winsonlin Can I ask the following questions about ACS EVO LEVA V2?
Will the pressure relief system allow coffee liquid to flow back, causing the brewing head to need frequent cleaning?
Hope someone can answer me, thank you!
No, it doesn’t work in the same way as an E61 group or Ring group, or any of those variants.
E61 groups vent by opening the port to the vent area, this causes a sudden and dramatic and complete drop in pressure from 150 psi to 0. This causes water to rapidly leave the high pressure environment to the low pressure environment outside. It travels up from the coffee, pulling dirty coffee water and bits of coffee with it:
- up the shower screen
- bathes and through the dispersion disk
- into the cam chamber
- down through the preinfusion chamber and out the vent system
During this journey it deposits some whatever it has in it into those areas and that build up over time making backflushing necessary.
The process with the Evo lever is somewhat different. When the venting solenoid opens, it causes a sudden and large (not dramatic) drop in pressure because there is only an approx 2mm hole for fluid to flow through. This causes clean water from within the group cylinder, still under pressure from the descending piston to exit via the vent solenoid rather than through the group. The coffee puck acts as a relatively impermeable thing. The following does NOT happen to dirty coffee water as the coffee puck still sees some residual pressure as the piston is expelling water out of the vent solenoid.
- up the shower screen
- bathes and through the dispersion disk
- into the cam chamber (no cam chamber)
- out the vent system
Of course there might be a very tiny amount that goes back but it’s very small and just lightly stains water. This means that backflushing with cleaner would only need to be done once or twice per annum. I need to describe the process in a user tips document, which I plan to start writing at the weekend.
Of course you still need t remove and clean the shower screen, on an E61 you would do this every 3 days to 1 week ideally. On a lever you can do it every couple of weeks.