Where the water goes after use

Most houses built before the mid-1960s have what is known as a two pipe drainage system for waste-water disposal. A soil and vent pipe fastened upright to an outside wall carries waste from upper floor lavatories to an underground drain, the pipe is covered with a wire guard, reaches just above the eaves and allows the escape of gases. Ground floor lavatories have an outlet direct into the underground drain. SW11 Plumbers work on waste pipework.


A second, narrower, outside pipe, known as a waste pipe, carries used water from baths, sinks and showers to discharge over a gridded drain gully, often the same drain into which the kitchen sink discharges. Modern houses have a single stack drainage system whereby waste from all sinks the lavatories is carried underground by a single pipe known as a stack. SW11 Plumbers can fit new stack pipework on a property. This stack is often built into the wall and its top protrudes above the roof. Whatever the drainage system, every bath, basin or sink in the house is fitted with a trap, or a bend in the outlet pipe, near the plughole. This holds sufficient water causing a barrier that will stop gases from the drain entering the housing causing a smell. The trap has some means of access for clearing blockages. All lavatory pans have traps, with no access.

Below ground, the household waste pipes are channeled through an inspection chamber near the house to form the main drain, which runs into the water company’s sewer.


Single stack drainage system:
Waste from sinks, basins and lavatories is all carry to underground drains down one pipe.

Two pipe drainage system:
Lavatory waste is carried down one pipe, and waste from bath and basin down a separate pipe.