From The Boiler Room...
I have a 2003 Salvatore automatic espresso machine with the E61 brew group that is an awesome machine. However, it lacks an overpressure valve (OPV), so it is not possible to control the brew pressure - which I measured to be 16 bar, well above the 9-10 bar range generally recommended for optimum extractions. My bean roasting and espresso brewing journey started recently in the Fall of 2012 thanks to a good friend of mine, Rick. We are an engineer and physicist on an eternal quest for that somewhat elusive, perfect shot of espresso.

I have access to a loaned Nuova Simonelli MAC 2000V with a rotary pump with an easy brew pressure adjustment that I've optimized so that the machine is producing some really awesome shots. With the goal of doing the same on the far less expensive Salvatore, I decided to add an OPV to the machine in my shop, "The Boiler Room", and am posting a description of the project with some pictures and a video for anyone who wants to learn how easy it is to do this. This modification is relatively inexpensive, easy to do with a few simple tools and takes just a few hours to complete (even for a couple of overly analytical guys hampered with physics and engineering degrees). And best of all, my Salvatore is now producing beautiful 30 sec extractions that it couldn't before.

Here is a video of the project: Parts List:
Total Cost: $46.45
1) Expansion Valve (overpressure valve, OPV)
From: ChrisCoffee.com
Product Code: EV321
Cost: $32.95

2) ¼ " OD x ⅛ " FIP Brass Connector
From local hardware.
Used to convert from ⅛ " MIP on OPV to ¼ " copper tubing using compression seal
Cost: $2.50

3) Brass Tee for ¼" copper tubing (compression seals)
From local hardware.
Cost: $5.00

4) ¼" copper tubing (about one foot)
From local hardware.
Cost: $2.00

5) ⅜ " Plastic tubing (about one foot)
From local hardware.
Cost: $1.00

6) Plastic elbow, ⅜ " tube to ¼ " thread
From local hardware.
Used to connect OPV over pressure flow to water reservoir
Cost: $3.00

7) 8 FTE hours
2 people for 4 hours
We could have done this in half the time, but we were having fun, drinking coffee and making trips to the hardware store.

Here is a picture of the Salvatore Espresso Machine:


Side view of the OPV install location before:


Top view of the OPV install location before:


Here is a side view of the tube to be removed:


Here is a top view of the tube to be removed:


Layout of the OPV install components:


Side view after the OPV install:


Top view of the OPV install:


OPV return water goes back into the reservoir:


Finished Product:


10 bar pressure at the brew head:

Nice job!

It is amazing how the internet can connect similar minded and situated people:
My son and I are both engineers (he a surgeon and me a lawyer in addition to our tech degrees), we both have Salvatore semi-automatic machines and we both were wondering how to add an OPV to limit the pressure on the SILKA pump. After finding your post yesterday, we both ordered OPVs from Chris Coffee and will install them. We are also considering taking the process a step further by installing some sort of quarter turn valve in series with the grouphead to enable changes to the brew pressure (like the high end machines) for pre-infusion and experimentation. This would not be possible w/o the OPV because the pump pressure would change as the flow was restricted.

Do you have any suggestion for a valve to use? It would be nice to have a side mounted lever to control this since there is no room elsewhere.

By the way, in case anyone is interested, for plumbed in machines, simply rout the OPV output to the drip tray rather than the reservoir.

We are an engineer and physicist on an eternal quest for that somewhat elusive, perfect shot of espresso.

Oh no, not again

That was a nice write-up and video.

One thing I would suggest is to use silicone hose from the OPV back to the reservoir . . . it gets a little hot under that hood. You can also sorta simulate a real brew by introducing a little leakage from the PF gage setup by not sealing 100%.

Very nice indeed, but I have four years left on my warranty. I am pretty sure they would void it despite the fact that if done properly could not hurt the machine.

For pre-infusion and variable pressure during brew on machines with a vibratory pump, consider adding a variac. But if you want a simple constant pressure, you can't beat an OPV.

Could you please explain what you mean. A Variac is a voltage regulator.

ripcityman wrote:Could you please explain what you mean. A Variac is a voltage regulator.

You can vary the the water pressure created by the vibratory pump by varying the voltage sent to the pump. Some Gaggia owners have installed this mod with success.

> You can vary the the water pressure created by the vibratory pump by varying the voltage sent to the pump. Some Gaggia owners have installed this mod with success.<

Interesting approach. Now I've got to research how the vibratory pump works: on voltage or cycles? What effect does reducing the lines VAC from 110 to, say, 90 Volts have on the force with which the solenoid fires? Or does reducing the voltage affect the speed at which that little bugger fires and rebounds?

Anyway, anyone thinking of doing this needs to open the box and figure out how to put the voltage control device in the circuit line to the pump. You cannot just plug your machine into the voltage control device.

I use voltage control for my vibratory pump and it works well to reduce pressure/flow. Frequency stays the same, force and stroke length decrease. I disconnected the pump from the normal switched power and fed it directly.

Others have used devices that either skip cycles or parts of cycles (like dimmers). This latter approach seems to have more mixed reviews.

Note that a variac also allows you to increase voltage - I don't recommend doing that.