Tell him/her to take th ebunny to the rabbit savvy vet.   No experienced vet is going to tell someone that a bunny drinks a lot of water out of boredom without checking obvious illness problems first.  Offer this link about how to find a good rabbit savvy vet.  http://www.rabbit.org/faq/sections/vet.html

 The bunny could have a UTI or some other illness. 

Also, let him know that white vinegar helps clear out the scent from the box.  Yes it smells like vinegar, but that goes away.    Of course the vinegar has to be rinsed first before litter is put back in the box.

The bunny also might need it’s scent glands looked at and cleaned. 

So ultimately, this person needs to find a vet with more experience with rabbits.

I wonder if this has been going on the whole time or if this recently changed.

HAHA moobunnay I saw that post too but declined answering since I know all the Bunny Bunch rescuers comb cl for bunny posts and figured they would respond. You might refer that person to these forums btw. Personally with the experience I’ve had with my hamster having concentrated urine, this is usually a kidney or diabetic problem and may be helped by changing diet. If that does not help, and the animal is constantly dehydrated, I recommend giving only flavorless Glacieau water (has electrolytes and no sugar) to keep them hydrated. It is sold in normal grocery stores. But yes, this person needs to go to a rabbit savvy vet.