Definition(s)
25% (50%) Drainage Time
25% (50%) drainage time is the time for 25% (50%) of the liquid content of a foam to drain out.
Source: IMO MSC.1/Circ.1312, Revised Guidelines for the performance and testing criteria, and surveys of foam concentrates for fixed fire-extinguishing systems, 10 June 2009, International Maritime Organization. Regulatory Guidance