Just for fun let’s calculate it. Houston treats 449 million gallons per day. 449 divided by 24 is 18.7 million gallons per hour. Divided by 60 minutes in an hour is 0.3 million gallons per minute which is 300,000 gallons per minute. An average bathtub is 42 gallons. 42 x 500,000 = 21 million gallons. 21,000,000 gallons divide by 300,000 gallons per minute is 70 minutes so yes, it would have to be a slow trickle to fill a normal bathtub in 70 minutes.
I do recall back in the day that they could estimate how many people might be watching a movie on TV judging by the water pressure drop during a commercial.
Like they say up here, to keep from getting attacked by a grizzly bear you don’t have to outrun the bear. You just have to outrun your buddy.