Air compressor filter / water separator recommendations?

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Forum topic by Vrtigo1 posted 06-01-2012 03:47 PM 21656 views 0 times favorited 6 replies Add to Favorites Watch
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434 posts in 3019 days

06-01-2012 03:47 PM

I was recently spraying a project using my trusty HF spray gun and I noticed that it had developed a small air leak where the gun connects to the hose and some water was coming out of the hose at that area. I started looking at filters on amazon and gather that there are filters that take out particulates and there are filters that take out moisture, and I guess I probably need to get both. Prices ranged all over the place and none of them really had consistently good reviews.

I also saw something in one review about moisture separators not being effective unless they were mounted a good distance away from the compressor because if you connect it right at the compressor the air is too hot. I have a retractable hose reel mounted to the wall right above my compressor and it only has a very short (i.e. 3’) hose that connects it to the compressor, so I have to mount the filters right next to the compressor.

I only spray occasionally, most of the time I am using the compressor to run a brad nailer or blow off nozzle. Looking for any recommendations on filters / filter setup.

Also, I know you’re supposed to periodically empty the compressor to get rid of the water that builds up inside, but I’ll admit that I haven’t done that in over a year. There’s only a couple inches of clearance at the bottom so it’s impossible to get the water to go anywhere but all over my garage floor, and the compressor is so large and heavy it’s not really practical to move it outside to empty it. How do others handle emptying the water from stationary compressors?

6 replies so far

View Tennessee's profile


2873 posts in 2541 days

#1 posted 06-01-2012 03:59 PM

Most people I know who have stationary compressors take the time to release all the air, take out the drain valve, put in a close nipple, a 90’ and then a longer pipe with a valve on it to get the drain out from under the tank. Black pipe will work. Use a ball valve. Crack the valve slightly when you drain off the air, and if you don’t have too much pressure built up, 20-25 lbs., you can use a gallon milk jug to catch the water with the valve just cracked.
If you have not drained your compressor in a year, depending on where you live and when you run your compressor, you could have multiple inches of water in there.
If you have a fair sized tank, you can put the filters fairly close, the air cools pretty quick inside the tank. My last filter seperator kit was mounted no more than a few inches from the outlet on a thirty gallon tank, and it ran fine. I believe you can also get them from HF if you look around.

-- Tsunami Guitars and Custom Woodworking, Cleveland, TN

View cracknpop's profile


295 posts in 2376 days

#2 posted 06-01-2012 04:49 PM

In the humid Midwest, water in the air compressor can become a much bigger problem when spraying a finish. Drawing from my experiences growing up in an auto body shop… I regularly drain the tank on my compressor (easier to wipe water from the floor than sanding it out of the finish coat).

I also have a 30’ air hose connected to an air filter similar to this one (|1&pl=1&currentURL=%2Fpl_Air%2BTool%2BAccessories_4294813345_4294937087_%3FNs%3Dp_product_qty_sales_dollar%7C1&facetInfo= ) that I will plug into the 50’ air hose attached to my compressor. Mount the air filter higher than your compressor if possible (harder for water to flow up hill). I only use this hose and filter for spraying.

While trying to finish a large project when the humidity was particularly high, I coiled the hose from the compressor to the air filter into a cooler packed with ice to help condense any moisture in the air line before it reaches filter. May be a little overkill BUT… I have NO water in my spray finishes.

If this set up ever starts to fail, I have another filter canister that holds a whole roll of toilet paper to catch any moisture in the air line… but for now, the toilet paper stays in the bathroom.

Hope this helps.

-- Rick - I know I am not perfect, but I will keep pressing on toward the goal of becoming all I am called to be.

View dbhost's profile


5726 posts in 3259 days

#3 posted 06-01-2012 05:39 PM

For starters, you need to drain that water from the tank. You will ruin finishes as well ans pnuematic tools shoving wet air at them…

Like was mentioned above, remove the drain valve, and install a short radius street elbow, and then a piece of pipe / nipple long enough to get out from under the tank, then install a ball valve. Not sure what the problem is with spitting water on a garage floor, but just let it go. If you HAVE to keep it off the floor, plumb the drain all the way outside and blow the water / air into a flower bed or something…

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View pintodeluxe's profile


5706 posts in 2840 days

#4 posted 06-01-2012 06:02 PM

I use an in-line water trap at the compressor. I purchased it at a local hardware store for $10. It has lasted 15 years and counting. I drain my compressor after each use to prevent water from building up, and I have never seen water contamination while spraying finishes.
Good Luck!

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View gfadvm's profile


14940 posts in 2717 days

#5 posted 06-02-2012 02:31 AM

Placing an inline water trap at the compressor did not work for me (I think because the air exiting the compressor is too hot for the water to condense). Next, I strongly encourage you to drain your compressor often for 2 reasons: to keep water out of your airtools and spray; second, to keep your pressure tank from rusting out and exploding! I plumbed mine to the edge of the base where I could get to the valve easier and then connect a piece of tubing to drain water away from the compressor.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View Vrtigo1's profile


434 posts in 3019 days

#6 posted 06-22-2012 06:21 PM

Sorry to bring up an older thread. I ended up plumbing in one of the standard hardware store air/water filters about 10” from the outlet on the compressor and this seems to be working well. I can’t believe I didn’t think to also plumb a line from the drain to get it out from under the compressor (duh!), so I will do that as well. When I put in the filter I also drained the tank and it had maybe a cup to a cup and a half of water in it which was less than I expected. The reason I didn’t want to dump water on the garage floor is I expected it to be rusty and didn’t want to stain the concrete. Thanks for the tips they were very insightful.

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