krislane:

When a new email message arrives, water is released into one of three tubes representing your work, family and friends. By controlling the valve on each tube, you can control how much communication you receive from each group. For example, you could completely shut off work after 5pm. The tube will still fill from any new messages but none of these messages will be passed on to your email in-box. You could later, perhaps the next morning, open the valve completely and the held messages will be passed through to your in-box.

/via Hardsketcher - Filippo Cuttica

Source: cargocollective.com