Instruct: Classify the following sentence into a predefined topic category:
On an reverse osmosis water system do you always have to use PVC pipe? Can copper be used? If not why? BSK.?
Assign it to one of the following topics:[Society & Culture, Science & Mathematics, Health, Education & Reference, Computers & Internet, Sports, Business & Finance, Entertainment & Music, Family & Relationships, Politics & Government]
Output: