Underground Couplers, Adaptors & Reducers
The connecting and transition fittings for buried drainage — joining pipe to pipe, stepping between sizes, and making the change between PVC-U and the clay or cast iron already in the ground.
Also searched as: slip coupler, drain coupler, clay adaptor, cast iron adaptor, drain reducer, transition fitting
Slip couplers
A slip coupler has no internal register, so it slides fully onto one pipe and back over the joint. It is the fitting used to cut a new branch or a repair section into an existing run where neither end can be moved. Two slip couplers and two short pipe lengths are the standard repair assembly.
Adaptors to other materials
Buried drainage in the UAE frequently connects to existing clayware or cast iron. Purpose-made adaptors give a proper sealed transition rather than a mortared joint, which is where most infiltration and root ingress problems begin.
Soil-to-drain transition
Where the above-ground stack meets the buried drain, use the correct adaptor between the BS EN 1329 grey system and the BS EN 1401 brown system. The two are not interchangeable and a forced joint between them will leak.