TRAPS• Traps are defined as fittings at the end of soil pipes of waste pipes to prevent foul gases coming out of the soil pipe/ waste pipe
TRAPSTraps are an integral part of a modern sanitary system, beingdesigned to retain a small quantity of the waste water fromthe discharge of fitting to which they are attached as a barrierto prevent foul air entering the building as shown in FigureTraps should be self-cleaning, that is to say , they should bedesigned so that their walls are scoured by the dischargingwater. One of the advantages of modern traps constructed ofplastic materials is the ease with which they may bedismantled for cleaning.
Traps And Pipes and other components of house Drainage System• Following are the main components of House drainage system.• Traps: Good Traps should have following Qualities:• Should provide enough water seal ( around 50 mm) with large surface area.• Interiors surface should be smooth so that the flow is not obstructed which enables self cleansing.• An assess door should be provided for cleaning the trap.• It should be made of non- adsorbent material.
Classification of Traps• Depending upon the shapes the traps are classified as:• P-Trap• Q-Trap• S-Trap• Above three types of traps are shown in the following figures.• The depth of a Trap Seal would depend upon the usage of a pipe. The trap seal varies from 25 to 75 mm deep.
Advantage of Intercepting Traps• Foul Gases of larger municipal sewers are prevented from entering house drainage system.• Harmful pathogens are not entered in house drains.• Well designed and contructed interceptors can quickly remove foul matter of house drain to muncipal sewers.
Loss of Trap Seals If a trap seal loss, smells from the sanitary appliances would enter the building. Therefore the water seal in the trap must be maintained under all circumstances.
1) EvaporationWhen trap is not being used, the rate of waterevaporation depends upon the relative humidity of theair in the room. The rate is approximately 2.55 mm perweek, so a 25 mm seal would last for 10 week. See Figure3.6. Figure 3.6 : Evaporation occur when trap not being used
2) Capillary attractionIs another rare occurrence which happens in ‘S’ trap when a piece of porous material being caught over the bend of a trap absorbs water and deposits it down the waste discharge pipe. See Figure 3.7. Figure 3.7 : Capillary attraction
3) Momentum 4) LeakageThis is caused by a sudden It is caused by a fault in thedischarge of water from a trap or plumbing installationbucket. Due to velocity water and water on the floor wouldis discharged and it shoots be apparent.around the trap bend andgoes down the waste pipe,leaving no seal.5) Wavering outThis is caused by the effect of thewind which passes over the top ofthe ventilation pipe and thus causespressure fluctuations. See Figure3.8. Figure 3.8 : Wavering out
6) Compression or back pressureThis occurs in high rise buildings. When water is discharged down tothe main discharge stack, air is compressed at the base of the stack. Awaste pipe connected to the stack in the pressure zone may have theseal of the trap lost by the compressed air forcing out the water.Detergent foam increases the risk of compression. See Figure 3.9 .
7) Induced siphonageThis is caused by discharge of water from another sanitaryappliance connected to the same discharge pipe. In either avertical or horizontal main waste pipe, as water flows down thepipe and passes the branch pipe connected to it, it draws airfrom it, thus creating a partial vacuum and subsequentlysiphonage of the trap takes place. See Figure 3.10.
8) Self siphonageThis is caused byappliances such as washbasins and other smallappliances, due to theircurved shape, and iscaused by a moving plugof water in the wastepipe. A partial vacuum iscreated at the outlet ofthe trap, thus causingsiphonage action takesplace. See Figure 3.11.