Pre infusion fitted... now back flush noise

[nod1]

Hi
i have recently bought and fitted the mechanical pre-infusion device which i think has come from Chris' coffee but i bought it from La Spaz in the UK. It was straightforward to fit and i now get 6 seconds before the espresso appears - all good. the issue is that now, i think on only some shots, i get a noise at the end of the extraction when i press the double cup button (to stop the extraction). it is the same noise you get when back flushing and am pretty sure it is water going down into the drip tray (? through the solenoid valve?)
is this normal or has something gone wrong during the fitting please
thanks

[rhinoevans]

Normal

[nod1]

Normal

excellent - thanks for the speedy response... does it happen without pre-infusion and i have not noticed before? or if not, why does it happen with pre-infusion

[rhinoevans]

I think it is just the back flush of the water. Added mine a year ago, not sure I can taste the difference in the cup, but I don't regret it.

[chas]

I agree with Rhinoevans that the sound is normal. That preinfusion device has a spring loaded cylinder inside. When you first start a shot, the water pressure pushes back that cylinder and it fills with a couple ounces of water. This greatly lowers the pressure on top of the puck so that you get good preinfusion.

When the shot shuts off and the 3-way valve opens, you not only get the normal water pressure release into the drip tray but the spring in that cylinder pushes out the extra two ounces very quickly and adds to the water flow out the 3-way valve.

[nod1]

Thanks a lot Chas... This is super helped and a great explanation. Much appreciated


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[nod1]

I think it is just the back flush of the water. Added mine a year ago, not sure I can taste the difference in the cup, but I don't regret it.

Thanks also... I have only had mine a week but I am not sure what difference I am noticing. What difference do you think it should have made? I'm going to post a question about making coffee after preinfusion...


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