Question: what does the air gap do on a dishwasher
[{'answer': 'backflow prevention', 'provenance': [{'wikipedia_id': '2331351', 'title': 'Air gap (plumbing)', 'start_paragraph_id': 2, 'start_character': 409, 'end_paragraph_id': 2, 'end_character': 428, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'prevents drain water from the sink from backing up into the dishwasher , possibly contaminating dishes'}, {'provenance': [{'wikipedia_id': '2331351', 'title': 'Air gap (plumbing)', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 728, 'bleu_score': 0.8878208331006621, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12577849189005082230}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '2331351', 'title': 'Air gap (plumbing)', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 428, 'bleu_score': 0.974188104609039, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12577849189005082230}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '2331351', 'title': 'Air gap (plumbing)', 'section': 'Section::::Abstract.', 'start_paragraph_id': 2, 'end_paragraph_id': 2, 'meta': {'evidence_span': ['A simple example is the space between a wall mounted faucet and the sink rim (this space is the air gap). Water can easily flow from the faucet into the sink, but there is no way that water can flow from the sink into the faucet without modifying the system. This arrangement will prevent any contaminants in the sink from flowing into the potable water system by siphonage and is the least expensive form of backflow prevention.', 'A simple example is the space between a wall mounted faucet and the sink rim (this space is the air gap). Water can easily flow from the faucet into the sink, but there is no way that water can flow from the sink into the faucet without modifying the system. This arrangement will prevent any contaminants in the sink from flowing into the potable water system by siphonage and is the least expensive form of backflow prevention.', 'backflow prevention']}}]}]