The pressure is pretty much maxed out at 8.5-9 bar once the pump ramps up (take a few seconds). The pressure shouldn't drop much under flow unless you're pulling a cafe crema. It's difficult to get accurate readings from the Vetrano gauge (marked only at 0, 8, 12, and 15 bar), and the gauge is out of focus in this pic, but you can tell that the pressure is definitely over 8 bar.
That's why I don't consider a built-in pressure gauge to be a necessity. Once you set the max brew pressure correctly (usually to 8-9 bar), there's not much to be gained from monitoring the pressure during the shot. You should hit close to the max pressure every time (unless your pressure is set 'way too high). You're much better off monitoring the shot time, volume, color, etc. - and of course the taste. (Now a realtime brew temp sensor might be nice... :-)
Uh, no. You have to unscrew the gauge (at least) before brewing. This is for setting the brew pressure, not monitoring it during the pour.
Actually, that brings up an interesting point. The measured pressure may be slightly higher using a PF gauge, since there is no liquid pushing out through the coffee grinds. It should give you the maximum pressure setting - anything more will cause pressure to be released through the overpressure/relief valve. I assume it's useful nonetheless (since you can purchase commercial versions).
Has anyone checked for differences between brew pressure gauge readings during a shot, and pressure measurements from a PF gauge such as this one?
Posted Sat Jan 28, 2006, 11:16pm Subject: Re: $10 portafilter brew pressure gauge
Is there a trick for sealing the reducer to the pf? Mine isn't quite 3/8" at the bottom, but I can't seem to get a tight seal even with 15+ winds of teflon tape - and I'm sure I couldn't find metric plumbing fittings anywhere around here!
Posted Sun Jan 29, 2006, 7:54am Subject: Re: $10 portafilter brew pressure gauge
Ozark_61 Said:
Is there a trick for sealing the reducer to the pf? Mine isn't quite 3/8" at the bottom, but I can't seem to get a tight seal even with 15+ winds of teflon tape - and I'm sure I couldn't find metric plumbing fittings anywhere around here!
Sorry to hear this, and wish I could help. Is this a Gaggia PF? I'm using a commercial Rancilio PF, and there's no problem with the seal. All it takes is one twist of teflon tape. I believe 3/8" is the standard fitting for PF spouts.
Posted Sun Jan 29, 2006, 8:50am Subject: Re: $10 portafilter brew pressure gauge
Ozark_61 Said:
Is there a trick for sealing the reducer to the pf? Mine isn't quite 3/8" at the bottom, but I can't seem to get a tight seal even with 15+ winds of teflon tape - and I'm sure I couldn't find metric plumbing fittings anywhere around here!
I had no problem sealing either with a couple wraps.....the thread on my two different PFs are both 3/8 NPT.
Actually....that may be the problem....in the fitting you are using a 3/8" National Pipe Thread, or just a 3/8" "normal" thread....like on a 3/8 nut/bolt? A standard 3/8" thread will NOT work properly...it has to be a tapered pipe threaded fitting.
Posted Sun Jan 29, 2006, 3:27pm Subject: Re: $10 portafilter brew pressure gauge
Actually - there's a few options at the hardware shop - but I think I did have the right one in the begining. I bought a 3/8 x 1/4 FPT coupling. There are some other fittings, flare, compression, etc, but maybe the one I bought is just defective. Of course I would never rule out user error... ;-)
Well, I bought the gear needed for thos pressure guage last night, and tried it this morning. First I tried it with a regular basket in, and it sprayed water everywhere. Then I tried it without, really cranked the PF in there, and it shot water across the room. Both times from the PF gasket area, not the guage connection.
What could it be? My PF gasket is not too old. Is the guage faulty?
Well, I bought the gear needed for thos pressure guage last night, and tried it this morning. First I tried it with a regular basket in, and it sprayed water everywhere. Then I tried it without, really cranked the PF in there, and it shot water across the room. Both times from the PF gasket area, not the guage connection.
What could it be? My PF gasket is not too old. Is the guage faulty?
I've never tried this on a Silvia. Do you ever backflush? If your machine does not spray water with the blind filter in place, it should not spray with a gauge, which blocks the flow just as completely. Your gauge could be faulty, but I don't see how this would impact on water spraying from around the gasket.
I've used this method on two machines (one is a different model Rancilio) using the PF without any basket in place, and never had leakage around the group head gasket. You will definitely get leakage between the PF and the gauge if you fail to wrap the PF and gauge threads with Teflon tape.
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