clynch wrote:Could somebody explain to a noob what a blind filter is? I'd like the check the opv on a Breville that was purchased in November. Thanks.
blind filter is a basket with no holes in it, commonly used for backflushing.
It completely closes off the water path - the pump pumps against the blind filter and no water gets through.
If the machine doesn't have a 3-way valve, then after you turn the pump off, the portafilter will be pressurized with this water, and when you remove the portafilter from the group, you'll get a sneeze of hot water all over the place.
If the machine has a 3-way valve, then when the pump is turned off, the 3-way valve relieves this pressure (and water) to the drip tray.
For example:
http://www.espressoparts.com/F_156



