Code of Federal Regulations Title 46. Shipping § 46.154.1305 Liquid level gauging system:  Standards

(a) Each cargo tank must have at least one liquid level gauging system that is operable:

(b) Unless the cargo tank has one liquid gauging system that can be repaired and maintained when the tank contains cargo, each cargo tank must have at least two liquid level gauging systems that meet paragraph (a) of this section.

(c) Each liquid level gauging system must measure liquid levels from 400 mm (16 in.) or less from the lowest point in the cargo tank, except collection wells, to 100 percent full.