Fred Munro munrof at sympatico.ca
Tue Oct 28 18:16:24 PDT 2008

Most lab supply shops will have water driven venturi vacuum units for around
$10 or so that are designed to mount on a lab faucet. They will pull around
20 inches Hg vacuum. You can hook it up to a garden hose for the water
supply. Years ago I used one of these in series with a dry vane vacuum pump
to pull 24 inches Hg on a used central air system I installed in my first

Fred Munro
'97 S6

-----Original Message-----
From: quattro-bounces at audifans.com
[mailto:quattro-bounces at audifans.com]On Behalf Of George Selby
Sent: October 28, 2008 12:56 PM
To: quattro at audifans.com
Subject: Re: Envirosafe

At 12:25 PM 10/28/2008, you wrote:
>A home style compressor is pretty useless for this.  I have a similar
>venturi unit, and it only pulls a decent vacuum on a BIG industrial
>compressor.  Also good to keep in mind that the compressor will be
>running constantly for the half hour of so it takes to establish a decent

I have the same type unit, and it works OK for me on a 4HP
compressor.  It is really useful to see if you have any leaks (pull
it as low as it will go, then close the valves and see if it holds
vacuum.    By pulling the vacuum in about 3 stages, allowing the
compressor to recover in between stages, I can get the vacuum down to
within a pound of the specs, which has always worked for me.  The
biggest problem I have is moisture starts accumulating inside the
venturi device where the air from the compressor comes out, and this
starts interfering with the pulling of the vacuum.  So I would
recommend having a moisture trap on the line from the
compressor.   One final note - it is very loud.  If you have nearby
neighbors, the combination of the air compressor running contantly
and air coming out at full speed is quite obnoxious.

George Selby

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