Gig103 Senior Member Joined: 12 Feb 2012 Posts: 215 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.
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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