So, I have an adjustable OPV on the way to install in my Starbucks Barista. I've put together a pressure gauge in a way that I can splice it in between the OPV and the boiler, which is downstream of the pump. It seemed that this was the easiest and less complicated way to measure pressure since all I had to do is hook up two ends of the PTFE teflon tube on either side of the retrofitted gauge with parts I could easily find. I only have a naked portafilter and the pressurized PF, so that portafilter pressure gauge wouldn't work. The steam wand is an odd size, so finding the correct size pressure/temperature tubing was difficult. So, my question is: Is this an accurate way to measure and adjust pressure as I pull a shot?

Here is the OPV:

For the record, and anyone interested who owns a *$ Barista or similar, here is the process I went through to make this OPV work.

As I mentioned above, I bought that pictured Expobar OPV from Parts Guru. It was the only one listed as compatible with my machine, so I went ahead and ordered it. They also sell a "kit" with an "adapter", which is just a barb fitting to slip the teflon hose on to for an additional $15! I figured I could just pick up a barb fitting at a hardware store for 50 cents. Upon receiving it, it also had metric threading just like the rest of the internals of the machine. And naturally, here in the U.S., metric anything is hard to come by, and I'm getting online-ordering-fatigue already. I originally thought that I'd insert a gauge in between the newly installed OPV and boiler, but that meant splicing the teflon tube of metric size. So instead, I gutted the old non-adjustable OPV to use as a tee, with the gauge coming off the 6mm barbed outlet side with 5/16 teflon tube.


After the gauge is a ball valve to release air out the end so there is only water left.


Now, with the new OPV and the old OPV serving as the tee, I had less space to work with. The pump/OPV/old OPV now needed to be mounted further from the inner wall. Thankfully there's another set of mounting holes to accommodate (strange how they thought about that) the new set up. But it still rattles against the wall, so I've ordered some sorbothane bushings for serious vibration dampening.




The nice thing about this particular adjustable OPV is that it enabled me to adjust the pressure while pulling a shot! I've seen others that require removing the outlet barb fitting in order to adjust. This made adjustment extremely easy and fast. I've got it dialed in at approximately 9 bar now, though the needle fluttered between 8 and 10 bar during the shot, so I split the difference. After I was finished, I removed the valve and gauge, trimmed back the tube coming out of the outlet, re-inserted the barb fitting and capped that off. This will be sort of a service hose when I want to re-measure pressure. The shorter hose fits nicely tucked in when I replace the back panel.

do you have the parts list for this mod? i have the same machine and wanting to get a consistent brew pressure from the stock one.