Re: 3-way valve abomination
- From: Paul Pratt <paul@xxxxxxxxxxxxx>
- Date: Mon, 17 Oct 2005 11:26:59 +0800
On Sun, 16 Oct 2005 15:58:39 GMT, Andy Schecter wrote:
> No one seems to talk about this, so I'll take a stab at it.
> 3-way valves http://www.benissimo.nl/3way/ are an abomination. Apparently
> they're in there so the barista can immediately remove the PF after a shot
> without the messy "portafilter sneeze." Granted, they are effective for that.
> But the unintended result is that espresso from the portafilter backs up and
> coats the inside of various supply tubes and components. There it sits,
> growing old, waiting to taint the next shot.
> I've never used a lever machine, but as I understand it, levers do not have
> 3-way valves. People who feel that levers make superior espresso seem to
> concentrate on the declining, pulseless pressure profile as an explanation.
> That may be an important factor, but is it possible that the lever's "clarity
> of flavor" may also result from an uncontaminated product path?
> I don't know enough about the Synesso and the new LM machines to speculate on
> how they address this situation. But from what I know so far about pump
> machines, only Versalab has bothered to tackle the problem of 3-way
> contamination with a fresh design.
> Of course, cheapo home pump machines don't have 3-way valves, so they could be
> superior in terms of flow path contamination. But they have many other issues
> with temperature and pressure control that probably overshadow any possible
I think you have a very valid point and one which I agree with. I have
often thought about this contamination problem. Once you take apart a
machine and see all of the oils and dirt that look like they have become
one with the metal it. Let me just run through the Linea machine since I
am familiar with it. Most of us have seen that the brew path on that
machine is long. The "clean" water leaves the boiler and goes via a small
pipe to the 3 way valve hanging below the group. After that the water goes
through the valve (when brewing) and through a small pipe into the group
and then through the infamous banjo tube and then onto the diffusor and
then the coffee. That is a distance of 12-15 cm.
After brewing the pressurised water goes back the same route and exits via
the spare port on the 3 way. So in actual fact the route from 3-way to
coffee is "contaminated".
This is confirmed by examing groups that have been taken apart. By far the
hardest parts to clean on machines I work on are the parts mentioned - 3
way valve body, banjo tube and diffusor block. The coffee oils are really
really hard to remove and no amount of magma like puro caff solution will
remove them. The only way is to scrub or use a wire brush.
The same is true of other machines as long as the brew water and waste
water use the same path there will be oils and dirt inside. Even the most
stringent of shop cleaning rituals will not remove all that by
backflushing. Sure it gets most of it but not all.
So maybe the least contaminated machines are ones where the solenoid is
clamped onto the group right before the diffusor block which minimises the
shared path of brew water and exhaust water. Even the famous Marzocco
manual group (aka paddle) has it's share of oils inside even though exhaust
vent is just millimeters away from the group. I am fortunate to have
several manual Marzoccos and to get each group clean inside was not easy as
the coffee oils and dirt were literally etched into the brass. The only way
to really get them clean was to refinish the surface of the brass.
My own taste buds aren't good enough to distinguish between subtle taste
differences but the evidence of oil and dirt build-up is there if you take
your machine apart.
- 3-way valve abomination
- From: Andy Schecter
- 3-way valve abomination
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