CFR /  Title 46  /  Part 174  /  Sec. 174.325 Equalization.

When doing the calculations required by Sec. 174.310 of this subpart--

(a) Equalization arrangements requiring mechanical aids, such as valves, may not be assumed to be effective in reducing the angle of heel; and

(b) Spaces joined by ducts may be assumed to be common spaces only if equalization takes place within 15 minutes after flooding begins.