- A trap is bent or depressed sanitary fitting which always remains full of water.
- Water which remains in it is water seal, which is measured as the vertical distance between crown and dip of a traps.
- The depth of water seal in practice varies from 25 mm to 75 mm.
- The main function of a it in a drainage system is to prevent the passage of foul air or gases through it.
- Also it allows the sewage to flow through it.
- The traps are classified in the following two ways
- According to shape
- According to use.
1.According to shape:
- Traps according to shapes are as follows:
1. P-trap :
- One which has shape of letter P is known as P-traps.
- The legs of it are at right angles to each others.
- One which has shape of letter Q is known as Q-traps.
- The legs of traps meet at an angle other than right angle.
- One which has shape of letter S is known as S-traps.
- The legs of it are parallel.
2.According to Use:
- Traps according to use are as follows:
- Floor trap
- Gully trap
- Intercepting trap
- Floor one is also known as nahni traps.
- One provides a cast-iron cover with grating at top, so as to prevent entry of solid matter.
- However One can remove cover for cleaning of the traps.
- Location: Nahni traps are located in bathroom.
2.Gully traps :
- One usually makes it of stoneware and provide a cast-iron grating at its top.
- One provides water seal of a height of 60 to 70 mm.
- One keeps it at floor or pavement or ground level.
- It leads the sewage either to sewer or to inspection chamber or to manhole.
- A CJ cover is provided at top so that cleaning can be done by lifting the cover.
- The gully one forms the starting point of horizontal flow of sewage.
- One locates it near the external face of wall and keeps it slightly higher than ground level.
- The main idea of providing the intercepting one is to prevent the entry of sewer gases from public sewer line into the house drains.
- This one has water seal of 100 mm.
- It contains an inspection arm for the purpose of cleaning or inspection.
- One keeps the inspection arm closed by a plug or lid.
- A fresh air inlet is also provided in the manhole containing the intercepting traps.
- Location: Intercepting one is provided in the last manhole at the junction of house drain and public sewer line..
Following are the good qualities :
- Firstly, It should be of simple construction.
- It should possess adequate water seal.
- Lastly, One should clean it easily.
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