Question

Why oils and fas not be realeased on the drain

Answer 1

Oil and fats Cannot be realeaed in drain because as they are lighter than water so obviously they 'll float on water this forming a layer on the drain water's top ....this would led to pollution of the drain as mosquito will start to reproduce over it and some small scale of aquatic animal would get into danger due to the cut off supply of oxygen.
Hope this helps you dear :)
#Swara15 ;)

Answer 2

if oils and fats are released into drains then there will be accumulation of oils on water which will reduce the flowing of water speed if there will be less flow of water our drains will be stagnated  this will lead to mosquitoes spreading over that drain     
hope it helps you....