07-31-2019 10:55 PM 549 views 0 times favorited 7 replies Add to Favorites Watch
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1345 posts in 2158 days

07-31-2019 10:55 PM

I have a small 10 gal compressor that lives most of the time in a closet next to my carport. When I use it for spraying I connect what ever length of air hose I need to it; usually not more than 50”. I have a water filter/separator but, the only place to mount it is next to the compressor. I know it should be closer to where the gun will be used but, this is not the same place all the time. I’m wondering if putting the separator next to the compressor along with an in line desiccant type filter would work OK or if the separator will do any good at all located there.

7 replies so far

View johnstoneb's profile


3167 posts in 3228 days

#1 posted 07-31-2019 11:16 PM

The filter separator should be close to the compressor you want impurities removed from all the lines not just the tool being used at the time. There are small filter available to put on the tool to catch dirt etc. Your moisture is produced in the compressor tank. You should have a drain to drain the tank and traps that are drainable at each drop.

-- Bruce, Boise, ID

View bilyo's profile


1345 posts in 2158 days

#2 posted 08-01-2019 12:18 AM

I’m not sure why but, I was under the impression that the water trap should be near the gun. Yes the compressor tank has a drain in the bottom and it gets drained after every use. I don’t have any air plumbing per se, just the hose that goes directly from the compressor to the gun. So, are you suggesting that a desiccant type filter near the gun is sufficient

View CaptainKlutz's profile


4350 posts in 2550 days

#3 posted 08-01-2019 06:58 AM

Water in compressed air can happen in many places.
Where to put your filters depends on situation.
The key to remember is the dew point impacts where the moisture is released. When air is hot, the water is absorbed; and does not release until it cools down below dew point. Period.
Much of water released from compressed air is found in tank, as that is where the air cools down, and releases the water.
But if the air demand is high, and does not cool below dew point until it runs through 100 feet of metal tube, then it gets released in lines.
If the air does not cool until it is atomized at tip of spray gun, then you spray it with your finish.
What this can mean, is might need filters in all 3 locations!

In a perfect shop, or commercial spray applications; you install a refrigerated drier. It is just like an AC unit, but it cools down the compressed air. The water desiccant/filter is installed right after the drier. Goal is drier pulls the dew point below the average temp drop of the atomized stream from a paint gun. ~32-38F dew point is a normal range. Even with a drier, you still put a filter at spray room, to remove any contamination from condensation or crud inside the lines.

Since compressed air drier can cost thousands of $$, most home shops use alternate means.
- Some folks install cooling coils between their compressor and tank to lower temperature and get more water released in the tank.
- If air demand is low enough, simple desiccant filter can remove water. The drawback is they require very regular maintenance. How much depends on where you live and average humidity level.

Suggest that most folks put particulate filter and water trap at compressor, and also put water trap + desiccant filter at end of any lines feeding a spray area. This allows you to capture moisture at tank, and then capture any moisture created in lines before the spray gun. This also reduces the maintenance on desiccant for tools that don’t need dry air. When humidity is very high, can even add a filter at base of gun to reduce the chance of water ruining your sprayed finish.

#IAMAKLUTZ, not an expert. But I have messed around with compressed air systems for commercial operations, and had paint spraying capability at home for 30+ years.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

View Underdog's profile


1650 posts in 3091 days

#4 posted 08-01-2019 10:38 AM

Capn’ might not be an expert but he’s giving you the straight scoop.

When I worked in a local shop, the compressed air service designed our setup with a condensate drain directly under our “wet sump” which was simply the tank for the backup piston compressor. This tank and drain was used by both the screw compressor and the piston compressor to get rid of as much water as possible before going to the refrigerant drier. After that I think there were two more condensate drains in the lines going to the “dry sump” which was a large tank inside the building, and also one in the bottom of that tank. The two inch line going around the building had drops every 20’ or so with ball valves at the bottom to drain any moister that collected at the low points. I also had a desiccant drier and a ball valve at the CNC router to ensure nothing got past that point. Usually the ball valves weren’t needed until something else failed – like the drier unit failing or the wet sump condensate drain filter getting stopped up.
If you can afford it, a screw compressor usually produces a lot less moisture.
The more water you can prevent at the source the better.

-- Jim, Georgia, USA

View ibewjon's profile


2355 posts in 3848 days

#5 posted 08-01-2019 11:22 AM

A larger tank will allow the air to cool before use. With a small tank, the compressor runs often and the air doesn’t cool enough.

View farmfromkansas's profile


220 posts in 669 days

#6 posted 08-01-2019 04:53 PM

I bought one of the water separators from a commercial air compressor company, and was told to mount the filter 3 or 4 ’ from the compressor, to allow the air to cool so the filter would work properly.

View bilyo's profile


1345 posts in 2158 days

#7 posted 08-02-2019 01:19 PM

Thanks. I’ll place the separator next to where the compressor is most of the time and then use a desiccant filter near the gun.

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