The silent flush

We have been having a problem with a young boy in our house not flushing. Not to name names, but someone isn't
flushing.

(William coming out of the bathroom)

Dad: William, did you flush?
William: uh huh, yep
Dad: are you sure? I didn't hear anything. Can you go and check?
William: you didn't hear it because it was a silent flush. The kind you CAN'T hear.

(Lots of muffled giggles)

Dad: I think the silent flush might not be doing the job. Might want to check again.
William: oh man. Ok dad.

(Flushing)
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