Examinations on Water Supply Load Calculation Methods of Office Building: Comparison between Conventional Design Methods and the Simulation Methods

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1 Examinations on Water Supply Load Calculation Methods of Office Building: Comparison between Conventional Design Methods and the Simulation Methods G.Z.Wu (1),K.Sakaue(2),K.Kojima(3),K.Fujimura(4),S.Murakawa(5) K.Hayakawa(6) Dept. of Architecture, School of Science and Technology, Meiji University, Japan 3. Mechanical & Electrical Engineering Dept. Architectural Design Division, Lecturer at School of Science and Technology, Meiji University, Japan 4. Mechanical & Electrical Engineering Dept. Architectural Design Division, Kyoritsu Estate CO., LTD, Japan 5. Organization Hiroshima University Graduate School of Engineering Social and Environmental Engineering, Japan 6. Mechanical & Electrical Engineering Dept. Facility Design Division, Toda Corp., Japan Abstract In Japan there are 4 kinds of water load calculation methods based on SHASE-S 26 and 2 kinds based on the Building Equipment Design Criteria of Ministry of Land, Infrastructure, Transport and Tourism to apply to designing of a water supply system in office buildings. However, as water-saving measures of plumbing fixture have seen considerable progress in recent years, these methods were found to produce overestimated values in designing a water supply system. In order to address this problem, a simulation program, MSWC (Murakawa s Simulation for Water Consumption) that enables to dynamically predict water usage has been developed. In this study we collected actual water consumption data from an 8-story office building, processed them through both the conventional calculation methods and the simulation program, and compared the results to evaluate the effectiveness of a water supply system designing method based on MSWC. 529

2 Keywords Water supply demand; calculation method; office building; simulation 1. Introduction Currently in Japan, the methods from Building Equipment Design Criteria of Ministry of Land, Infrastructure, Transport and Tourism (MLIT) 1) and SHASE-S 26 developed by The Society of Heating, Air-Conditioning and Sanitary Engineers of Japan (SHASE) 2) are using to calculate water supply load. The Building Equipment Design Criteria of MLIT defines a method of determining capacity of water storage tanks. Maximum water consumption per day, water consumption per unit time, and maximum momentary water consumption can be calculated by using the method. SHASE-S 26 by SHASE, which stipulates a method of determining the water supply pipe diameter, can calculate maximum momentary water consumption only. However, as there has been rapid progress of water saving measures in sanitary facilities since the 197s and 8s when these criteria were developed, we face a danger of overestimation if we continue to calculate water load based on the basic fixture units used in them. Therefore, we are in need of renewing facilities design criteria based on the performance of the sanitary facilities currently in use. On the other hand, MSWC, a simulation program, which can dynamically estimate water consumption in buildings by using a probability model depends on the estimated consumption of water, has been developed. In this study as a first step of reevaluating water load calculation method, we examined the validity of maximum water consumption per day calculated by the Building Equipment Design Criteria of MLIT based on average water consumption per day as measured by a water meter once every two months in a target building. We also compared the method defined in the Building Equipment Design Criteria of MLIT with daily water consumption estimated from the basic fixture unit applicable to watersaving sanitary fixtures and with values estimated by MSWC. 2. Water Consumption in the Target Building 2.1 Outline of Water Supply System in Building In this study, experimental data were obtained from an 8-story office building (gross floor area of 3,755.1m 2 ) completed in March 211. As is shown in the diagram of the water supply system in Figure 1, the target building is equipped with a rainwater storage tank and storm water filtration system for greening the wall and roof, which are used as a water source of outdoor lawn faucets. A straight-pressure water supply system is installed in the common use space on the 1 st floor and an increase-pressure water supply system is installed to supply water from the 2 nd to 8 th floors. 53

3 Figure 1 Water supply diagram Water supply systems are shown in Table 1, and sanitary fixtures installed are indicated in Table 2. Water supply system Table 1 Water supply systems Straight-pressure water supply system Increase-pressure water supply system (Operation method: Single operation method, Booster pump specifications: 5φ 28L/min.45MPa, Rated power: 3.7 kw Table 2 Sanitary fixtures Fixture 1F 2-8F (Each floor) Roof Outdoor Total WC 1 4 x Urinal - 2 x Wash basin 1 4 x Cleaning sink - 1 x Water faucet in hot water supply room - 1 x Faucet Lawn faucet (1) Data of water consumption (quantity consumption) were taken from water expense sent every two months over the period of April 211 to August 212 (referred to as water meter data below). The data were divided by the number of business days during the period to obtain average water consumption per business day. (2) Cumulative water consumption in each data collection period and average water consumption are shown in Table 3 and Figure 2. Period Water consumption [L] Table 3 Water consumption by period No. of business day [d] Average water consumption per business day [L/d] 4/1~5/18 11, /19~7/19 19, /2~9/17 61, 43 1,419 9/18~11/17 287, 4 7,175 11/18~1/19 429, 41 1,463 1/2~3/19 245, 42 5,833 3/2~5/17 225, 39 5,769 5/18~7/18 241, 43 5,65 531

4 Average water consumption per day [L/d] 25, 2, 15, 1, 5, 4/1~5/18 Average water consumption per day Water consumption 5/19~7/19 7/2~9/17 9/18~11/17 As there were no tenants occupying the building during the period from the completion of the building to September 17, water consumption was at a minimum in that period. The reason for the large consumption in the period September 18 ~ January 19 is that potable water was used for watering the lawn because of the lawn faucets which were intended to use rainwater as a source was not operated normally. As water consumption became stable from January 2, 211 onwards when lawn faucets started to function properly, the average value in that period, 5,736 L was used for comparison. 3. Calculation Method of Design Criteria 5, 4, 3, 2, 1, Based on the Building Equipment Design Criteria of MLIT (referred to as the design criteria below), we compared daily water consumption as calculated from monthly water consumption in the target building and daily water consumption obtained from the calculation method of the design criteria. The design criteria stipulate two load calculation methods (Table 4). The basic unit of load calculation described in the design criteria (referred to as conventional basic fixture unit) and calculation results obtained by using basic fixture unit appropriate for water-saving sanitary fixtures installed in the target building (referred to as proposed basic fixture unit) were compared. Unit water consumption per person per day is designated as Q, unit water consumption per fixture per use as q, daily water consumption as Q d, average water consumption per hour as Q h, and maximum water consumption per hour as Q hm. Since the WCs installed in the target building were the hybrid type with flush volume of 4.8 L combining water supply pressure and small tanks, they were regarded as flush tank type WCs when calculation was made. Calculating procedures in the personnel method and the fixture method are shown in Figure 3 and 4. 11/18~1/19 1/2~3/19 Water meter data collection periods Figure 2 Water consumption per period and average water consumption per day Table 4 Load calculation methods 1) of the Ministry s design criteria Building Calculation method Abbreviated name Equipment Calculation method based on personnel Personnel method Design Criteria of MLIT 1) Calculation method based on sanitary fixture Fixture method 3/2~5/17 5/18~7/18 Water consumption [L] 532

5 q d N q...(1) q h q d t...(2) Q h q h 1 q h 2 q h 3...(3) Q hm K Q h...(4) N: Personnel per user type q h : Average water consumption per person per day by user type q: Water consumption per day by user type Average expected water consumption per hour by user type Q h : Average expected water consumption per hour K: Coefficient of maximum water consumption per hour (normally 2) Figure 3 Calculation flow of water consumption based on personnel q hm q n N...(5) Q hm q hm1 q hm2 q hm3...(6) Q h Q h m K 1...(7) q: Water consumption per use by fixture type (L/use/unit) n: Maximum number of use per hour by fixture type N: Number of fixture by fixture type q hm : Maximum water consumption per hour by fixture type Maximum expected water consumption per hour by fixture type Q hm : Maximum expected water consumption per hour K 1 : Coefficient of maximum water consumption per hour (normally 2) Q h : Average expected water consumption per hour Figure 4 Calculation flow of water consumption based on fixture 3.1 Calculation of Water Consumption by Personnel Method Q of the target building was set to 8 L/(person/day) 1). Daily water consumption was calculated based on the number of hours per day by user type as 8 hours. As shown in Table 5, daily water consumption of 43,6 L/d was obtained. Table 5 Calculation of Water Consumption by Personnel Method Floor Room Effective area [m 2 ] Personnel density No. of people Unit water consumption Q[L/(p*d)] 3.2 Calculation of Water Consumption by Fixture Method Daily water consumption Q d [L/d] No. of hours used [h/d] (1) Calculation of water consumption based on conventional basic fixture unit Average water consumption per hour Q h [L/h] 3~ x x 6 8 6,4 x x 6 Office , Administrative room Total ,6-5,45 Daily water consumption Qd[L/d] 43,6 43,6 Water consumption per use by fixture type and maximum number of use per hour by fixture type are shown in Table

6 Daily water consumption obtained based on the values in Table 6 was 31,2 L/d. Fixture Table 6 Calculation of Water Consumption by Fixture Method No. of fixture N Unit water consumption q [L/(use/unit)] Maximum number of use per hour [times/h] (2) Calculation of water consumption based on proposal basic unit Maximum water consumption per hour Q hm [L/h] WC ,48 Urinal Wash basin ,48 Cleaning sink Water faucet in hot water supply room Faucet Lawn faucet Total ,8 Maximum expected water consumption per hour 7,8 7,8 Q hm [L/h] Average expected water consumption per hour 7,8/2 3,9 Qh[L/h] Daily water consumption Qd[L/d] 3,9 8 31,2 Based on water consumption per use by fixture type (conventional basic fixture unit) used in (1), water consumption appropriated for water saving plumbing fixtures (proposal basic unit q ) was determined. As the flush volume of urinals installed in the target building is 2.8 L/use, and that of WCs is 4.8 L, we proposed that q of WC used in the calculation be changed from 1 L/use to 4.8 L/use and that of urinal from 3 L/(use/unit) to 2.8 L/(use/unit). Water consumption of wash basin (water supply discharge volume) by gender calculated from flow rate and average discharge time spent using wash basin by gender are shown in Table 7. Water consumption of men s wash basin was.25 L/use, that of women s was.46 L/use. q of water basin was set to.5 L/(use/unit) as it was necessary to set the value of q larger than the consumption of women s wash basin. Table 7 Proposed basic fixture unit of wash basin Wash basin Men s Average flow rate * L/min 2.5 Average discharge time 3) [s] Water consumption [L/(use/unit) 6.25 Women s Comment)*: Provided by TOTO LTD. Proposal basic unit q`[l/(use/unit) Newly determined q of sanitary fixtures are shown in Table 8. Calculation was made by the same method as (1), and as a result daily water consumption of 1,512 L/d was obtained

7 Fixture Table 8 Calculation of water consumption by fixture method (Using proposal basic unit) No. of fixture N Unit water consumption q [L/(use/unit)] Maximum number of use per hour [times/h] Maximum water consumption per hour Q hm [L/h] WC ,67 Urinal Wash basin Cleaning sink Water faucet in hot water supply room Faucet Lawn faucet Total - - 2,628 Maximum expected water consumption per hour 2,628 2,628 Q hm [L/h] Average expected water consumption per hour 2,628/2 1,314 Q h [L/h] Daily water consumption Q d [L/d] 1,314 x 8 1, Comparison of Water Meter Data and Values Obtained by Calculation Method Based on Design Criteria Comparison of average water consumption per day obtained from the water meter data with the values calculated from the calculation method of the design criteria is shown in Figure 5 and Table 9. Water consumption [[L/d] 5, 4, 3, 2, 1, 5,833 Water meter data 43,6 Personnel method 31,2 Fixture method (traditional values) 1,512 Fixture method (proposed values) Figure 5 Comparison of daily water consumption From Figure 5, it can be seen that the results obtained using basic fixture unit appropriate for water-saving sanitary fixtures were closer to the water meter data than the results obtained by the conventional calculation method in the design criteria were. Comparison of the results by the personnel method and fixture method with the water meter data revealed that those by the personnel method were 7.6 times, those by the fixture method were 5.4 times overestimated. However, the results obtained by the 535

8 fixture method using basic fixture unit appropriate for water saving plumbing fixtures were 1,8 times, the closest to the water meter data. Table 9 Results by each estimation method and water meter data Type Facilities design criteria of MLIT Water meter data Fixture method (traditional Fixture method Personnel values) (proposed values) Q hm [L/h] - 1,9 7,8 2,628 Q d [L/day] 5,736 43,6 31,2 1,512 Magnification factor of Q d against water meter data Calculation by MSWC MSWC calculates water and hot water load of each fixture on the second time scale on a personal computer by using Monte Carlo technique based on a load calculation model consisting of average values and distributions such as fixture usage frequency, number of usage, time, consumption of water and hot water 3) 4). 4.1 Conditions of Simulation Simulation of water consumption in the target building was carried out using the load calculation model. Conditions adopted in the simulation are shown in Table 1. Fixture Table 1 Conditions of Simulation Men s WC Men s urinal Men s wash basin Women s WC Women s wash basin No. of fixture Distribution diagram of average water supply discharge time (Exp:-1 Hyp:1 Erl:) -1-1 Distribution diagram phase of average water supply discharge time Average water supply discharge time (second/use) Distribution form of average water supply discharge volume (Exp:-1 Hyp:1 Erl:) Distribution form phase of average water supply discharge volume Average water supply discharge volume[l/min] Distribution form of occupancy time (Exp:-1 Hyp:1 Erl:) 1 1 Distribution form phase of occupancy time Average occupancy time (second/person) Increase of usage with multiple use taken into account No. of people, house, room Usage frequency per day (use/house/day) Fixture usage rate (Ratio of water to hot water) Usage temperature[ ] The WCs installed in the target building are the hybrid type with flush volume of 4.8 L equipped with small tanks. Water consumption is regulated to be 12 L/min. by constant 536

9 flow regulating valves and capacity of small tanks is determined to be 3 L. Taking these into consideration, average water supply discharge volume and average water supply discharge time were set as 12 L/min. and 15 seconds respectively. Number of personnel was obtained by multiplying the floor space of the office room by an efficacy rate.2. Male-to-female ratio was 7: Results of Simulation Simulated values of water supply flow rates for 1 seconds, 1 minute, 1 minutes and 6 minutes are shown in Figure 6. Water consumption [L/1sec] : 12: 18: Water consumption [L/min] seconds 1 minute 6: 12: 18: Water consumption [L/1min] ,5 1 minutes 1,2 1 hour 6: 12: Time[h] 18: Water consumption [L/h] : 12: Time[h] 18: Figure 6 Simulated water consumption values It can be seen that water consumption increased near business opening hours, before and after lunch, and near closing hours. It tended to reach maximum particularly before and after lunch. Maximum water consumption per day was L/day. Maximum water consumption at the measurement time scale from 1 seconds to 1 day is shown in Table 11. Table 11 Maximum water consumption at each measurement time Measurement time 1seconds 1minute 1minutes 6minutes 1day Maximum water consumption [L] , ,948.8 Q hm and Q d used for comparison with the calculation results of water meter data and design criteria data were L/h and L/day respectively. 537

10 4.3 Comparison of Calculation Results of Water Meter Date and Design Criteria Data with Results of MSWC Average water consumption per business day, values calculated by the calculation method of design criteria and simulated values are shown in Figure 5 and Table 12. In contrast to water meter data and the calculation method of design criteria, MSWC, as seen in Figure 5, made it possible to predict average water consumption per day in the target building. The magnification factor of 1.3 was obtained when the calculation method of the design criteria and values estimated by MSWC were compared with water meter data. It is confirmed that comparable level of prediction can be made by the both methods. Water consumption[[l/d] 5, 4, 3, 2, 1, 5,833 Water meter data 43,6 Personnel method 31,2 Fixture method (traditional values) 1,512 7,949 Fixture method (proposed values) MSWC Figure 5 Comparison of daily water consumption Table 12 Magnification factor of each estimated value against water meter data MLIT Water Type meter Fixture method Fixture method MSWC Personnel data (traditional (proposed method values) values) Q hm [L/h] - 1,9 7,8 2,628 1,141 Q d [L/day] 5,736 43,6 31,2 1,512 7,949 Magnification factor of Q hm against MSWC values Magnification factor of Q d against water meter data Conclusion In this study we intended to propose basic fixture unit for the calculation method of the design criteria, and conducted fundamental study for establishing a water supply system based on MSWC. The results can be summed up as follows: 1) In applying the calculation method of the design criteria, the use of conventional basic fixture unit leads to overestimation. On the other hand, the use of basic fixture unit suited to a water-saving fixture makes it possible to predict values closer to the actual water consumption. 538

11 2) Compared with the values obtained by the calculation method of the design criteria, MSWC enables to predict values closer to actual water consumption. For future research, we are planning to carry out actual measurements in the target building and take a comparison of peak flow rate of water supply between the calculation method of SHASE-S 26 and the actual value, then we will propose a basic unit due to the calculation method of SHASE-S 26 depends on the actual value. Acknowledgment We would like to express our gratitude to Mr. Konosuke Matsushita of TOTO for providing us with technological assistance for our proposal basic unit. References 1) Ministry of Land, Infrastructure, Transport and Tourism, Facilities Design Criteria, 26 2) The Society of Heating, Air-Conditioning and Sanitary Engineers of Japan, SHASE- S26-29, 29 3)Takadta H., Murakawa S., Yamane Y., Sakamoto K.(26), Calculation of The Cold and Hot Water Supply Demands in Office Building, J.Environ.Eng.,AIJ,No.66,pp )Sakamoto K., Murakawa S., Koshikawa Y., Takata H.(27),Evaluation for Booster Pump System in Office Buildings, J.Environ.Eng.,AIJ,No.622,pp Presentation of Author(s) Guangzheng Wu He is a graduate student at the Sakaue laboratory, Department Of Architecture, School of Science and Technology at Meiji University in Japan. Kyosuke Sakaue (Dr. Eng.) is a professor at Department of Architecture, School of Science and Technology, and a head of New Plumbing System Institute, Meiji University. His fields of specialization include water environment, building services and plumbing system. 539

12 CIBW62 Symposium 213 Kuniharu Kojima Dr.Eng. Lecturer at Meiji University Registered Consulting Engineer Japan Registered 1st Class Architect Kazuya Fujimura is a mechanical engineer at Mitsubishi Jisho Sekkei Inc. Japan. He is engaged in research / development of drainage plumbing system. Saburo Murakawa (Dr. Eng.) Professor at Hiroshima Univ. Japan. He is engaged in Architecture and building engineering / Architectural environment/equipment Kazuo Hayakawa is a mechanical engineer at Toda Corp.,Japan. He is engaged in research / development of drainage plumbing system. 54