SOS from Paris

Our daughter called yesterday from Paris. (Such is Amanda's life that last Saturday she was in Sedona and this Saturday she's in Paris.)
As was often the case when I talk to my children my first words were, "What's wrong?''
She'd forgotten to turn the water on for the cats.
This seemed an odd thing to call me about since I'm in Phoenix, the cats are in London and she was in Paris. I didn't have keys to her apartment nor did I know anyone who did.
"How long can cats go without water?"
Ah, she was calling Dex.
Or rather the one person she knew who had a computer or the phone number for a vet who could give her the answer to that question.
"I need to know if I should get on a train now or if they'll be ok until we get back Sunday.''
Her cats are in the habit of jumping into the bathroom sink or, preferably, the bathtub and sipping water from the trickle she lets run from the faucet.
She'd forgotten, in her haste to leave for work Friday morning and her jet laggy state, to follow the faucet routine.
Michael, who is vigilant about such things, was already in Paris with his mother.
I told her I was on it and would call our vet and call her right back. Meanwhile, in my attempt to deepen my shallow knowledge of feline hydration, I googled "How many days can a cat go without water" and found that there are many people asking this question. One post was months ago and no one had answered.
The answers from the Google search weren't nearly as helpful as my vet tech's. (If they lose 10 to 14 percent of their weight in water, it could be fatal. If you can weigh them and do the math presumably you can fill their water dish.)
The vet tech said they'd be fine.
I called Amanda. She was relieved and headed into a restaurant.
I'll call tomorrow to see how they (the cats) survived.
Meanwhile, if you or your loved ones should run into a dehydrated cat, be sure not to over-water them. This can induce vomiting which sort of exacerbates the dehydration problem. Give them sips (obviously take them to a vet if you can verify that weight loss thing) and Pedialyte is recommended for the same reasons we give it to babies who are deydrated. The electrolytes, etc.
From what I gather from my quick Google search canine dehydration is another matter and at this point I admit extreme shallow knowledge on that topic other than as a precaution if you are going to be gone again: Leave several bowls of water.