Assertion: plumbing fixture's drain | /r/CapableOf | prevent positive air pressure
Facets:
value: further
type: MANNER
value: in the sewer
type: LOCATION
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.