My greyhound Woody was experiencing the same issues - drinking excessively, diluted urine. Woody would lay next to the water bowl and drink, drink, drink. We spent so much time trying to distract him/stop him from drinking water. It was upsetting to all of us. His water drinking was non-stop it disrupted his sleep and ours. No one in the house were happy campers. Labwork/ultrasound/urinalysis showed nothing obvious...everything in normal ranges. With the exception of the non-concentrated urine. We ruled out renal disease, Cushings, tumours, etc., etc. My vet suggested trying the ADH (anti diuretic hormone) eyedrops rather than submitting him to further stressful testing (Woody is 14). The vet said we would know within 1-2 doses if it was what he needed..wouldn't hurt him if he didn't have water diabetes (diabetes insipidus). Well, the drops worked and he's been on them for over 6 months now. The medication made the diagnosis...Woody has water diabetes (diabetes insipidus).