Hi Guys,

Ive been reading up on adjusting the OPV on Gaggia Classics and wanted to see what the thoughts are on here?

Its suggested that the machine may be way off 8-9 bars causing the flow rate to be too great. Now without a pressure gauge connected to the group head its recommended to run the blind filter and messure the amount of water going back to the water tank.

I had heard keeping the pump going with the blind filter in wasnt a good thing for the machine but others are saying you should be seeing 120-125ml per 30 seconds which roughly works out to 8-9 bar?

My machine is 4 months old im pretty happy with how its making espressos but would like everything right if it makes life easier.

Any thoughts welcome.

Cheers

PaulN

In the newer Classics, I think they are set to 11 bar when leaving the factory, to be pod compliant.

As long as you don't leave the pump running too long, I don't see how putting a blind basket in your classic will hurt it. I know Gaggia does not recommend backflushing, but I think this is a CYA/lawyer move, and as far as I know, there is no technical reason for this recommendation.

If it was my classic, and I didn't want to make a pressure gauge (BTW, I did make one for my classic), I would measure the flow rate while backflushing, compare it to the Ulka chart for your pump, and see if your flow makes sense for 11 bar. If it does, then it should be pretty easy to set it for 9 bar.

On my very old Classic, I think one full turn of adjustement to the OPV was about 1 bar change.

Randy

Thanks for that. It's amazing all the common knowledge stuff you guys knows that us newbies pick up lol

If using the blind filter to work out the the flow rate gives a good indication of the bar then it sounds a plan. Wonder if there's somewhere in the uk I could rent or borrow a pressure gauge from?

Cheers

PaulN

I highly recommend making a pressure gauge.... I did the backflow test against it and it was 50 PSI off...

I just threaded a pipe reducer (3/8 x 1/4 Watts part # A-765 LF) onto a regular water pressure gauge for hose bibs, 135psi is your goal

+1 for pressure gauge testing...

your pump's maximum pressure is dependant on the amount of current that's going to it...for a given voltage X your pressure should be Y. Now, change the voltage at all (say you're running a couple too many appliances on that circuit, for example), and the maximum pressure the pump reaches will change, and the water debit given a certain tension on the spring in your OPV will also change.

People have reported success with this method, but it seems to me like trying to hit a bullseye at the shooting range while wearing a blindfold.

PaulN wrote:Hi Guys,

My machine is 4 months old im pretty happy with how its making espressos but would like everything right if it makes life easier.

Any thoughts welcome.

Cheers

PaulN

There's a lot of good information in the Yahoo Gaggia group about adjusting the OPV.