"As far as the aftermath goes, a big-city hotel is actually a pretty good survival shelter: solid concrete and steel construction, wide stairways, and plenty of sleeping space. Water is readily available in a hotel:
every toilet in the building will have 1-3 gallons of clean, drinkable water in its tank, and then there are the big hot water heater tanks and indoor swimming pools that can be drained. The toilets won't flush
anymore of course, but human waste can be disposed of by simply throwing it off a balcony."
The toilets will flush just fine if you pour some water in the tank. Flood or salt water preferably, but it'll get rid of the waste.
Not when all the sewer lines are full of water and flowing nowhere.