I have a toilet with a Fluidmaster 400A fill valve (installed
by a plumber). It has (apparently) always had this
problem: The refill flow rate is too high. The bowl
fills and the refill flow keeps going and (apparently)
water goes over the "hump" in the trap and down the
drain. The water pressure here is not high. It seems
to me that too much water is coming out of the refill
tube and not enough is coming out elsewhere (wherever
that might be). Can this be adjusted?

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