Final answer:
An Excess flow valve permits a plastic pipe to terminate above grade. It restricts the flow of fluids when they exceed a preset limit. An Indicator, elbow, and expansion joint do not specifically allow for such termination.
Step-by-step explanation:
In the context of plumbing and engineering, a plastic pipe can be permitted to terminate above grade when an Excess flow valve is used. The excess flow valve is designed to stop or restrict the flow of gas, air, or water through the pipe if the flow rate exceeds a preset limit. Contrary to the options provided, neither an Indicator, elbow nor expansion joint particularly allow for the termination of a plastic pipe above grade as these components serve different functions in a pipeline system.
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