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Backflushing and the OPV
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Gig103
Senior Member


Joined: 12 Feb 2012
Posts: 244
Location: Arizona
Expertise: I like coffee

Espresso: Crossland CC1
Grinder: Baratza Vario
Drip: French press!
Posted Wed Jul 25, 2012, 11:41am
Subject: Backflushing and the OPV
 

I was wondering - if I am backflushing, and let the pressure build up too much before I shut off the pump, might the detergent make its way into my reservoir? SCG put out a new 'tip sheet' on their FB page that recommended leaving the pump on for 15 seconds which seems awfully long.
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dyqik
Senior Member


Joined: 7 Oct 2011
Posts: 383
Location: Cambridge, MA
Expertise: I love coffee

Espresso: Bezzera BZ07 PM
Grinder: Baratza Virtuoso Preciso...
Vac Pot: Cona D
Drip: Bona-Vita, CCD, Aeropress.
Roaster: Gene Cafe, Modded Poppers
Posted Wed Jul 25, 2012, 11:58am
Subject: Re: Backflushing and the OPV
 

The OPV is between the pump and boiler (this is so only cold water is returned to the reservoir, as hot water can damage vibe pumps).  The PF/group is pressurised through the OPV and boiler, and so can't be at any higher pressure than the boiler (and will be slightly below the boiler pressure if there's any kind of leak around the group), and so there can't be any significant flow back into the boiler.  In turn, there isn't any flow back from the boiler to the OPV, so there's no risk of backflush detergent entering the reservoir.

At least this is the case on my Gaggia Classic.  I'm sure there's one machine or another that does it differently.
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