Question
Download Solution PDFAs per IS 1742-1983, normally a sewer shall be designed for discharging _______ times the dry-weather flow flowing half-full with a minimum self-cleansing velocity of _______.
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFConcept:
IS 1742-1983: Code of practice for building drainage
Normally, the sewer shall be designed for discharging three times the dry-weather flow flowing half-full with a minimum self-cleansing velocity of 0.75 m/s. The approximate gradients which give this velocity for the sizes of pipes likely to be used in building drainage and the corresponding discharges when flowing half-full are as follows:
|
Diameter (mm) |
Gradients |
Discharge (m3/min) |
| 100 | 1 in 57 | 0.18 |
| 150 | 1 in 100 | 0.42 |
| 200 | 1 in 145 | 0.73 |
| 230 | 1 in 175 | 0.93 |
| 250 | 1 in 195 | 1.10 |
| 300 | 1 in 250 | 1.70 |
Important Points 1. In cases, where it is practically not possible to conform to the ruling gradients, a flatter gradient may be used but the minimum velocity in such cases shall on no account be less than 0.61 m/s.
2. It is undesirable to employ gradients giving a velocity of flow greater than 2.4 m/s. Where it is unavoidable, cast-iron pipes shall be used.
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