Q. Should we prepare a house drainage plan?
Yes. It is always better to prepare house drainage plan. In some cities, it is statutory to submit such plans. We should plan in advance about the position of baths, water closets, urinals, wash basins and other units along with the position of traps, manholes, soak pits/septic tanks, public sewer, as applicable.
Q. What is a septic tank? How does it work?
A septic tank is used to treat sewage from isolated group of country houses, where a piped sewage system (i.e., a public sewer) is not available. It is a horizontal continuous flow sedimentation tank in which sewage moves very slowly. Septic tank serves two purposes: deposition of settling solids in sewage by sedimentation, and partial or complete digestion of the sludge prior to its disposal. A septic tank produces septic action by anaerobic bacteria, wherein proteins, carbohydrates, cellulose and fatty matter present in sewage are broken to simpler compounds. The nitrogen is converted to ammonia, while the colloidal matter is flocculated, then liquefied and finally digested. The effluent from the septic tank is discharged either in to the soak pit or below ground level through drains, so that the effluent gets absorbed in the soil. A baffle wall with openings is constructed at some distance away from the inlet. The sludge, which is deposited in the bottom is cleaned periodically, say once in 6 to 12 months. A vent pipe is provided for the escape of gases.
Q. What is function of a soak pit? What is a sludge soak pit?
A soak pit is a covered pit dug in the ground, in which effluent from the septic tank is discharged. It is generally dug in the pervious soil which can absorb the effluent.
A sludge soak pit is the one in which the sewage effluent from the house drain is directly discharged. The water in the accumulated sewage is soaked by adjoining pervious soil while the sludge is digested in the pit. Such soak pits are very common where subsoil is very pervious. Usually, the pit is lined with masonry with open joints. The top is covered with rigid slab. The diameter of such tank varies from 2 m to 3 m, while depth varies from 2.5m to 4 m. each individual house has one such soak pit which has a life of about 20 years for a family of 6 persons. When the soak pit gets filled up, the top cover is removed and the tank is emptied.
Q. What should be floor level of bath room/kitchen?
The level of bath room/kitchen floor should be 12-20 mm below surrounding floor. The slope of flooring should be towards nahni trap or floor trap.
Q. What precaution should be taken in GI (galvanized iron) concealed pipe line?
It should be pressure tested.
Q. What class of GI pipe is generally used for residential construction?
Class 'B' (medium grade) pipe.
Q. How to fix glazed tiles on walls?
It should be fixed on rough plastered surface with cement mortar 1:1. Neat cement for fixing tiles should not be used.
Q. Can drainage from kitchen/toilet be directly connected to manhole?
No. first, it should be connected to gully trap and then to the manhole.