DIY CO2 can not be shut off. My mom has a cautionary story from her college days when she made homemade root beer. For those not in the know, root beer and other homemade sodas can be made with yeast, not just compressed CO2. Anyway, she heard a bang, and then another bang, and eventually discovered that the racket was coming from the closet where she'd stored: a. root beer b. linens. This stuff was in recycled glass soda bottles. I suspect that plastic will burst at even lower pressures.
The point is, you can't shut off DIY CO2. You can bleed some of the pressure or you can disconnect it for the night, but why bother?