I have a 2 HP, 20 gallon Craftsman compressor. I drain it about every five
years and never release the pressure at the end of the day.
I have been using it since 1973.
It was getting really hot when shingling so I changed the oil last fall.
Don't know if that helped--maybe I just slowed down a bit. :-)
You'll have to go back and drain it again after the tank cools down. There will
be more condensation as the cooler air can't hold as much moisture in its
And as others have pointed out, there's draining condensation and there's
draining the tank completely. If you'll go back to drain the condensation after
the tank is cooled, there's no reason why you couldn't leave it pressurized. If
you're not willing to do that, you may well end up with rust eating the bottom
of your tank out over time.
In general, no. However a machine that has a slow leak down somewhere
and is going to be switched off for long enough to empty itself is
usually best vented deliberately rather than being left to do it
inevitably itself (or just fix the leak!)
You should of course always blow down the water after any sufficient
use of the compressor. This doesn't mean emptying the reservoir
though. Nor does it require doing if the reservoir has been left full
long-term with the compressor off, except possibly if you've had major
A compressor is a pressure vessel, i.e. it's potentially dangerous if
left pressurised. The risk is small, the convenience and energy saving
of leaving it full outweighs this if we're going to come back to it
later and use that stored pressure.
However if we've got a leak, or we're leaving it for a long time such
that we're _not_ going to benefit from that stored energy, then good
practice is to not leave it lying around. You don't know what it's
going to do, but it ain't going to bake you a cake. There's also the
risk of leaving the compressor powered up (and leaking), which is just
a sizable waste of energy.
Leave the tank pressurized and shut power off to the motor.
The normal failure mode of a tank pressurized within specifications is
to develop a pinhole leak, not to explode catastrophically. So there
is very little risk in leaving it pressurized. Understand that is not
the case if the failure is due to overpressurization. In that case,
the failure can be catastrophic so make sure the pressure relief valve
is properly set and functioning.
I have a 6 gallon pancake compressor by Porter Cable. When I use it
it's only for an hour or two. Afterwards, when I bleed it I see water
coming out of the tank. So I bleed it after each use. It only takes a
few minutes to compress the unit so it's well worth the effort. So my
recommendation is, if you see water coming out when you bleed the
tank, then bleed the tank whenever you are done using it.
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