NFPA 22, 2018 Edition regarding filling requirement and duration -
Section 220.127.116.11. states "The water supply shall be capable of filling the minimum required fire protection volume within the tank in a maximum of 8 hours" and at the same time Section 14.4.3 states "The tank shall be kept filled, and the water level shall never be more than 4 in. (102 mm) below the designated fire service level."
If I understand correctly, as soon as the water goes below 4-inches from the normal filled level in the tank (HHL), the makeup water supply should be starting to replenish and the pipe sizes should be provided in such a way that the tank can be filled within 8-hours.
In a fire, as the water is going down, the tank will always start full.
What is the case where the tank would be emptied out (except maintenance) and need to be refilled within 8-hours?
What if we store water in two tanks to allow maintenance - would we not need to meet this 8-hour requirement?
I'm unsure of how these two requirements work together. Appreciate any feedback.
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