Porter Cable's instructions say to bleed it every day. I thought that
was a bit excessive, and left mine full for quite a while. The other
day, I emptied it, thinking some water might have built up. Indeed,
holding it up so the exhaust was at the bottom, a considerable amount of
water came out! Had to hold it over the sink. Perhaps I'll empty it like
that every few of weeks now.
Jedd Haas - Artist - New Orleans, LA
You are on the right track.
Actually the compressed air does not create the condensation. It is the
heat generated from compressing the humid air that causes the condensation.
Take a glass of ice water out into a hot humid place and you will get
condensation on the outside of the glass. Once a compressor has stopped
running and cools the condensation stops. The longer the compressor runs
and the more heat generated the greater the condensation.
Soooo, if you let the compressor cool and bleed off just the excess
condensation there should be no more water build up when the compressor sets
Typically however, no one remembers to return to the compressor to bleed the
condensation after the compressor has cooled. Bleeding is a good practice
and total bleeding insures that you don't have to stand around waiting for
all the water to blow out.
Typically also, the faster and fewer times a compressor cycles the less
build up of condensation you will get regardless of the volume being
If you fill an empty tank form a cool compressor tank that is not running,
there will be no condensation generated.
Incorrect. It is *exactly* the compression that causes the condensation: water
that is vapor at ambient pressure can be condensed into liquid by increasing
Increasing temperature *cannot* cause condensation; quite the opposite, in
Yes, that's because the warm water vapor in the air is being *cooled* by the
cold glass, and condenses onto it. Condensation is the result of a decrease in
temperature (that's why dew appears overnight, not in the middle of the day)
or by an increase in pressure.
Again incorrect. As long as the pressure remains high, the vapor will remain
Once again incorrect. It's the pressure, not the heat, that condenses the
Still off the mark.
Nonsense. The amount of condensation depends on the amount and humidity of the
air being drawn into the compressor, and the pressure to which it is
compressed. Nothing more. It has absolutely no relation to the compressor duty
That's because you're *reducing* the pressure. It has nothing to do with the
Doug Miller (alphageek at milmac dot com)
After reading your post, it reminded me of the fact that in order to
bottle liquid oxygen, they have to cool *and* put it under high pressure
to get it to condense to a liquid, but I never would have thought to
apply this principle to an everyday compressor. Good info.
So Doug, I suspect you believe it is the pressure from "your firm grip" on
a glass of ice water that causes the warm humid air surrounding the glass to
cause condensation on the cool side of the glass.
Of course not. Vapor condenses as a result of being compressed, or cooled, or
both -- but never as a result of being heated. Warm humid air surrounding a
glass of ice water produces condensation on the side of the glass because the
temperature of the surface of the glass is below the dew point. The water
vapor condenses because it is cooled.
Doug Miller (alphageek at milmac dot com)
Compressed air doesn't create moisture; it only compresses what already exists
in the atmosphere that day. The process of compression creates heat, which will
allow more moisture to stay in the vaporous state. Later, as the tank cools
down, that vapor may well condense since cool air can't hold as much moisture as
As a former scuba instructor, I'd always taught my students to never let a tank
run completely empty as positive air pressure kept moist ambient air from
entering the tank. However scuba air is MUCH drier than shop air. Given that
shop compressors don't usually filter out moisture as scuba compressors do, it's
a bad practice to just let that moist air sit in the storage vessel, rusting it
out over time.
Bottom line... it's probably better to dump the air when you're done... at least
for shop compressors.
Well, I figured it was worth 10 bucks to try it out. When I went to
retrieve the URL, I noticed the 100psi limit. That may be new. I don't
recall noticing that limit at the time I bought one several months
ago. I run my 80 gal compressor at 135 psi shutoff and haven't seen
any adverse effects.
Every few days, or whenever I think about it, I open the manual drain
valve to verify that it's keeping the tank dry. So far, since
installing the automatic drain, I've never had a drop of condensation
come out the manual drain when I check it.
Tom Veatch <firstname_lastname AT pixius dot net> wrote:
I bought one of these from HF, when I bought a new compressor
recently. I must have spent the better part of a day or so trying to
figure out a way to install this. The main problem I ran into is with
the air hose supplied and the compression fittings it uses.
Basically there weren't enough parts there to splice this device into
the system as they don't give you any additional compression fittings.
On my compressor, there's a solid copper line running between the
tank and the regulator. So I would need two more fittings to
rework things so that the automatic drain valve could be tee'd in
between the tank and the regulator.
I spent several hours trying to find more of those fittings locally,
but none of the hardware stores had them and HF itself does not
sell them. Perhaps a specialized industrial supply would have them,
but after spending a few hours trying to hunt stuff down, I gave
up and returned the device. The device itself probably works fine,
but you'd likely need to dig up some other type of way to splice
it into your system that uses some other type of fittings and hose.
It would be nice if they'd supply additional male and female
compression fittings with the device, even if that increased the
price of the device by a few bucks.
In the end, I found it's easy enough to just open the drain at the
bottom once a day and let it blow out the accumulated moisture.
If you want to reply via email, change the obvious words to numbers and
I moved the drain plug to the end of a 3' length of air hose on my small
vertical, where it is much more accessible.
The air hose holds quite a bit of water that would otherwise be in the tank,
and, unlike the tank, is rustproof ... and gravity does the work.
It is a simple matter to open the cock slightly every other day or so and
let the water in the hose squirt out, and draining the tank this way doesn't
even cause the compressor to cycle on.
| I moved the drain plug to the end of a 3' length of air hose on my
| small vertical, where it is much more accessible.
| The air hose holds quite a bit of water that would otherwise be in
| the tank, and, unlike the tank, is rustproof ... and gravity does
| the work.
| It is a simple matter to open the cock slightly every other day or
| so and let the water in the hose squirt out, and draining the tank
| this way doesn't even cause the compressor to cycle on.
Great idea - consider it stolen :-)
DeSoto, Iowa USA
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.