The Building Process

The foul water and surface water systems are two distinct systems, that must be kep separate. Quite often the pipe runs will go in the same trenches and are usually installed together. The Building Inspector takes a keen interest in the foul water but, usually, not so much interest in surface water.



Drop manholes for foul water drains - a way of dropping the level over and above that which would be allowed with the normal gradient allowed for foul water pipes. The height is dropped vertically outside the inspection chamber and a rodding point is also introduced via the upper pipe going into the chamber. Dropping the level for surface water is much simpler - just let the 4" pipes follow the required gradient.


4" drain pipes here are positioned internally. It means there are cleaner lines to the external look of the house but requires extra work internally to box them in, skirting board, coving etc. The two pictures below show a surface water drain being encased in concrete under a driveway.