1,047,500. Junction pieces. B. DEEBLE and BELLS BROS. (MANCHESTER) Ltd. Dec. 1, 1965 [Dec. 2, 1964], No. 48922/64. Heading F2G. [Also in Division B1] Filtrate is withdrawn from the bottom of a filter bed of sand or gravel by a drainage system built up of separate tubular T-pieces 10, each having one or two socket(s) 12, 14 and two or one spigot end(s) 13 and liquid entry apertures. T-pieces 10 may be metal or moulded plastics and may screw together or be smooth ended and joined by adhesive or H.F. welding. Figs. 5-9, not shown, illustrated how T- pieces 10 are arranged to cover round and rectangular areas on the supporting floors of filter beds in upright and horizontal cylindrical tanks. T-pieces 10 have downwardly extending integral feet (15), and in Figs. 1-3, not shown, the liquid entry apertures comprise narrow, part-circumferential, downwardly facing slots (16). A similar, upwardly facing air vent 17 is also provided. In Figs. 10-12, not shown, the liquid entry apertures comprise upwardly extending bodies (47) carrying strainers (46), constructed of alternate annulii (53) and cruciform spacers (54) in the manner of an edge filter. A bolt (51) may attach the strainer assembly (46) to the body (47) or attach both assembly and body (47) to the T-piece. In Fig. 13, not shown, the liquid entry aperture comprises a simpler upwardly extending nozzle (59) with radial inlet holes (61). Body (47) in Figs. 10, 11 could be integral with the T-piece. When the T-pieces are joined to form a drainage network, open sockets or spigots 12, 13, 14 are closed by plugs. The filter bed could be graded gravel, with large pebbles at the bottom. When used to filter swimming-bath water, the return flow to the bath may be warmed, chlorinated or sterilized.