Demountable Coupling Body. Why Use a Demountable Coupling?. For example: A 50mm Demountable Coupling fits 50mm OD rigid pipe. 110mm (4" Waste). Once installed, align the male (coupling body) and female (retaining nut) threads, tighten them together, and the heavy-duty E.D.P.M sealing washer creates a strong, water-tight seal.
eBay