What causes sudden excessive drooling in cats?

I have a 14 month old male (fixed) cat. He is generally pretty healthy besides having asthma. This morning i woke up to find little puddles around my house and after ruling out a leaky roof i chalked it up to my cat playing in his water dish. When i came home for lunch, i noticed that he is drooling very, very badly, it's literally a steady drip out of his mouth, and their are small puddles of drool ALL over my house. He was very docile which is unlike him when i usually come home for lunch as well. Im not to sure what could be wrong. Could this be something serious enough that i should take him in? I would like to avoid the vet if i can..