Final answer:
1) 1. The vent system should be designed to prevent a trap seal from being exposed to a pressure differential of more than 1 inch of a water column to protect the integrity of the trap.
Step-by-step explanation:
The question pertains to the design specifications of a vent system in plumbing to ensure that a trap seal maintains its integrity by not being exposed to pressure differentials that could cause the seal to break. Regarding the given options for the maximum allowable pressure differential on the outlet side of the trap, the correct value would typically adhere to local plumbing codes, which often specify that the vent system should be designed to prevent a trap seal from being exposed to a pressure differential of more than 1 inch of water column. This ensures that the trap remains effective in preventing gases from entering the living spaces from the drainage system.
In more technical terms, a proper vent system ensures that the air pressure in the drainage system is equalized, protecting the water seals in traps from being siphoned or blown by preventing the creation of negative or positive pressure differentials that exceed safe limits.