Hi, I am Dr. Peter and would like to help.
1- How long has he been drinking lots of water?
2- Is he losing weight?
3- Is his appetite the same, less or more?
1. He has been drinking a lot of water for a 4-6 weeks.
2. He has been losing weight over the past several years a lb or two a year His original weight was 17 lbs.
3 His appetite is the same
When a cat starts drinking more then normal, it is usually a sign of either kidney disease, diabetes, infections, cancer, etc. The excess amount of water is what causes the vomiting, now, there is an underlying illness causing him to drink more. You need to have him checked by your vet and have a blood test done to rule in or rule out any of the above conditions. All of these conditions are treatable, the earlier we get to them the better the prognosis. Consider an appointment with your day vet soon.