Drainage - Introduction - Page 1 2 3 
Introduction to Drainage
Drainage schemes for buildings are necessary
to remove waste water, foul water
and surface water.
Waste water and foul water
join together and are disposed in a septic tank in rural areas or to a foul water sewer in urban
areas.
The foul water sewer discharges the sewerage
to a treatment plant where it is settled, filtered and chemically treated.
Surface water can be discharged into a soakaway, to a river or lake
in rural areas or to the surface water (or Storm Water) drain in urban
areas. The storm water drain discharges water safely to a river or lake.
A separate system of drainage is used where foul water
and surface
water are separated at source and piped individually to a surface
water drain or foul water drain.
The diagram below shows a typical arrangement
for a small rural dwelling.
Outlet from septic tank to soakaway – perforated drain
into percolating sub-soil
The diagram below shows a typical arrangement
for a small urban dwelling.
Drainage inside Dwellings
The system of drainage inside
dwellings is installed to that access can be obtained for possible cleaning.
This access is usually at
basin and sink water seal traps and at access bends, branches where used.
The drawing below shows inside
drainage in the single storey dwelling shown above.
