Mod- manual OPV and brew pressure gauge.

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#1: Post by hbuchtel »

Its cool how many pressure-related posts have come up recently!

The idea for this mod came up in this post, the only real difference is that the "steam-valve" is now on the cold water side of the boiler which makes the temperature easier to control.

I added a oil-filled pressure gauge and a manual valve to a Precisia (single boiler w/ PID, vibe pump, no OPV) as you can see from the picture. I had trouble finding the right parts, the best I can say is that it doesn't leak . . . :roll:

This mod was easy, cheap, and has made my espresso much better. It could also be done on a HX machine. I'm not comfortable enough with my technique to do any 'research' with it, but others who are would be able to follow and contribute to threads like Greg Scace's pressure profiling one. If enough people do it we could get some Distributed Espresso Profiling action... :D

The Precisia doesn't have an OPV which was making for some very upsetting early mornings! This first video shows what happens when you combine a 15 bar pump, a tight grind, and poorly fitting PF gasket.
In the second video I held 9 bar* for 30 seconds. *not necessarily 9 bar at the top of the puck
In the third video I held 9 bar for 15 seconds and slowly reduced the pressure for the next 15.
This mod has made my cheap machine into one that I can trust, but on a better machine (with an OPV)... I think it could be really awesome!


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#2: Post by mfasano »


I am going to modify my Baby Gaggia with a pressure regulator. I purchased a Watts 26A range D regulator. it is the only food grade regulator I could find with the pressure range needed. I will put it between the OVP (over Pressure valve) and the boiler. I intend to adjust the OVP to give over 10.5 bar so there will be sufficent pressure behined the regulator to give 9.5 bar on the other side. I will let you know how it turns out.


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hbuchtel (original poster)

#3: Post by hbuchtel (original poster) »

Nice find! Can you post a link or picture to the model you bought?

The position sounds right. Do you have the right adapters for the plumbing?

Regards, Henry


#4: Post by mfasano »

I went to the Watts web site and found a local distributor and I phoned the order ~$80 w/ shipping. It does not come with a handle. I got the one with 1/4" NPT threads.

I do not have the fittings yet. My Baby Gaggia uses plastic tubing and compression fittings. I can get the fittings at any hardware store but I don't know about tubing that can handle the pressure. I may use copper tubing.