Controller for Nespresso Autofill

I created an autofill setup for my Nespresso machine using an electrical sensor and a solenoid to control water flow.

Predictably, this setup stutters badly when filling. I need to decouple the sensor and the solenoid.

I would welcome any comment on the following.

I've mocked up this circuit (haven't built it yet: waiting on components) hoping that it will cause a long delay on start and a short delay on stop.

The sensor is closed when water level is normal, open when it drops. I'm hoping for about a 20 second delay on start and a 4 second delay on stop.

I'll appreciate any suggestions relating to design or values.