my cats rarely if ever drank water, and eventually it led to one of them becoming very sick and needing two surgeries. he had kidney stones and a blockage of crystals in his urinary tract...what a mess. a friend had a similar issue with her boy cat and it took three surgeries to finally reverse the damage...and he went from being Oliver to Olive in the process
among the changes i made after Frodo's illness (he made a full recovery, thank goodness) was buying a water fountain for the cats. i have seen super expensive ones everywhere, but the one i bought came from Homegoods and cost about $20. and they LOVE it. i went from never, ever seeing them drink water to watching them lap it up all the time.
i know you started this thread to talk about Zaphod's poo breath (

) but if by chance you're looking for a solution that doesn't include toilet bowls or your own water glass, maybe start keeping an eye out for a reasonably priced cat water fountain? the one i bought is made by Animal Planet (or at least, they licensed the AP name) and i've seen it online for about $25.