SYSTEM OF DRAINAGE AND VOLUME OF SEWAGE FOR DESIGN REQUIRED FOR THE SELF CLEANSING VELOCITIES.

Inspection chamber is a sort of small man hole or chamber built in any house drainage system which takes wastes from the gully traps and disposes off to manhole, this is for inspection or cleaning. It is provided at every  change of direction or gradient and at the point where the vertical soil pipe joins the house drain. Minimum size of the inspection chamber can be kept 75×60 CM, the longer dimension is in the direction of the main drain line and walls of the inspection chamber can be twenty CM thick. (2) FLUSHING OF DRAINS AND SEWERS:-Where it is not possible to obtain self cleaning velocities due to flatness of the gradient especially at the top ends of branch sewers, which receives very little flow, it is essential that some form of flushing device be incorporated in the system made for the arrangement. As such it is necessary to maintain flushing done at least once in a day(3) SUB SOIL DRAINAGE:-- As far as sub soil drainage is concerned the depth and frequency of the drains may produce satisfactory results and depending upon the character of the soil, the more porous the soil the deeper the drains and deep drains are placed further apart . A depth of 0.61 to 1.22 mt is generally suitable for clay soils and 1.22 mt for the sandy soils. Clay is a soil which is very retentive of moisture and one cubic metre of most dry clay will absorb about160 litres of water. (4) SEWAGE TREATMENT:-- The types of sewage treatment are divided under two heads Primary and the Secondary. Primary treatment comprises of process which include grit settling, plain settling and precipitation of colloidal particles by the addition of chemicals. Secondary treatment includes dilution of sewage by water, land irrigation, trickling filters and activated sludge process. Accordingly the system is designed for the size of sewer and further treatment, adjusted according to the designed velocity, which is generally considered to flow only one -quarter full for calculation of the velocity. It is false economy to save a little by providing a smaller diameter at the expense of possibly having to duplicate it at some future date . Sewers are normally designed as running 2/3 full and leaving top 1/3 for gases . Manhole or inspection chamber are openings through the street surface to the sewers to provide access for inspection and cleaning and provision is essentially made for the all junctions, change of direction or alignment, change of gradient and size of sewer lines connected for the use and minimum internal size of dimension of the chambers having not more than two branch channels on either side should be 90×80 CM for house drainage constructed within the compounds of the building or near about depths of one metre , and in the case of main drainage works it should be kept 1.2×0.90.CM for depths between One metre to 2.5 Mt.