Spurs run to Coppermills Water Treatment Works near Walthamstow, and to the reservoir and pumping station at Honor Oak.

The ring main extended the operational life of the high-level trunks by reducing the demand placed on them, and, by providing an increased level of redundancy, enabled them to be more easily isolated and maintained.

A tunnel was also built between Coppermills Water Treatment Works and Stoke Newington at the same time, although this was not connected to the rest of the ring until the later extension phase.

These were positioned to deliver water to the areas of London with the greatest demand, which often meant they had to be constructed in locations where space was at a premium.

[2][6] The main lies mostly within London Clay with sections within the overlying alluvium and underlying Lambeth Group and Thanet Sand.

The predominance of the London Clay lengths is by design, as being easily excavated, largely impermeable and somewhat self-supporting for short periods it is a near-ideal tunnelling material.

An indication of this dynamic variation in demand is that the minimum hydraulic level moves between the Battersea and Park Lane pump-out shafts.

The loop is closed to provide the redundancy that allows any segment on the ring to be isolated and drained for maintenance without interrupting the supply to any shaft, not for hydraulic reasons.