DIMENSIONING WATER SUPPLY SYSTEM IN BUILDING

Size: px

Start display at page:

Download "DIMENSIONING WATER SUPPLY SYSTEM IN BUILDING"

Lauren Lynch
6 years ago
Views:

1 1 Mamk Department of Energy and Environmental Technology, ET Double Degree Programme in Building Services T6615KA JukkaRäisä Water and sewage services in buildings DIMENSIONING WATER SUPPLY SYSTEM IN BUILDING 1. General Criteria for dimensioning of pipe network - Every tap gives adequate and steady water flow - No hydraulic hammer effects - Low noise, flow velocities are suitable If available pressure in the network (after main water meter) is greater than 500kPa, pressure must be dropped by installing of decompression valve which is then set to the pressure level required by dimensioning. If it is necessary, decompression valve in each flat is used. If pressure is kPa, could decompression valve be used depending on floor height and pressure losses of faucet in standard flow. If pressure level is too low (for instance high buildings), booster pumping is used. By the dimensioning used explications is fig 1. p0 Pressure level at connection point of distribution line and service line. (Water main pressure)

2 2 Local Waterworks announces the pressure (P0) in the distribution line. pn Pressure which is used to connection pipe and faucet flows. pn is calculated at the elevation of faucet. Pressure available at the level of the faucet overcomes the resistance of flow in the connection pipe and the faucet. The pressure pn is used in design by calculation. pn is calculated from po or by reducing from this. The pressure drop ( Hk) due to the difference in level between the water outlet and the distribution pipe, and the pressure losses in the service pipe, water meter, water heater and distribution pipes ( p). pn is calculated separately for the cold and warm water pipes. pa Available pressure after the decompression valve Pressure pn shall be calculated from pressure pa in same way, but level difference shall be calculated from level of the decompression valve, and pressure losses in site water pipe and water meter should not be taken into account.

3 3 Line 1 Line 2 connecting pipe main supply water meter service pipe distribution pipe Fig. 1 Definitions of terms used in designing water supply systems n number of storey s with water outlets K 1-4 water fittings 1-4 p pressure losses in pipe section

4 4 2. Dimensioning Dimensioning step by step: (1) Determine standard flow of each faucet (and connection pipe), position 3 dimensioning table 1 (2) Calculate sum of standard flow for each distribution section (Q). (3) Calculate the dimensioning flow (q) for each section of distribution pipe - hot and cold water separately, position 4. Dimensioning flow always define sum of standard flow. (4) Determine dimensions of distribution pipes, position 4, fig. 3 (Choose the tube diameter so, that flow velocity is 2,0m/s). (5) Determine dimensions of connecting pipes, position 5, dimensioning table 4 or 5 (Maximum flow usually 3 m/s). (6) Do the volume flow check which is based on calculations of pressure losses. Every faucet must provide water flow that is 70% - 150% from its standard flow. (0,70 qn q 1,50 qn). (7) The set point of decompression valve is based on calculations of pressure losses. (8) If pressure losses are too high then make larger pipe diameter. Or dropping pressure level shall be reduced by leaving off the decompression valve. Calculations of pressure losses make allowance for the changes in static pressure due to differences in elevation and pressure losses in pipes (service pipe, water meter, water heater, distribution line, connection line, pipes fittings, valves, faucets). Pressure losses are calculated by the dimensioning flow (q). If decompression valve, which is situated usually immediately after the water meter, is used, pressure losses before decompression valve is not necessary to be taken into account, if pressure difference pb-pa is at least 100kPa. The pressure loss in the decompression valve with the dimensioning flow shall be taken into account in design. Water works always do the dimensioning of the property s water meter and the service pipe.

5 5 TABLE 1 Standard flows for design Water outlet Standard flow q N, l/s Cold water Hot water Bath 0,3 0,3 Bidet 0,1 0,1 Sink 0,2 0,2 Sink unit (bucket sink) 0,2 0,2 Dishwasher, domestic 0,2 (0,2) Shower 0,2 0,2 Tap 0,2 0,2 Washing machine, domestic 0,2 Washing machine, in laundry room or similar 0,4 0,4 Garden valve In single family house DN 15 0,2 In block of flats DN 20 0,4 Wash basin 0,1 0,1 Urinal with flushing valve 0,4 Urinal with flushing tap 0,2 WC 0,1 WC with flushing valve 1,5 1) Grouped outlets Shower group n*0,14 1)2) n*0,14 1)2) Flushing valves in series for urinals 0,3+n*0,1 1)2) Flush taps in series for urinals 0,14+n*0,06 1)2) WC flushing valves coupled in series 1,3+n*0,2 1)2) Group of wash basins or trough basin 0,07+n*0,03 1)2) 0,07+n*0,03 1)2) Fire hydrant See Clause 2.9. Other industrial use To be calculated separately Notes to table 1: 1) Simultaneous demand is to be taken into account in accordance with Table 2. 2) n = number of fittings in the group. If the fitting has alternative outlets, the maximum flow is to be used in design. A device which supplies water for a consumer unit such as a washing machine through an easily demountable connection is also considered to be an outlet.

6 6 2.1 Dimensioning flow in distribution pipes The dimensioning flow of distribution pipe define is by sum of standard flows by formula 1. Dimensioning of distribution pipe is used fig.2 and table 2 dimensioning flows. In dimensioning of distribution pipe, a total standard flow of (Q) 0,8 dm 3 /s for cold water and 0,8 dm 3 /s for warm water may be appointed for each flat, single family house and similar even though the aggregate flow according to the table is more than 0,8 dm 3 /s. A separate pipe for kitchen or bathroom in a dwelling may be designed without consideration of the standard flow for a washing machine or dishwasher which is connected there, provided that the dimensioning flow of the pipe in question 0,2 dm 3 /s. In designing distribution pipes common to a number of dwellings, consideration shall be given to the flows which occur. The dimensioning flow in the distribution pipe is obtained from the formula: 1 q = dimensioning flow, dm 3 /s, also known as probable flow and design flow qn1 qm Θ Q A maximum standard flow in pipe being dimension (dm 3 /s) mean flow through valve in question, (dm 3 /s) probability that qm is used during peak consumption periods aggregated standard flows through the connected water outlets, (dm 3 /s) correction factor which takes account of the number of times that the dimension flow q is exceeded

7 Uncertainty 1 0,01 0,001 0,0001 Factor A 2,3 3,1 3,7 In calculating the dimensioning flow of

buildings, the following values are to be used: qn1 = 0,2 dm 3 /s (without bath), 0,3 dm 3 /s (with

is greater. Values of the dimensioning flow (q) is calculated with these values is set out in Table 2.

7 7 Uncertainty 1 0,01 0,001 0,0001 Factor A 2,3 3,1 3,7 In calculating the dimensioning flow of distribution pipes in residential and office buildings, schools, hotels, hospitals and other similar buildings, the following values are to be used: qn1 = 0,2 dm 3 /s (without bath), 0,3 dm 3 /s (with bath) qm = 0,2 dm 3 /s Θ = 0,015 A = 3,1,, (2) Maximum q N1 in use is 0,3 dm 3 /s, even standard flow is greater. Values of the dimensioning flow (q) is calculated with these values is set out in Table 2. Aggregate standard flow Q, dm 3 /s Fig. 2, Dependence of the sum of standard flow and inner diameter of distribution pipe

8 1 The probability of the required flow (standard flow) not being reached shall be taken into consideration. 8

9 9 2.2 Pressures and pressure losses Units of the pressures: Water column pressure mwp (Fin: mvp) International System of Units (SI) N/m 2 = Pa (Pascal) It is an appropriate unit to used kpa for dimensioning of water supply system. 1,0 mwp = 10 kpa 2.3 Available static pressure p st Difference of static pressure (= static pressure loss) h st +H 2 h st H 2 +H 1 H 1 0-level Fig. 4.1 Difference of static pressure (= static pressure loss) h st Difference of static pressure is calculated by formula: (3) hst H2 H1 difference of static pressure, m mwp kpa point of sight level 2, m point of sight level 1, m

10 10 Dimensioning of water supply systems are interested available static pressure p st. Water main pressure (+H 2 ) Point of sight level (+H 1 ) p st H 2 H 1 Fig. 4.2 Available static pressure p st Available static pressure is calculated by formula: (4) pst p0 H1 available static pressure, m mwp kpa water main pressure, m point of sight level, m 2.4 Pressure losses due to flow rate 5 Fig. 4.3 Local pressure loss of pipe section The local pressure loss of the pipe section is calculated following formula. (5) 0,5 (6) p local pressure loss, kpa

11 11 R l Z pd friction loss per one meter of pipe, kpa/m pipe length, m the pipe part s single (local) resistance pressure loss, kpa sum of pipe part's coefficients depended on the nature of local resistance dynamic pressure, kpa density of the fluid, kg/m 3 v rate of flow, m/s Pressure losses in distribution pipes: Σ Σ (7) (8) p sum of the local pressure losses, kpa Available pressure p n Σ (9) pn pst p available pressure for the connection pipe and faucet. (Static pressure is calculated to the elevation of faucet.), kpa available static pressure of the faucet height, kpa sum of local pressure losses from the connection point of municipal water work and service pipe to the beginning of the connection pipe which is gone at the issue faucet, kpa Faucet, P v Connection pipe, P k p st P n H p Distribution line, p Fig Available pressure p n

12 Pressure losses in the connection pipe: Pressure losses of the connection pipe are calculated the same way as pressure losses of distribution pipe section. (10) 0,5 (11) p R l Z pd local pressure loss, kpa friction loss per one meter of pipe, kpa/m length of connection pipe, m the pipe part s single (local) resistance pressure loss, kpa sum of pipe part's coefficients depended on the nature of local resistance dynamic pressure, kpa density of the fluid, kg/m 3 v rate of flow, m/s Distribution pipe FAUCET p vn p TBE Manifold Connection pipe p KN Fig Pressure losses in connection pipe When you have dimensioned flexible plastic pipe as PEX-pipe, you may be used following formula: (12)

13 13 TABLE 4 Connection pipes for outer diameter of copper pipes. The maximum length standard value is given for hydraulic hammer s decreasing. Standard flow, qn Pipe size* Velocity Friction loss per one Maximum length of dm 3 /s d u x e m / s meter of pipe, kpa/m connection pipe, m 0,1 10 x0,8 1,8 9, x 1,0 1,3 3, x 1,0 0,8 1 >10 0,2 12 x 1,0 2,6 14, x 1,0 1,5 3,8 5 0,3 15 x 1,0 2,3 8, x 1,0 1,5 2,8 5 0,4 18 x 1,0 2 4, x 1,0 1,3 1,5 10 * Pipe size du x e = outer diameter of pipe and thickness of pipe wall, mm TABLE 5 Connection pipes for inner diameter of plastic pipes. The maximum length standard value is given for hydraulic hammer s decreasing. Standard flow, qn Inner diameter Velocity Friction loss per one Maximum length of meter of pipe, dm 3 /s of pipe, mm m / s kpa/m connection pipe, m 0,1 10 1,3 2, ) 0,9 1,1 15 0,2 10 2,6 8, ) 1,8 3, ,5 2,5 20 0,3 10 3,8 18, ) 2,7 7, ,3 5,1 15 0, , ) 2 3, ) 1,3 1, ,3 1,1 20 1) Multilayer pipe

14 14 The pressure loss in the water fittings and in its connection pipe with standard flow can be calculated by following formula: (13) p nn p kn p v the total pressure loss in the water fittings and in the connection pipe with standard flow, kpa the pressure loss in the connection pipe with standard flow, kpa the pressure loss in the water fittings with standard flow, kpa The flow from the water fittings can be calculated by following formula: (14) q flow from the water fitting, dm 3 /s p n p nn q N the water fittings and connection pipe s pressure on the water fittings level, kpa. the total pressure loss in the water fittings and in the connection pipe with standard flow, kpa standard flow in the water fitting, dm 3 /s. The friction losses in the copper and plastic pipes are calculated according to fig. 8 and fig. 10. The coefficient of the local pressure loss in the pipe equipment and in the pipe system s fittings due to local resistance can be taken from table 6. Or it can be given by manufacturer and from the hand books. The value of the pressure loss pv in the water fittings with standard flow qn can be given by manufacturer, but it must be at least 150 kpa anyway.

15 15 TABLE 6 Local pressure losses due to local resistance: (the coefficient of loss) Pipe fittings r/d or direction of flow Local resistance coefficient Comment Bend r is radius of curvature d is inner diameter Elbow The local resistance Branch Direction coefficient relates to rate of flow after the branch. Direction Direction

16 16

17 17

18 18 Correction coefficient for the different temperatures: Roughness: 0,0005 Fig. Pressure loss diagram of Uponor PEX and Uponor CombiPEX PN 10

19 The requisite pressure pa If there is needed to use decompression valve, the requisite pressure pa is calculated following formula: (15) NOTE! Remember right sign of 100 (16) Fig Requisite pressure p a

SIZING OF WATER PIPING SYSTEM

SIZING OF WATER PIPING SYSTEM (This appendix is informative and is not part of the code.) SECTION AP101 GENERAL AP101.1 Scope. AP101.1.1 This appendix outlines two procedures for sizing a water piping