Gaggia Classic (adjusting the OPV)

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10,962
Over Pressure Valve

While researching into my own machine (Rancilio) I came across an interesting mod that is done to the Gaggia Classic, according to the link below all Classics are set at 14 bar for coffee pod rather than naked grind use, as 9 bar is around the optimum setting I thought this link would be useful to new Classic owners.

http://coffeeforums.co.uk/showthread.php?3859-Adjusting-the-OPV-%28over-Pressure-Valve%29-Gaggia-Classic

If you want to make yourself a pressure gauge I bought my gauge from these folks

http://www.ebay.co.uk/itm/Pressure-Gauge-air-oil-water-60mm-0-150-PSI-0-10-Kg-cm2-Bar-1-4-BSPT-/130624550050?pt=LH_DefaultDomain_3&hash=item1e69d474a2

the links to the actual fittings are below + PTFE tape

Please check thread dimensions on your own portafilter, if you're happy with results ignore.
 
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1,582
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??? dinnae ken
now I may be wrong(does no happen often though)

but the portafilter threads are 3/8 and the pressure gauge is 1/4 so would be one of these
http://www.ebay.co.uk/itm/3-8-BSP-316-STAINLESS-STEEL-ELBOW-90-DEGREE-150LB-/220565167817?pt=UK_DIY_Materials_Plumbing_MJ&hash=item335ab55ec9#ht_500wt_922

and one of these
http://www.ebay.co.uk/itm/3-8-X-1-4-BSPT-HEX-REDUCING-BUSH-316-STAINLESS-STEEL-/220594588050?pt=UK_DIY_Materials_Plumbing_MJ&hash=item335c764992#ht_500wt_922

with the pressure gauge to make it all fit.

But cheers for the link have a pressure gauge here to do this and was putting off looking for the fittings but this seller is spot on.
 
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antdad
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10,962
Thanks for the clarification, I thought I'd read the Classic filter had 1/4 thread but as I don't have one I wasn't sure.
 
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1,582
Location
??? dinnae ken
Cheers antdad for finally making me move my arse and do this, I have now set my pressure at the required setting( You put doubt in my head to the size so ended up going into somewhere today with the portafilter and checking the size so got the parts from there)

all setup


I had a problem with water coming out the top of portafilter even though I had the basket in but was easily sorted with some PTFE tape round the outside of the basket to make it a real snug fit.
( just noticed should not have had the basket in, that would have solved the leak problem, just re-tested still the same reading so no biggie)
these are cheap as chips to make I got the bends from BSS or something similar and they even do pressure gauges(wish I had knew that earlier) but if anyone wants to borrow this I will post it round. should fit all machines or so I was told most portafilters are 3/8 thread.
 
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antdad
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10,962
Ah good, my bits came through today but I need one because of a new pump installation. Seems little point refining everything else if the group head pressure is way off, was your pressure high as the article suggested it would be?


BTW: Not forgetting your measuring static pressure rather than dynamic, add 1 bar to what is desired.
 
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2,061
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London
Following this with interest fellas, blew all me pocket money on an iPad this month so next month this will be my first mod when I get my Classic.

Let us know your results and Pedro hang onto your gauge, I will borrow it if you still have it when I get mine.

Cheers
 
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1,053
Location
North Lincs
Heck I'm getting out of my depth here....
I'm interested to know how much difference this makes. I'm interested too in having my machine tested...
Does this mean taking the spout off the PF?
Mine is stuck stuck stuck.
Great post and the link is excellent.
Tim
 
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antdad
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10,962
It should improve crema formation and the general flavour quality of your shot, I'm getting sensational crema now I've adjusted mine.

9 bar seems to be the optimium setting and yours is I assume like Pedros set at 14 bar, I guess because it's so high you are compensating for under extraction by wanting to grind finer and tamp harder.
 
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