I forgot to answer your original question, Is he dehydrated. Any chameleon that drinks for five minutes sounds pretty dehydrated to me. I never see my animals drink unless there is something wrong or they have just laid a clutch of eggs.
Can you post pictures of your chameleon--his eyes, back and pelvis area? A dehydrated chameleon will look skinny and have a dry look to their skin. Urates are only one way to judge hydration. I look a the body condition of the animal which shows dehydration immediately, not many hours or days later when they finally have pass stool. A dehydrated chameleon does not always have yellow/orange urates.