MAINTENANCE OF

SEWRAGE

SYSTEM

MAINTENANCE OF SEWRAGE SYSTEM

The faults in sewer system occurs due to defective system &misuse.

The main problems in sanitary system are as follows:1. leakage of C.I pipes2. overflowing Cisterns3. blocked Waste Pipes4. blocked drains & drainage5. damaged or cracked China Ware.

MAINTENANCE OF SEWRAGE SYSTEM

LEAKAGE OF C.I PIPES:The dampness near C.I fitting normally

occurs on roof due to leakage through C.I fitting.

It is also normally below the water closet

or the floor trap.

The defects occurs due to seepage of water

through the gap between the floor & the

‘P’ trap at the time of original construction.

MAINTENANCE:This leakage can be repaired & plugged by applying a suitable sealant in the gap.The joints are filled with lead to close the gap in collar. Collar can be utilized in forming lead joint on both sides of collar.

DEFECTIVE INSTALLATION Of TRAPS:The maintenance problems of trap arise due to defective

design, inappropriate seal, & defective installations.

DESIGN DEFECT:

may be caused due to loose cover or improper

type of trap.

The proper trap has ‘U’ shaped pipe.

INAPPROPRIATE SEAL:

Water seal should be 38mm in two

pipe system 40mm in single

stack system.

Inadequate water seal create

leakage problems.

DEFECTIVE INSTALLATION:

Defective installation of trap is the main cause of leakage.The defective floor installations can be summarized as:Installation where trap is seated too deep from the floor level,Installation where one or more pipe enters into floor trap,Installation where trap is over flooded.Water tight lead joint shall be provided for avoiding leakage.

OVERFLOWING CISTERNS:

Overflow from the cistern occurs due to a damaged ball cock or due to blockage of the ball valve itself. The ball may develop a crack or leak, which results in filling of the ball with water & thus resulting in ill functioning.

MAINTANANCE:

Leakage can be repaired by the replacement of the ball or the puncture of the ball be sealed after removing the leak water.In case the ball is okay & the fault is in the ball cock then the ball cock is adjusted by bending the rod connected to the valve.Fault can be due to the presence of some grit in the valve, the grit can be removed.

BLOCKED WASTE PIPES:

Blocked waste pipe results in the slow emptying of the fitting to which the waste pipe is connected.

MAINTENANCE:Normally cleaning eyes / plugs are provided in the pipe for cleaning & the same should be opened to remove foreign matter.To decrease the chances of the occurrence of this defect, a strainer should be fixed at the entry point of waste pipe. Flow should be checked in the waste pipe at regular intervals Augers are used for cleaning the waste pipes.

CLOGGED DRAINS & LEAKAGE:Drains may get clogged by large size objects dropped in to them by accumulation of grease, dirt or other matter.

MAINTENANCE:If the obstruction is in the trap, the trap cover can be removed & cleared. If the obstruction is elsewhere in the pipe, cleaning can be done by using extendable rods attached with flushing rubber cups in front. This rod should be moved to & fro in the clogged drains & flushed with water. If the clogging is more hard & difficult, use augers with steel cable. (snake auger). These augers may be run into drain partly to break the obstruction & to hook on to pull out the obstructing objects.Sand & dirt sometimes clog the floor traps & drain. Remove the strainer & take out much of the sediment around the floor trap manually & flush the drain with clear water. If more pressure is needed, use garden hose to clean the clogging.

DAMAGED OR CRACKED CHINA WARE:

Damaged chinaware fittings give a very shabby look in addition to the leakage problem. Chinaware fittings can only be replaced if these are cracked. Washbasins are mostly fixed on iron clamps embedded in wall up to very small depth. A slight displacement can break them. The support angles should invariably be embedded adequately (200-250mm) in the wall so as to make stable. Whenever supporting fixtures are loose, these should be immediately repaired & reset.

DEFECTIVE DOWN TAKE DRAIN PIPES:Down take pipes should be non-perforated and non-leaking.

Metal pipes are favoured as these are non-perforated and

non-leaking, but these pipes

Remedial measures will consist of painting of the inside of gutter and down pipes with bitumen paint.

In case of plastic pipe bowing during hot

season is a major problem.

If joints starts leaking, these need to be

repaired by using appropriate leak proof

sealing adhesive.

SEWERThe under ground drains or conduits through which the sewage is conveyed or carried are called sewers.

Sewage always is carried in closed drains or pipes so that the foul gases and odour may not pollute the atmosphere.

SHAPE OF SEWERSRectangular

Circular made of brick or circular pipes

Semi elliptical

Horse shoe type

Basket handle type

Egg shaped or oval shape section.

Though every shape has its own advantage, and disadvantages, but an egg shaped sections have been found more popular in practice.

CHARACTERISTICS OF SEWERS

As sewage from industries having acids, alkalis and other chemicals also flow through sewers, hence the materials of sewers should possess the following characteristics

Resistance to corrosion and abrasion- the sewer material should be resistant to chemical reactions and abrasion.

Durability- the material of sewers should be durable, so that no frequent replacement of sewer is required.

Imperviousness- the material of sewers should be sufficiently impervious.

Strength- as generally sewers are laid underground, hence they are likely to be subjected to heavy loads. Hence, the material should be strong enough to withstand these loads.

VENTILATION OF SEWERS

Sewer ventilation is essential due to the following reasons-

•Sewage flowing in the sewers contain organic and inorganic matter which on purification or decomposition produces gases like carbon monoxide, carbon dioxide, methane, nitrogen and ammonia etc.

These gases like methane are very foul explosive and may cause fatal accidents to the maintenance gang.

If the sewer is not properly ventilated the man hole cover may be blown off.These gases being light move upwards and cause air pollution when they escape into the atmosphere.

They also interfere with the natural flow of sewer.

Hence sewer ventilators are provided along the sewer lines at an interval of 80 to 150 m or so.

Ventilator shaft may be of cast iron, steel or R.C.C. pipes of internal diameter ranging from 15cm to 25cm.

MAINTENANCE OF SEWERS

•For efficient and proper working of sewer lines, their proper maintenance is essential.

•Maintenance of sewers mainly consists of removal of stoppages, cleaning of sewers and other sewer appurtenances and repair work.

•Maintenance of these sewers is costly which are laid on flat slopes as they are more prone to heavily clogging and the self cleansing velocity is not developed.

•Sewers which are laid to be clogged by the entrance of tree roots through faulty joints are costly to maintain.

•Cleaning of clogged sewers due to silt, grease and oily materials is one of the major problem of maintenance of sewer line and is costly.

•The clogging mainly occurs in small sized sewers, where a man cannot enter into them to clean.

•The clogging may be due to the deposition of sand, silt, grit, and waste building materials and ashes etc.

•It may also be caused by the deposition of grease and oily materials contributed by hotels, garages, soap industries etc.

•Odour in sewers is developed due to the decomposition of organic matter present in the sewage.

•For good maintenance of sewer system, its up to date plans showing location of manholes and other appurtenances, direction of flow, house sewers and grades of sewer line etc should be available.

•Before starting actual cleaning and repair work, the inspection of the sewer line and appurtenances must be carried out.

•In some cities inspection and repair works are carried out periodically as per schedule.

•The period of inspection generally followed is as follwos-Sewers on flat grades 3 months

Sewers not likely to be affected by tree roots

3 months

Trouble free sewers 6 to 12 months

Intercepting sewers 1-4 weeks

Flushing tanks 1 month

Storm water overflow During rains only

CAUSES OF DAMAGE TO SEWERSMain causes of damages to sewer are as follows:

•Use of poor quality materials and bad workmanship.

•Settlement of foundation due to low bearing capacity of soil.

•Excessive super imposed loads and faulty design.

•Small soil cover on the crown of the sewer to withstand the shock, impact, vibrations due to moving vehicles.

•Explosion inside the sewer due to improper ventilation of the explosive gases developed inside the sewer.

•Abrasion of sewers due to grit, sand etc. flowing with the sewage and corrosion of sewer pipe due to corrosive gases which eat away the sewer material resulting in its breakage.

•Breakage due to old age etc.

PROBLEM OF SEWER MAINTENANCE

The major problems the maintenance of sewers occur due to clogging which is cause due to the following reasons-

•Deposition of silt, grit or other such material cause stagnation of sewage causing to decomposition of organic matter present in the sewage, producing poisonous gases and unpleasant odour in the sewer.

•It may also be caused by the deposition of grease and oily materials contributed by hotels, garages, soap industries etc. deposit on the side of the sewer, reducing its cross section, which in course of time clog the sewer.

•Penetration of roots through faulty joints or cracked sewer joints chock the sewer.

•Stagnation of sewage in sewers due to improper working of pumping units leads to the settlement of grit and other materials and dumping of soil waste in the man hole clogs the sewer line.