My 120 lbs Chocolate Labrador keeps throwing up after he drinks water. What could it be?

Obesity!

If its not that then its Megaesophagus, megaesophagus is the most common cause of regurgitation.

My Akita had it.

Honestly at 120 pounds you won't be spending money at the vet much longer. Obesity will take years off a dogs life.
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I would get a second opinion.
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Just surrender him to a lab rescue.
Your dog doesn't deserve an owner that is just willing to give up on him. Never thought of getting a 2nd opinion from a different vet?
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First, don't give up on your dog.

Do you clean the bowl it drinks water from? Change it's diet, it could help. Or maybe there are worms inside it.
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Maybe you should ask a more advanced animal doctor. He doesn't sound like he is very helpful.
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I'm thinking worms too! but you said you went to the vet already….i don't know. Besides 120 pounds sounds too heavy mines weights 60 lbs. Yours is twice as much. How old is he?
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do you have city water or well water? mabe the kind of water it is is that is affecting him/her. you should give him bottled water if you can.
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You have made sure he isn't drinking too much, too quickly.

Limiting the amount he can get at one time so he doesn't gulp large amounts down which would cause to vomit it right back up would help if you haven't already. Maybe changing water to bottled or distilled - sometimes the chemicals in tap water will bother a few dogs systems.
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Hi, I also had a lab. Wonderful family dog & companion. She also would gulp water & then throw up. I found out that if I limited her water intake. she didn't throw up. Maybe this will help for you also, Kathy
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What's the frequency of the vomiting? Every time? Just recently?

Try raising the water dish so he doesn't have to get so low.

Only put a little water at a time in the bowl so he can't 'guzzle' it down. He may be swallowing a lot of air when he drinks heavily.

If you've done a food change recently he may have tummy trouble. It's always a good idea to gradually change any pet food by adding a little of the new to mostly old food and gradually increasing the new food and decreasing the old so that it isn't a jar to their system.
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First of all …….. what's his age ?! Anyway try to give him Anti-Gas related medicine ……. It won't do any harm to him ……. Also try to get the opinion of some other VET too in this regard …….. because the treatment of animals are said to be blind ones …… its like hit and trial …… so all the best ……. may he start to kick and rock ASAP ………
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