Assertion: plumbing fixture's drain | /r/HasProperty | vented positive air pressure
Facets:
value: in the sewer
type: LOCATION
value: to maintain the water seal
type: PURPOSE
Source sentences:
text: Almost each plumbing fixture's drain must be vented to maintain the water seal from drying up due to negative air pressure in the drain, and further prevent positive air pressure in the sewer from pushing gases past the water seal.