Clarity in Design

Recently I was at a family members house where they had recently remodeled their bathroom. It looks beautiful with new countertops, shower, and water-saving toilet.

On top of this toilet is a dual-flush set of buttons - one large and one small - clustered together like pictured below. You can push one, the other, or both simultaneously. 

dual flush buttons

I completely understand that one saves more water than the other, but I'm missing some kind of indication of what I should do. I have several questions for this flushing system:

  • Is the small button for after I just pee? Or is it smaller because I'll use it less often (a la going #2)?
  • Is the larger one for larger trips to the toilette? Or is it a larger target for the most common flushing reason (just urine)?
  • What does pushing both do? Should I just go ahead and get a mop and towels if I press both?

Without any kind of clarifying indication, I am unsure what will happen when I press these buttons, either individually or together. Perhaps a diagram is necessary for proper use?

dual flush buttons with diagram

Or even better, a simple full/half flush icon would suffice.

dual flush buttons with icons

(And while we're at it, can we standardize the sides? Maybe left for half flush, right for full flush.. always?)

When designing our interfaces for users unfamiliar with the functions of our designs, we must ensure that the sequence of events is clear enough for the user to take the correct action.

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