46 C.F.R. § 108.475 – Piping.

(a) Each pipe, valve, and fitting in a foam extinguishing system must meet the applicable requirements in Subchapter F of this chapter.
(b) Each pipe, valve, and fitting made of ferrous material must be protected inside and outside from corrosion.
(c) Each pipe, valve, and fitting must have support and protection from damage.
(d) Each foam extinguishing system must have enough—
1. (1) Dirt traps to prevent the accumulation of dirt in its pipes; and
2. (2) Drains to remove liquid from the system.
(e) Piping in a foam extinguishing system must be used only for discharging foam.