14 CFR § 25.1455
Draining of fluids subject to freezing
July 13, 2020
If fluids subject to freezing may be drained overboard in flight or during ground operation, the drains must be designed and located to prevent the formation of hazardous quantities of ice on the airplane as a result of the drainage.
[Amdt. 25-23, 35 FR 5680, Apr. 8, 1970]