DISCLAIMER: This information is accurate to the best of my knowledge,
however, none of it is definitive. If you try any of these suggestions
and break your machine, neither myself or any of the other people I quote
can be held responsible.
Advanced Cleaning: Backflushing
Backflushing the Silvia is NOT recommended by the Rancilio S.p.A. -
Any damage you incur from backflushing a Rancilio Silvia is not covered
under warranty, so performing this procedure is at your own risk - don't
come crying to me if the seals on your pump fail. I repeat, this
procedure is at your own risk, and can void your warranty.
Despite the above, this has not stopped many Silvia owners from
Randy Glass on alt.coffee explains why you might want to backflush:
"Over time bits of coffee debris are carried with the water through the
3-way valve towards and into the drip tray. This happens during a pull
when the switch is turned off and the built up pressure is directed
through the valve. Not all the coffee makes it into the tray. Some of
it sticks in the valve. Eventually you will need to backflush to clean
To backflush, you will need a blind backflush
insert, sometimes called a blind basket, and espresso machine cleaner.
Now I quote a Randy Glass post from alt.coffee:
"Backflushing is no more dangerous to the machine or yourself than
choking the machine with a too fine blend. The machine works far
harder when you let it run for ten or fifteen seconds waiting for
espresso to drip out then when properly backflushing.
"When backflusing I would caution that:
"1) You do not leave the pump on for more than about one-half second
once the pressure builds. Turn it off and let the pressure be
displaced through the 3-way valve before repeating. Once the suds from
the cleaner are seen in the drip tray stop backflushing and let the
cleaner do its work. I just let it sit (with the machine's main switch
OFF) and let it soak for ten or fifteen minutes.
"2) Do not backflush a hot machine. Let the machine cool to ambient
room temp before backflushing so that the cleaner does not get baked
onto hot surfaces making it more difficult to rinse off. Once step one
is done, turn the machine off and let it sit with the heating element
off and the machine still relatively still cool before proceeding.
[See note below from Al Critzer. After this, Randy mentioned that he
pre-dissolves his cleaner with hot water and runs the solution bit by
bit by adding more to the portafilter each run.]
"3) Use a cleaner designed for such purposes such as "Urnex Espresso
Machine Cleaner" and NEVER run this stuff through the pump or
boiler!!! It is not a descaler and this WILL damage the machine.
"4) Once the cleaner has done its job, clean out the portafilter,
reinsert the blind filter, and turn on the machine again. Continue
the backflushing procedure (turn on the brew switch, wait the one
second or so for the pressure to build, turn off the brew switch
and allow the pressure to be fully relieved through the 3-way valve)
until clean water comes out of the 3-way valve.
"5) Once that is accomplished, remove all the parts you can and
manually clean with portafilter brush and towel using clean, hot water.
Clean as thoroughly as possible.
"6) Once done, reassemble the machine and pull one or two double shots
and discard them. They could contain some residual cleaner, and will
taste terrible if not be actually hazardous to consume. The machine
will need a bit of seasoning as well. [Meaning what I am not sure.
I'll have to ask sometime!]
"Backflushing improperly MAY void the warranty, but allowing the 3-way
to eventually clog up with coffee debris will necessitate disassembly
of the valve for cleaning which would also presumably void the
warranty if done improperly. Just don't do it improperly."
Al Critzer (also alt.coffee) disagrees with Randy on one major point:
"Backflushing should be done with the machine at operating temperature.
Purocaff, pulycaff, Urnex, all rely on hot water to emulsify. We all
know that coffee has minimal reaction to cold water, and coffee
residues are no different. Backwashing with cold or warm water has the
additional negative side effect of depositing detergent residues in
the group and solenoid valve. You don't want that in your next cup of
coffee." [I assume that Al would both backflush and let the cleaner
sit with the machine on and hot in steps 1 and 2 above.
You have the information now,
dear reader, and you can make your own call on this one!]
Randy Glass also
notes that even with backflushing, some gunk still builds up in the
solenoid valve and will eventually cause it too leak. Dissassembly of
the valve will be required for a more thorough cleaning. He implies
that six months to a year is about right for valve cleaning. Instructions
on this are linked to from my main Silvia
NOTE: I backflushed my Silvia every few months, and always heat it
up beforehand. It makes a noticable difference in how the espresso
tastes - always a great improvement.