External Drainage systems Flashcards
Drainage
System of pipes used to convey (transport) the discharge from roofs, paved areas and sanitary fitments (aparells sanitaris) to a point of discharge or treatment
Where should the building owner discharge the storm and foul water?
Into the government’s provisions, if the government foul and storm water pipes are available in the vicinity of the building.
What happens if there is no government drainage provision around (ex: rural areas)?
The building owner should provide sewage treatment
Where is the drainage system installed?
Below the ground level, horizontally or with a gentle gradient
What is a separate system?
Foul water from sanitary appliances is conveyed by a foul water drain into a foul water sewer. Rainwater from roofs and paved areas is conveyed by a rainwater drain to a storm water drain.
Foul water system
Storm water system
What is a combined system?
Foul water from sanitary appliances and rainwater from roofs and paved areas are conveyed by a single drain to a combined system.
One pipework system serves the two discharges.
What is a partial separate system?
Most of the rainwater is conveyed by a rainwater drainage system but some of the rainwater is connected to foul water pipe.
Why use a partial separate system?
In rainy days , the rainwater will flush and clean the foul water pipe. Since the majority of the rainwater goes to the rainwater system, the rainwater going into the foul water system does not overload the system.
Differences between separate and combined systems?
Separate increases the cost of building drainage and the risk of wrong connection is higher. The foul water pipe can only be cleaned by its one water flow(self cleaning) while for combined systems cleans the water pipe by rainwater.
However, the sewage disposal treatment plant is larger for combined systems, but less maintenance costs.
What system is adopted in hong kong?
Separate drainage system
