Hi guys,

I'm sort of in the middle of putting together a small espresso machine and it was suggested to me by a HB member (pdx) that it might be a good idea to get rid of the 3-way valve and add another tube from the group to create a 'exhaust' for the pressure purge after a finished shot. This does sound good, but I was curious if anyone ever used a machine like this? I was planning to use two 2-way solenoid valves instead of the 3-way valve, put one on the group supply line and one on the 'exhaust' line. The only problem, I see here is that the 2-way valve will have to be connected with a bit of tubing which might affect thermal stability. I was looking for something that looks like the 3-way (size-wise and how it fits under the group), only in 2-way version, but couldn't really find anything. A double 2-way interchanging valve might be a good idea, but I'm guessing they are a bit large and might not fit easily.

Btw anyone knows what non 3 way machines use to block the line between the boiler and the group? I'm guessing there's has to be something there otherwise when switched to steam-mode, water and steam would escape through the group.

Regards,
dsc.

dsc wrote:Btw anyone knows what non 3 way machines use to block the line between the boiler and the group? I'm guessing there's has to be something there otherwise when switched to steam-mode, water and steam would escape through the group.

You don't need a three way valve to block the line between boiler and group. Machines without a three-way valve such as the Pavoni lever do not depressurize the group, alas the infamous portafilter sneeze?

I believe the little Gaggias just use a check valve between the boiler and the group that's set somewhere around 2-4 bar, high enough to keep steam in, but let brewing water out. It's a simple solution, and very efficient in terms of mechanicals and packaging, but I don't know if it's ideal in terms of pressure (or pressure profile).

Hi guys,

yeah I know I don't need the 3-way valve, and I will add a separate tube to get rid of excess pressure, but I will need to somehow block the way back to the boiler, otherwise all the crap from above the puck might go reverse and it will end pretty badly. I can use a simple 2 way valve (or a check valve), just below the group, but that complicates the whole setup and lowers thermal stability.

Regards,
dsc.