In the example above, the speaker asks whether her son turned the faucet "all the way off". The phrase "all the way ___" is used to talk about doing something completely:

I walked all the way up the stairs, then all the way back down again.

Take it all the way off.

It's freezing in here! Let's turn the heat all the way up.

Empty the cans all the way out. Don't miss anything!