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close this bookResidential and Non-Residential - Drinking water installations and drainage requirements in Nepal (MTC - SKAT, 1988, 188 p.)
close this folderPART 2 - DRAINAGE REQUIREMENTS
View the document1. SCOPE
View the document2. FIELD OF APPLICATION
View the document3. TERMS AND DEFINITIONS
View the document4. PRINCIPLES OF INSTALLATION
View the document5. PRINCIPAL REQUIREMENTS FOR PARTS OF PIPELINE
View the document6. PRINCIPAL REQUIREMENTS FOR DRAINAGE APPLIANCES
View the document7. PRINCIPLES FOR THE PLANNING AND FITTING OF DRAINAGE PIPES
View the document8. SANITARY APPARATUS (Fixture, Appliance)
View the document9. VENTILATION
View the document10. RAIN WATER
View the document11. MATERIALS
View the document12. PRINCIPLES OF CALCULATION
View the document13. DIMENSIONING
View the document14. INSPECTION AND TESTING

12. PRINCIPLES OF CALCULATION

12.100

GENERAL PRINCIPLES


The dimensioning of a drainage system is based on the following factors:

12.110

Sewer Value (SV) - Sewer accumulation per time unit in l/s of the drainage appliance.

12.120

Duration of drainage - Duration of discharge in seconds (s) of the drainage appliance.

12.130

Probable maximum load - Maximum expected discharge of soil and/or waste water per time unit in simultaneous use of sanitary drainage appliances.

12.140

Loading Capacity - For those under section: “Dimensioning” fixed and permissible loadings are based on following preconditions:



- trouble-free drainage of the waste waters



- warranty of ventilation of the drainage systems and of the ventilation system respectively



- water seal (of siphon) may neither break through by vacuum, nor be pushed out of the siphon due to over-pressure


Note: Larger inner diameters than indicated are not to be used.

12.150

Classification of groups for drainage appliances - All places of discharges of soil and/or waste water (from drainage appliances) are classified in four SV-groups, ref. table: “Nominal sewerage values.” (13.300) The smallest SV is 0.5.

12.160

Soil and/or waste discharges over 2.5 l/s - Drainage appliances with an S-Value larger than 2.5 l/s, as well as continuous discharges (pumped soil and/or waste water plants) are to be treated as special arrangements and their effective drainage capacity to be added to the findings of maximum loading under diagram 1.

12.170

Dish washing machine - The S-value of domestic dish washing machines connected to a siphon of a single or double sink is not to be considered.

12.180

Duration of the discharges of drainage devices - When determining the possible maximum-loading and the dimensioning of drainage arrangements, the following are to be differentiated:



a) short term drainage as for closets, washbasins, etc., which are marked for residential buildings.



b) long term drainage, as for example in industries, trades and in laboratories.

12.200

PRINCIPLES OF DIMENSIONING

12.210

Determination of the possible maximum loading - for the determination of the possible maximum loading serves, above 60 SV, the approximation formula is used:
Vs max. =


this takes into consideration the differentiation of connected drainage appliances of a domestic system.


Below 60 SV the maximum loading is not to be calculated, but determined according to the dimensioning tables.

12.220

Filling ratio: The ratio for filling for ground pipelines or collector pipelines will be assumed, as follows:


Sewer, rain and mixed waste water

12.230

Simultaneous Discharges:- When dimensioning leaders (stacks, collector and ground pipelines), the possibility of simultaneous discharge must be considered. Maximum loading is determined by adding connected discharges in l/s of connecting pipes, as of diagram 1.

12.300

DIMENSIONING

12.310

Connector - and branch pipelines - The dimensioning of the connector line results from table: “Nominal Sewerage values” (Fig. 13.300). The following tables serve for the dimensioning of branch and connector pipelines.


Up to 60 SV determination of the expected probable maximum load is not required.

12.320

Diagram 1 - This diagram serves to determine the expected maximal loadings of a soil and waste water system in a domestic building. The graph converts total S-Values into liters per seconds.


For the calculation of the probable maximum loading with connecting values above 60 SV, the following equation is valid:



Vs max.



(Vs max. = Volume flow of all drainage appliances)



Figure


Reading example:

known: 20 flats at 5 SV = 100 SV
wanted: Probable Maximum Load
solution: Vs =

12.330

Leaders - The permissible loading (Vs) of the leader is variable depending of the ventilation system and assessed in the tables: “dimensioning of leaders” (Fig. 13.500)

12.340

Ground pipelines and collector pipes - Relevant for the determination of the inner diameter (i.d.) for ground pipelines and collector pipes is the maximum expected loading, Vs max. in l/s.



- For soil and/or waste water pipelines the i.d. is determined based on the maximum expected loading (Vs max.), under consideration of the total simultaneous amount of the SV before this point, according to diagram 1.



- For rain water the effective loading of rain water, Vr, is decisive for the determination of the i.d.



- Roof surfaces - The horizontal projection is the base for the calculation of roof surfaces (A in m2)


Figure



- For ground pipelines in mixed systems the maximum expected loading, Vm, results from the amount of Vs max. + Vr.



- Vs = Volume flow of several drainage appliances



- Vr = Flow rate per unit time of rain water



- Vm = Flow rate per unit time of mixed soil, waste water and rain water (in ground pipelines only).