21 CFR § 112.133 - What requirements apply to plumbing?
The plumbing must be of an adequate size and design and be adequately installed and maintained to:
(a) Distribute water under pressure as needed, in sufficient quantities, in all areas where used for covered activities, for sanitary operations, or for hand-washing and toilet facilities;
(b) Properly convey sewage and liquid disposable waste;
(d) Not allow backflow from, or cross connection between, piping systems that discharge waste water or sewage and piping systems that carry water used for a covered activity, for sanitary operations, or for use in hand-washing facilities.