NRS 484D.275
Reservoirs.
1.
Every bus, truck or truck-tractor with air-operated brakes shall be equipped with at least one reservoir sufficient to insure that, when fully charged to the maximum pressure as regulated by the air compressor governor cutout setting, a full service brake application may be made without lowering such reservoir pressure by more than 30 percent. Each reservoir shall be provided with means for readily draining accumulated oil or water.2.
Every truck with three or more axles equipped with vacuum-assistor type brakes and every truck-tractor and truck used for towing a vehicle equipped with vacuum brakes shall be equipped with a reserve capacity or a vacuum reservoir sufficient to insure that, with the reserve capacity or reservoir fully charged and with the engine stopped, a full service brake application may be made without depleting the vacuum supply by more than 30 percent.3.
All motor vehicles, trailers, semitrailers and pole trailers, when equipped with air or vacuum reservoirs or reserve capacity as required by this section, shall have such reservoirs or reserve capacity so safeguarded by a check valve or equivalent device that in the event of failure or leakage in its connection to the source of compressed air or vacuum, the stored air or vacuum shall not be depleted by the leak or failure.
Source:
Section 484D.275 — Reservoirs., https://www.leg.state.nv.us/NRS/NRS-484D.html#NRS484DSec275.