Apipe is leaking out 1.5 cups per day about how many gallons per week is a pipe leaking

The pipe is leaking 0.65625 gallons a week

There's 16 cups in a gallon.
1.5*7 = 10.5 cups 
10.5/16 = 0.65625

There are 16 cups in a gallon. 
If the pipe is leaking 1.5 cups every day, that is only 10.5 cups. 
10.5 cups of water do not get you to a gallon.
But, if you want to see how many gallons there would be in two weeks, that would be 21 cups which is equivalent to 1 gallon and 4 cups. 
Hope this helps!