The home knockbox may be small but it can comfortably hold 10 double pucks of coffee before it needs emptying. To empty just lift the rubber bar out and discard the coffee as you wish. A silicon ring on the bottom prevents it moving about the place and also helps to reduce the noise.
To wash we recommend you just give it a rinse in mild detergent. The plastic tub is dishwasher safe but we are not sure you need to go that far as a mild rinse works every time.