There is an older topic on this, but i didn't see a resolution.

On the Duetto there appears to be a safety OPV that routes to the drip tray. (it's a vertical brass mass between the 2 boilers). Mine seems to drip on warmup and on cool down. My machine is plumbed in, and when the machine is off and the lever up i have about 2.75 bar of pressure on my gauge, when the lever is down (blocking flow) my line pressure reads about 3.25bar.
It appears when i turn off the water supply, the drip stops.

Is this normal behavior (the dripping when plumbed in)? I don't think it is.
It may or may not drip when everything is heated up. I'll try to pay attention tomorrow.

Do i need to somehow access the OPV to clean it? Replace it entirely? Leave it alone?

any help appreciated.

I can confirm the dripping is even when the machine is hot. Basically if it's under line pressure from the plumbing, there is a dripping. About 1 drop every 10-20 seconds

You can post photos to be certain, but it sounds like you're referring to the expansion valve. For espresso machines with rotary pumps, they serve the purpose of protecting the hydraulic system from excessive pressure during the brew boiler (re)heating. They typically are set to open at ~12 bar. If it's dripping at 2.75 bar, water would flow quickly at brew pressure. Assuming it does not, my guess is that some scale is preventing it from sealing properly.

Thanks Dan, picture is below. The "item" that is dripping into the drip tray.
It's the thing between the boilers, in vertical position, with a hex nut visible.



Water debit with no pf is 200g water in 20 seconds, that's at 8 bar with no restriction. My brew pressure is 8.5-9 bar.

Is there any way to clean this or does it have to be replaced?

That OPV (typically set to 11-12 bar) for your machine looks very similar, if not identical, to the OPV used on earlier model Quick Mill machines. Parts are readily available from Chris Coffee and don't forget to ask for the o-ring for the adjuster.

Looks pretty accessible from the bottom and don't forget to shut off the water and relieve any residual pressure. Have paper towels handy.

thanks Eric. Sounds like i just need to replace. I'll give Chris coffee a call.
As far as access i'll have to look.

thanks

Just spoke to a tech at Chris' Coffee, and he gave me the part number for the gasket that has likely dry rotted or worn.
For future reference and others, mine is the "old style" expansion valve on a duetto II, and the gasket part number is 8F194V

He suggested a unscrew the line from both boilers and lift the whole tube section with the expansion valve on it out, open it up, replace gasket and then reassemble setting the adjustment screw to "about where it was before".

Seems simple enough.

thanks everyone!

EDIT: Per Eric's recommendation I also bought the o-ring, part 8F888. Not sure if needed, but i figured i'm paying $8 shipping might as well get the $1.50 part too.