Solution:

• In a two-pipe system the WC waste is fed into a large diameter vertical soil pipe, seperate to the other waste water.
  The key features of this system are:
• WC waste is fed into a large bore soil pipe, which leads directly to the sewage network, and often runs down the outside wall of a property
  Remaining waste waters from washbasins, bath and kitchen sink etc are combined via seperate smaller bore branch pipes in a gully just below ground level.
• To prevent back siphoning and to discharge any gases from the drains, the large soil pipe is vented to the outside above the guttering.
• All appliances contain a u-bend trap full of water to prevent drain smells penetrating the house.
• The waste from the gully finally meets the soil water a short distance from the property on its way to the sewers.
• At this meeting point will be an inspection chamber with a manhole cover.