INDEX1. TRAPS -P,Q,S,TRAPS

-FLOOR TRAP-GULLY TRAP

-ENTERCEPTING TRAP2. SEWER CLEENING

OPRATIONS-FLUSHING-DRAGING

-USE OF PILLS

TRAPS

(a) Classification based on shape :

(1) P-trap(2) Q-trap(3) S-trap

(b) Classification based on use:

(1) Floor trap or Nahni trap(2) Gully trap(3) Intercepting trap

1. Floor trap or Nahni trap:

A floor trap, commonly known as a nahni trap is used to collect wash water from floors, kitchens and bathrooms. It forms the starting point of waste water flow.

It is generally made of cast iron.

Are movable C.I. grating is provided on the top of the trap to prevent the entry of coarse solid matter into the drain. The water seal of the trap prevent the entry of foul gases of sewer line into bathrooms of kitchens.

2. Gully trap:

These are special types of traps which disconnect sullage drain (collect from baths, kitchen, etc.) from the main drainage system. A well designed gully trap serve two or three connections from the nahni traps.

A gully trap is usually made of stoneware and a C.I. grating is provided at its top. A gully trap is fitted inside a masonry chamber and a water seal of 60 to 70 mm is provided.

The gully traps forms the starting point of horizontal flow of sewage it is usually situated near the external face of wall and it is kept slightly higher or even in line with pavement or ground

level. The gully traps leads sewage to a sewer or to an inspection chamber or to a manhole.

3. Intercepting traps.

The intercepting trap is also known as disconnecting trap or interceptor. It is provided at the junction of house drain with the public sewer or septic tank. It is also provided in the last manhole of the house drainage system.

The domestic sewage is carried by the pipe line and allowed to fall in the semi-circular open channel within the manhole as shown in fig. then the sewage flows to the main sewer through the intercepting trap. The primary object of providing intercepting trap is to prevent foul gases in the public sewer from entering the house drainage system. It also has an inspection arm which is kept closed by plug. The plug is opened for cleaning or inspection of the pipe lines. The plug and is also called ‘cleaning eye’.

SEWER CLEANING OPERATIONS:

(a) Flushing(b) Dragging(c) Use of pills

1. Flushing

In case of large sewers, cleaning is done manually. The man enters the sewers through manhole and scraps the sides of sewer by brushes. The scraped material is removed through manholes.

In case of small sewers, cleaning is done by flushing. For this purpose, automatic flushing tanks are sometime installed on the sewer line. A fire house may be also interested in the sewer

and the water under pressure may be discharged through the hose clean the sewer.

Sewer flushing in use this method.

-By using self flushing tanks

-By flushing manholes

-By use of fire hose

-Connecting with water mains

-By temporary stoppage and release ofsewage in sewer line

2. Dragging

-By thrusting rods

-Flexible wooden rods fitted with special cleaning tools

-By using steel tape or band with special tools

3. Use of pills

This is interesting method of cleaning the sewer. In this method, small pills or balls made of wood or rubber or hollow metal covered with canvas are put in the manhole above the obstruction. The pill floats in the sewage and when it comes near the obstruction, it is caught there and the sewage start collecting behind it. When sufficient head is developed, the accumulated sewage removes the obstruction and the pill is caught in the next manhole.

Then a pill of slightly larger diameter than the previous one is taken and the process is repeated until a pill having diameter about 25mm less than that of sewer passes easily from one manhole to other.

REFERENCE

1. WWW.GOOGLE.COM

2. WS&SE TEXT BOOK

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