View Full Version : Air compressor condensate problem.

07-08-2010, 10:12 PM
My compressor is outside on a small slab.
I drain the condensate regularly on the tank. The air comes off the middle of the tank as shown and goes into underground 1 metal pipe for a run of about 65 ft. where it comes up and goes thru the wall into the shop. I get a lot of water out of the first tap in the shop. I have several small air tanks from old trucks and have been thinking about using one to build another moisture trap. I have also considered a good commercial water separator. The underground pipe seems to be working to condense the water vapor in the line so should I let it do its thing then run the Air through a water separator. I have small water separators and coalescing filters on individual points of use that need them. I also have a purge valve where the line goes into the shop and even though I flush that underground line regularly I am still getting more moisture than I want to filter with these filters/separators. My fundamental question regards where to concentrate my effort. Should I clean it up better at the compressor end or let the pipe do its thing and catch it on the shop end?

07-08-2010, 10:27 PM
There are a few different ways to go about this.

An air over after cooler such as an AC condenser coil added just after the tank along with a fan to force air through it is one way.A water trap just after the condenser would most likely catch 90% or better of anything left.

Another is a water cooled heat exchanger,basically a double pass tube echanger with a water source as the cooling medium.Better at removing condensate,but uses lots of water,alright if you have a pond nearby,not so good on city water.It can be plumbed in between the compressor and tank and the condensate dropped out BEFORE it sees the tank.

A refrigerant cooler is another and really best option,but probably the most expensive also.

Dr Stan
07-08-2010, 10:32 PM
A refrigerant cooler is another and really best option,but probably the most expensive also.

This is what I would also suggest.

What is probably happening is the relatively cooler ground is causing the moisture in the compressed air in the underground pipe to condense. A water trap at your first outlet would probably help, but most likely not to your satisfaction.

07-08-2010, 10:51 PM
Put an automatic drain on it. Mine cycles on every 45 minutes.

07-08-2010, 11:00 PM
Put an automatic drain on it. Mine cycles on every 45 minutes.

But,the air in use is still hot and ladden with moisture,his problem comes in when it hits the line buried in the cooler ground.

The whole idea is to drop the air temp below the dew point dropping the moisture out.

07-09-2010, 12:17 AM
If I understand what you said, you go out from the compressor, then down 4", horizontally for 65' and then up into your shop.

You have a giant 'U' Shaped condenser that probably is full of water. There is probably more elegant parts, but here is a black pipe trap that would get the water out of the line.


Or and I'm not going to change the pic, you could connect tubing to the spot marked valve and bring it up to ground height and put the valve in a convenient location. Air pressure would blow out the bottom of the trap.

My guess many of your problems would go away with keeping the pipe dry.
My 2

07-09-2010, 12:36 AM
Technicaly, your giant metal pipe should have a water trap and valve at its lowest point and all slope down to that.. But since its a little late for that.. Id recommend a large water seperator right after it enters the shop, since that underground line is basicly just gonna become full of water untill it gets forced out by enough air flow.

On the plus side, after condenseing in that line, the air is probley rather dry.

07-09-2010, 07:09 AM
Install a cheap "cyclone" water separator. May be integral with or separate from a regulator. You will soon see if there is any condensate in the transparent bowl. There is a small hand-operated drain/valve on the bottom of the bowl.

If it were me installing that under-ground pipe, I'd have graded it at least 1:100 (say 1/8" per foot) to a drain ("ball") valve in a pit in the shop. Pump the pit out as required.

07-09-2010, 11:01 PM
a buddy has the same set up-outside AC,underground pipe,taps about 4 ft above the floor. he put a semi-truck air tank below the first and last taps mounted them vertically and drains them once a week. turn off the juice,open the petcocks, let it blowoff and drain, then turn the power back on and let it blow out any more water for a minute or so. he gets about half a coke bottle a week out of each tank.

07-09-2010, 11:58 PM
My compressor is outside on a small slab.

I can see why you have water issues. The air is warm and humid that you are sucking in. If you have AC in your shop, at least let the compressor suck in drier air.

You are trapping all of the water underground. If it were me I would replumb it so the pipes are overhead and have a slope in it so water drains back to a central point with a drain.

I have one run of 3/4" pipe that I goofed on and it has no slope. I have to purge that line weekly. All of my other runs are OK.

07-10-2010, 11:07 AM
Any reason that the airline cant be rerun overhead? Then with the fan-cooled AC coil aftercooler, you would have a fighting chance.