Keep your espresso machine's 3-way valve clean.
Backflushing your espresso machine is essential for fresh tasting coffee and maintaining the 3-way valve system. This rubber disc drops into the bottom of your double basket. It fits all home machines with a 3-way electro-valve system (3-way valve machines always have a drip-hose or other drainpipe which feeds into the drip tray).
Simplified backflush instructions: Using the blind filter replace the portafilter basket with the "blind filter". Put the group handle with the blind filter into the group head (just like you were going to brew a shot). Start a "coffee cycle " and let the pump run approximately 10 seconds; you will hear the pump noise change to a higher pitched sound. Now turn the pump off. Repeat this procedure 3 or 4 times. After the second cycle let the machine sit for about 5 to 20 minutes and let the cleaner do its work. Continue with the last two cycles.
When you remove the group handle, you will see all the coffee grounds that were "stuck up" on the gasket and shower. Repeat until the water is clear.