How long is it safe to allow a dog to go without drinking?

From: Paul And Mavis with dog Jerry
Breed: Mix

Pet Symptoms:
How long is it safe to allow a dog to go without drinking? Began treatment yesterday for vestibular syndrome

Tried:
Syringing water into his mouth
Our Advice:
If it is just vestibular disease the dog should get better soon. Continue syringe feeding/drinking the dog and if he is no better take him to the vets again tomorrow. If he is refusing to take water/food with syringe contact the emergency vets and they will put him on a drip.