| The underground drain system of a house takes the | | | | boundary of the properly. |
| wastes from soil pipes and gullies to the main public | | | | In most cases these drains do not carry rain-water - |
| sewer (if the house is on mains drainage) or to a | | | | sewers and sewage plants would have to be made |
| septic tank or cesspool (if mains drainage is not | | | | much bigger if they did. Instead the rain-water either |
| available). | | | | from the gutters and rain¬water pipes or from the |
| The layout of underground drains is rather less | | | | surface-water drains in a drive, say - is carried through |
| standardised than that of above-ground soil and waste | | | | a separate set of drains either to a public |
| pipes, and because it is hidden it is a little more difficult | | | | surface-water drain, or to a soakaway in the grounds |
| to trace. | | | | of the house. A house may have a soakaway even if |
| Here there are just two con¬nections to the drain | | | | the foul drains are connected to a main sewer. |
| one at the foot of the soil pipe and one from the gully. | | | | A different drain layout is often used when there is a |
| There is no trap at the base of a single-stack waste | | | | group of houses together. There is only one |
| pipe (or at the base of the WC soil pipe in a two-pipe | | | | connection to the sewer, and from this runs a |
| system); the gully has a trap incorporated in it and so | | | | com¬munal drain through the back gardens of all the |
| do pipes carrying waste from fittings other than the | | | | properties. The individual house drains are connected |
| WC in a two-pipe system. To gain access to the | | | | to this communal drain. This clearly saves money and |
| drains in order to clear any blockages - there are | | | | effort when several houses are being built at the |
| inspection chambers. These are sited near the | | | | same time but because the responsibility for the drain |
| connection with the soil-stack, where the drain turns a | | | | is shared, there can be more headaches for the |
| right-angle at the side of the property, and at the | | | | householders when something goes wrong. |