A sewer is an under ground conduit or drain through which sewage is conveyed to the point of discharge or disposal. Therefore it is obvious that joints will be there in it. Joints in sewers can be of the following types –
- Bell and spigot joint
- Collar joints
- Simplex joints
- Flexible or bituminous joints
- Mechanical joints
- Open joints
1. Bell and spigot joint
Such joints are quite common in plain or reinforced concrete pipes of sewers. Each pipe has a spigot end and a bell or socket end. Cement mortar of proportion 1:1 or 1:2 inserted between the space of the bell end and spigot end. Gasket or jute packing may placed in the inner side, to maintain the alignment of the sewer. The mortar caulked joint thus finished at about 45 degree on the outer face.
2. Collar joints
For such a joints in sewers, the plain ends of the consecutive lengths of pipe are kept near each other. A collar of slightly bigger diameter is place’d around. The annular space between the collar and the ends of the pipe then filled with cement mortar of 1:1 proportion. Such joints thus used for concrete pipes of larger diameters.
3. Simplex joints
Simplex joint, also referred as ring tie coupling, is similar to collar joints. These are used for asbestos cement pipes. Thus the joint consists of a pipe sleeve or coupling of asbestos cement. Also it has two rubber rings which then compressed between the exterior of the pipes and interior of the sleeve. Such a joint is quite flexible.
4. Flexible or bituminous joints
Flexible joint is also termed as bituminous joint. The collar joint, using cement mortar is relatively rigid. Such joints crack easily due to even slight movement pipes due to settlement etc. These joints, made flexible by using bitumen instead of cement mortar.
5. Mechanical joints in sewers
Such joints use mechanical devices like flange rings, bolts, screwed ends etc. so that to keep the two ends together. Therefore it, used for metallic sewers made of cast iron, steel etc.
6. Open joints in sewers
If there is no objection to infiltration, open joints can however be adopted in sewers. The bell and spigot ends simply placed together, without inserting filling material in the annular space. Gasket may however be inserted; to maintain alignment. The joint is merely covered with tar paper,this is because to prevent entry of subsoil into the sewer.