###Human: John has a very inefficient toilet that uses 5 gallons of water per flush and his household flushed 15 times per day.  He replaced it with a toilet that uses 80% less water per flush.  How much water did John save in June?, ### Assistant: He used to use 5*15=75 gallons of water per day.
This means he used 75*30=2250 gallons a month.
His new toilet uses 5*.8=4 gallons less water per flush.
So, it only uses 5-4=1 gallon per flush.
That means he uses 1*15=15 gallons per day.
All in all, it accounts for a total usage of 15*30=450 gallons.
So, he saved 2250-450=1800 gallons per month. 
 So the answer is :  1800