Correct Option: E

TRAPS
A trap is a device which is used to prevent sewer gases from entering the buildings. Common Gases that are produced in a Sewage System
1. Methane
2. Hydrogen Sulfide
3. Nitrogen
4. Carbon Monoxide

Requirements of good trap:
1. It should be capable of being easily cleaned.
2. It should be easily fixed with the drain.
3. It should be of simple construction.
4. It should possess self-cleansing property.
5. The internal and external surfaces should be of smooth finish.
Classification of traps
Depending upon the shapes the traps are classified as:
1. P-Trap
2. Q-Trap
3. S-Trap
Some other kind of traps are:
1. FLOOR-Trap
2. GULLY-Trap
3. INTERCEPTING-Trap
4. GREASE-Trap
5. BOTTLE-Trap
P Trap

This trap is used with Indian water closet. The traps are made from cast iron or UPV sheet. This trap also has water seal and prevents entry of foul gases to the house.
S Trap

This trap is similar to P trap and is used for fixing water closets in toilets.
The only difference between P trap and S trap is that P trap is used for outlet through the wall whereas S trap is used for outlet through the floor. FLOOR TRAP OR NAHINI TRAP
This trap is provided in the floor to collect waste water from washbasin, shower, sink and bathroom etc.
These are available in cast iron or UPVC material and have removable grating (JALI) on the top of the trap.
The minimum depth of water seal should be 50 mm. GULLY TRAP
These traps are constructed outside the building to carry waste water discharge from washbasin, sinks, bathroom etc. and are connected to the nearest building drain/sewer so that foul gases from sewer do not come to the house.
Bottle Trap
This trap is used below washbasin and sinks to prevent entry of foul gases.