Absolutely NOT! It is very unsanitary for the poor dogs. Why not simply keep the toilet seat down at all times? My cat tried that, and that was the first and last time any toilet seat was left up in our household. Discourage your pets from drinking from a toilet, no matter how clean it is, it is still always full of harmful human parasites, bacteria and viruses that can sicken the pet. Change your pet's water daily, and your pet will be happy to drink from its own bowl, not a toilet bowl.