CIBW062 Symposium 2012

A Study on the Evaluation of a Super Water-Saving in Regard to the Drainage Performance thereof in the House Drain Section

Naofumi Kobayashi (1), Masayuki Otsuka(2) 1. [email protected] 2. [email protected] 1. Graduate student, Graduate School of Engineering, Kanto-Gakuin Univ. 2. Department of Architecture College of Engineering, Kanto-Gakuin University, Dr. Eng,

Abstract Toilet efficiency in conjunction with water conservation has been promoted worldwide, but this unfortunately often diminishes the drainage performance in the large-diameter house drain section of drainage systems, causing waste materials, toilet , etc. to block the house drain, as reported at the International Symposium of CIB W062. In Japan, 6-litre flush which were mainstream a few years ago have been gradually taken over by super water-saving toilets which use much less water and are becoming more available on the market.

This paper examines, through experiments, how the drainage performance of the house drain is affected by employing different types of super water-saving toilets, including those using less than 6 liters of water, in consideration of various factors, such as the type of waste material (substitute), the toilet drain height, and the condition of drainage flow.

Keywords Super water-saving toilets, House Drain,

1 Background of the study Toilet water conservation has been promoted worldwide, and 4.8-litre toilets are available in the West Coast of America. However, toilets using less water can diminish the carrying performance of the house drain of drainage systems, as pointed out at the International Symposium of CIB W062. Fig. 1 shows the trend of toilet water conservation in Japan in relation to standards and specifications. In Japan, 6-litre toilets have been used since 1999, and in 2011, 4-litre toilets became available in the market.

277

CIBW062 Symposium 2012

At present, even more efficient, 3.8-liter toilets are commercially available. Water-saving are currently classified into type I and type II, depending on the type of flushing system and the amount of water used for flushing (see Table 1), in accordance with Japan Industrial Standards (JIS). At the International Symposium of CIB W062, it was reported that in Taiwan, the application of water-saving toilets diminished the carrying performance of the house drain of drainage systems1)2). Subsequently, this report evaluates the carrying performance of the house drain when waste substitutes are drained from different heights through a drainage stack system which is equipped with a 4-litre super water-saving toilet. Furthermore, based on the assumption that the downward flow of drainage water and waste in the drainage stack affects the carrying performance of the house drain, this report clarifies the relationship between the carrying performance of the house drain and the drainage characteristics at the base of the drainage stack.

13L

10L

flush water flush Transitionof ofamount the 8L 6L 5L 4.8L 4L 3.8L 1990～ 2000～ 2010～

BL Standards Methods of Testing Performance of Apr. 1999 Jul. 2006 Jan. 2011 Quality Housing Components Waste substitutes Waste substitutes Waste substitutes BLT WC:2010 PVA sponge 2 Roll of paper 6m Lay flat paper 3.6m (The Center for Better Living) Balled-up paper 4 JIS A 5207 Sanitary wares Jan. 2011

(Japan Industrial Standards) Formulation of water-saving and specifications and Related standards Related type Ⅰand type Ⅱ Other Overseas regulations 1992～ 2011 Regulations on 6-litre flush Regulations on 4.8-litre flush toilets toilets （Some parts of the US） Energy Policy Act(USA) California Environmental Protection Agency regulations Fig. 1 Trend of toilet water conservation and related standards and specifications Table 1 JIS classification of water-saving toilets Classification Cistern Flush valve Type I 8.5[L] or less 8.6[L] or less Type II 6.5[L] or less 8.5[L] or less*) *)Type II/flush valve: limited to specific-type toilets with a flush valve

2 Objective of the study Using an experimental tower which simulates a typical drainage system for high-rise buildings, this study discusses the following points about the carrying performance of the house drain: (1) Clarify the relationship between the toilet drain height and the distance waste substitutes are transported in the house drain. (2) Examine the toilet drain height and the variation of the drainage characteristics measured in the base part of the drainage stack

278

CIBW062 Symposium 2012

3 Outline of the experiment (1) Experimental systems (A) House drain carrying performance experiment This experiment employs a high-rise simulation tower of Kanto Gakuin University, which has nine storeys and a height of 25m. Fig. 2(a) shows the stack system used for this experiment. The stack system is of a vent type and comprises a drainage stack with a diameter of 100A (with JIS-DT fittings attached thereto), and horizontal fixture branches with a diameter of 75A (pitch 1/100). The diameter of the house drain is 125A (pitch 1/150), and the length thereof is 18m with reference to the previous report2) presented at CIBW62 in 2011. In (a) the house drain carrying performance experiment, a super water-saving, 4-litre toilet is used, and a drainage load is applied from the 1st to 8th floors respectively. Incidentally, there are two types of drainage loading: a large amount of flush water for draining solids (full flush) and a small amount of flush water for draining (partial flush). As waste substitutes are drained from each floor, the distance they are transported in the house drain is measured.

(B) Stack drainage characteristics experiment This experiment uses a stack comprising a large inlet installed at the base of the stack, and the characteristics of a downward flow in the stack are measured. Fig. 2(b) shows the stack system used for this experiment. In (b) the stack drainage characteristics experiment is implemented from the 1st, 3rd, 6th and 9th floors which provide typical drainage loading conditions.

Bellmouth Vent section: bellmouth Horizontal branch: diameter 75A pitch 1/100 Stack: diameter 100A House drain: diameter 125A pitch 1/150

House drain connection points (flanges and sockets): 1.5, 3, 4, 6, 7, 9, 13, Power and 17m from the amplifier stack Low-pass filter Increaser A/D converter 100×125 PC

(a) House drain carrying (b) Stack drainage characteristics performance experiment experiment Fig. 2 Experimental stack systems

279

CIBW062 Symposium 2012

(2) Discharge Characteristics of Toilets Fig. 3 shows curves representing the discharge characteristics of the toilet used in the experiments. The curves are of discharge volumes, discharge flow rates, etc. which were recorded when the full flush and the partial flush were used. Meanwhile, Table 1 lists the values of the discharge characteristics of the toilet. Incidentally, a 4[L] toilet was used in the experiments, and the discharge characteristics thereof were measured in accordance with SHASE-S 220-2010, “Testing Method of Discharge Characteristics for Plumbing Fixtures”. The average discharge flow rate, qd, is one of the indices representing the discharge characteristics of plumbing fixtures, and a qd value is obtained by measuring a discharge flow rate while 20-80% of flush water is discharged from a toilet and dividing the discharge flow rate by the discharge time. Table 1 also lists the discharge characteristics of a 6-litre water-saving toilet for comparison. Table 2 indicates that although the 4-litre toilet used in the experiments uses less flush water, the average discharge flow rate, qd, and instantaneous maximum discharge flow rate thereof are greater than those of the 6-litre toilet. This suggests that a high discharge flow rate compensates for a small amount of flush water so that the discharge performance of a toilet does not have to be compromised.

2.5 10 2.5 10

Discharge flow rate ]

qmax ] Discharge volume

L

L

[

[ [L/s] [L/s] 2.0 8 2.0 8 qmax td 1.5 6 1.5 6

1.0 80% 4 1.0 4

0.5 0.6W 2 0.5 2

20%

Discharge volume Discharge

Discharge volume Discharge Discharge flow rate flow Discharge Discharge flow rate flow Discharge 0.0 0 0.0 0 0 5 10 15 20 0 5 10 15 20 Measurement time [sec] Measurement time [sec] (1) Full flush (2) Partial flush

Fig. 3 Discharge flow rate curves and discharge volume curves

Table 2 Discharge characteristic values

Avg. Instantaneous Avg. discharge flow rate Discharge Discharge discharge max. discharge with the drain pipe flow rate time flow rate flow rate connected Type of flush W[L] td[s] qd[L/s] qmax[L/s] qd'[L/s] Full flush 4.2 1.2 2.23 2.39 2.01 Partial flush 3.7 1.2 1.88 1.91 - 6L(Full flush) 6.0 1.9 1.93 2.11 - * The length of the horizontal branch with the drain pipe connected: 1m

280

CIBW062 Symposium 2012

(3) Waste substitutes for the experiments Table 3 and Fig. 4 show the waste substitutes used in the house drain carrying performance experiment. Waste substitute D is a 1m-long piece of paper (1 ply) which is folded into six layers, and waste substitute D’ is a 1m-long piece of paper (2 ply) which is also folded into six layers. Furthermore, new waste substitute BL is a 0.9m-long piece of paper (1 ply) which is folded into four layers, and this is in accordance with a BL (Better Living) standard, “Methods of Testing Performance of Quality Housing Components” which was formulated in 2011 by the Center of Better Living. In addition, in order to compare with the outcome obtained from the study in Taiwan, two pieces of PVA sponge were also used in the experiments for reference.

Table 3 Waste substitutes for the experiments Waste substitute Description D Lay-flat , 6m (1 ply) D' Lay-flat toilet paper, 6m (2 ply) NewBL Lay-flat toilet paper, 3.6m (1 ply)

PVA sponge PVA sponge, 2 pieces * New BL: “Methods of Testing Performance of Quality Housing Components” BLT WC:2010 by the Center of Better Living

(1) Waste substitute D (2) Waste substitute D’

50

40

30

20 10

0 [mm]

(3) Waste substitute New BL (4) Waste substitute PVA sponge Fig.4 Waste substitutes for the experiments (4) Transport Distance in the House Drain As shown in Fig. 5, the transport distance in the house drain is from the core of the stack to the very last waste substitute which is held up in the transport direction in the house drain. The transport distance was measured five times using waste substitute D, and twice with the other types of waste substitutes respectively. The average transport distance in relation to each type of waste substitute will be described later.

Fig. 5 Transport distance in the house drain 281

CIBW062 Symposium 2012

4 Results and Consideration 4.1 House drain carrying performance experiment (1) Comparison of transport distances by full flush and partial flush Fig. 6 shows the relationship between the floor height from which draining is performed and the transport distance measured in the house drain. Fig. 6 first shows respective transport distances after the first full flush, and then shows respective transport distances after the subsequent, partial flush. The change of each transport distance is indicated by an arrow. Fig. 6 also shows, for reference, the values obtained from a drainage experiment, which used a 6-litre toilet and which was carried out from the 15th floor of an experimental tower of the Urban Renaissance Agency, and the average length of the house drain applied to actual buildings in Taiwan. In relation to waste substitutes D, D’ and New BL, the transport distance becomes longer as the drainage load becomes smaller, i.e. New BL (smallest load), D, and D’ (largest load). As for the transport distance with the PVA sponge, when comparing to the transport distance measured in the experiment described in the previous document1), which employed a drainage system similar to the one in this experiment, a decrease of approx. 50% in the transport distance was obtained from this experiment using a smaller volume of flush water and a larger house drain diameter. In addition, the transport distances of waste substitutes D, D’ and New BL all became shorter when draining was performed from upper floors (the 6th, 7th and 8th floors) and lower floors (the 1st and 2nd floors) than from intermediate floors (the 3rd and 4th floors).

Table 4 summarises the differences in the transport distances between when measured using a full flush and when measured using a partial flush subsequently, as shown in Fig. 6. When paper waste substitutes were used, the average transport distance was longer than 10m. When waste substitute D’ was applied with a partial flush, the transport distance was longer than the transport distance when waste substitute D was applied. This suggests that a large volume of waste holds back a large amount of water.

9 Avg. house drain length 17.2m for buildings in 2) 8 Taiwan (Reference ) 7 6 Transport distance 8m or more (Reference3) 5 6L flush water (Waste B (D in the rolled )) 4 3 Avg. transport distance 2 8.2m (±2.9m) 1 0 0 3 6 9 12 15 18 Transport distance [m] (1) Waste substitute D Fig. 6 Drain heights and transport distances of different waste substitutes

282

CIBW062 Symposium 2012

9 8

7 As in (1) 6 5 4 3

2 Avg. transport distance 1 5.9m (±2.4m) 0 0 3 6 9 12 15 18 Transport distance [m] (2) Waste substitute D' 9

8 7 6 5 4 Avg. transport distance 3 13.9m (±3.7m)

2 As in (1) 1 0 0 3 6 9 12 15 18 Transport distance [m] (3) Waste substitute New BL 9 8 Avg. transport distance 7 3.9m (±0.8m) 6 Standard 5 transport distance (Reference1)) 4 8.7m (±0.8m) 3 Flush water volume 6L 2 House drain φ100 1 1/100 0 0 3 6 9 12 15 18 Transport distance [m] (4) Waste substitute PVA sponge Fig. 6 Drain heights and transport distances of different waste substitutes

Table 4 Transport distances of different waste substitutes (full flush ⇒ partial flush) Avg. distance±standard deviation [m] Waste substitutes Full flash ⇒ Partial flush D 8.2 (±2.9) ⇒ 14.1 (±3.9) D' 5.9 (±2.4) ⇒ 14.2 (±4.0) New BL 13.9 (±3.7) ⇒ 16.9 (±2.7) PVA sponge 3.9 (±0.8) ⇒ 4.2 (±1.1)

283

CIBW062 Symposium 2012

(2) Waste substitutes and the flow characteristics of drainage in the stack The transport distances of waste substitutes D, D’ and new BL were respectively shorter when draining was performed with a full flush from upper floors and lower floors than from intermediate floors. The cause was considered to be related to how paper and clean water was mixed together. Fig. 7 (1) shows different time durations from draining is started, using a mixture of clean water (D or D’) and paper (D or D’), until the drainage flow first reaches the base part of the stack. Fig. 7 (2) shows the time lags calculated from the time durations in (1). Fig. 7 (1) indicates that when draining is performed from the 3rd floor upwards, the waste substitute contained in the drainage reaches the base part of the stack before the clean water, and when draining is performed from floors below the 3rd floor, the order of the drainage contents reaching the base part of the stack reverses. When draining is performed from the upper floors, the paper and the water in the drainage become separated while flowing down in the stack. Furthermore, the flow rate of the drainage from the upper floors decreases gradually as the drainage flows down the stack. As for the drainage from the lower floors, because the water flows down ahead of the paper, the amount of water for pushing the paper decreases. These findings suggest that the drainage from the upper floors and the lower floors resulted in creating shorter transport distances than from the intermediate floors, as shown in Fig. 6.

[m] [F] Time lag(D) 20 8 Paper（D） 7 Paper(D') Time lag(D') 6 Water(D) 5 Water(D') 10 4 3 Stack flow rate 2 approx. 2.5 0.6 1

0 1 2 3 4 5 6 7 8 9 1011121314 [s] -3 -2 -1 0 1 2 3 4 5 6 [s] (1) Free-fall time of water/waste (2) Time lags substitute-containing drainage Fig. 7 Water/waste substitute-containing drainage in relation to the free-fall time thereof

284

CIBW062 Symposium 2012

(3) Reality involving drainage conditions and drainage systems Here, Fig. 8 shows a typical drainage system for apartment houses in Japan. In Japan, the drainage piping branches out to connect to different plumbing fixtures, and therefore, the drainage from all the fixtures all goes into one house drain. Such being the case, when accommodating super water-saving toilets, as shown in Fig. 8, the transport distance of the drainage received in the house drain from the toilets is an important factor.

Furthermore, the previous document3) describes a questionnaire survey about the recent awareness among people about the use of toilets and how they actually use their toilets, and on the basis of the survey results, Fig. 9 shows a daily drainage pattern. According to Fig. 8, full flushes are intensively used during morning hours, and partial flushes are used averagely during the day. Obtained from all the results are: the average number of toilet events per person per day is excrement 1.1 times and 5.2 times. The average number of washing is 0.4 times.

These findings support that the transport distance of paper in the house drain exceeds 10m when a full flush is operated followed by a partial flush, as explained earlier, and it would be possible to transport drainage in the house drain adequately even by using a 4-litre toilet.

4 Full flush

3 Partial flush

2

No. ofNo. flushes 1

0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time [h] Fig. 9 Daily drainage pattern obtained from the previous document

Fig. 8 Typical drainage system for apartment houses in Japan

285

CIBW062 Symposium 2012

4.2 Understanding the characteristics of drainage flowing in the stack As described in 5.1 (2), it is considered that the transport distance of waste substitutes in the house drain is affected by the variation of the flow rate and volume of drainage flowing down in the stack. Fig. 10 shows how the characteristics of drainage, which is from the 1st to 8th floors, vary when measured at the base part of the stack. On the basis of this and in accordance with SHASE-S220, the variation of the flow rate of fixture drainage, qds’, per floor was measured, when connected to the stack, which is shown in Fig. 11 also shows the drain height in relation to the qds’ value, indicating that the higher the floor level, the smaller the qds’ value, and that the qds’ value of the drainage from the 8th floor is significantly smaller than that of the drainage from the 1st floor. Incidentally, the flow rate of clean water from a height of approx. 20m was approx. 0.1[L/s].

2.5 5.0 Discharge flow 1F 2.0 rate 4.0 1.5 3F 3.0

1.0 6F 2.0 Discharge

0.5 8F volume 1.0

Drainage volume Drainage [L] volume Drainage Drainage flowrate [L/s] 0.0 0.0 0 5 10 15 20 25 Measurement time [s] Fig. 10 Volume and flow rate of drainage

2.5 [L/s] 1F 1F （0.6m) 2.00 [L/s] 2.0 3F （7.4m) 0.74 [L/s] 6F （16.4m) 0.15 [L/s] 1.5 8F （22.4m) 0.07 [L/s] 1.0 3F 0.5

6F 8F (when connected (when to connected stack)

Avg. fixture discharge rate flowdischarge Avg. fixture 0.0 qds' 0 5 10 15 20 25 Flow distance in the stack L[m] Fig. 11 Average fixture discharge flow rate qds’ when connected to the stack

286

CIBW062 Symposium 2012

5 Summary and Conclusions Subsequent to the experiments using the drainage stack system of a 9-storey high-rise building, which is equipped with a 4-litre super water-saving toilet and JIS-DT fitting, the following knowledge has been acquired:

1) The relationship between the drain height and the transport distance of waste in the house drain has been understood through the house drain carrying performance experiment. The average transport distance of waste substitute D was approx. 8m with drainage loading from all the selected floors.

2) Assuming a real usage situation, when a full lush was applied followed by a partial flush, the average transport distance of paper (waste substitute) was longer than 10m.

3) By draining clean water from the floors, the characteristics of drainage in the base part of the stack were understood; as the drain height increases, the flow rate of the drainage in the base part of the stack decreases. The flow rate of clean water applied from a height of approx. 20m was approx. 0.1[L/s].

Acknowledgement This study is partially supported by “A Study on a Drainage System that Enables Free-plan Housing Technology (Masayuki OTSUKA et al.)”, Ministry of Education, Culture, Sports, Science and Technology, 2009 Grants-in-Aid for Scientific Research (c), Research Number 21560621.

References 1） C.L. Cheng: Research of main drain system and solid transportation performance in existing buildings, CIB W62 36th International Symposium（2010.10） 2） C.L. Cheng: Simulation of solid transportation and regulation for drain system in Taiwan, CIB W62 36th International Symposium（2011.9） 3） OGAWA Haruhisa et al.: Experimental study influences on drainage stack system by the super water saving toilets (part 1) Discussion regarding method drainage characteristic and drainage carrying, Transactions of the Society of Heating, and Sanitary Engineers of Japan (20011.9) 4） MOROKAWA Mari et al.: Study on the actual condition of toilet use –The consciousness and the act to use based on a questionnaire-, Transactions of the Society of Heating, Air Conditioning and Sanitary Engineers of Japan (2010.9) 5） SHASE-S 220-2010: “Testing Method of Discharge Characteristic for Plumbing Fixtures” by the Society of Heating, Air Conditioning and Sanitary Engineers of Japan 6） SHASE-S 206-2009: Plumbing Code by the Society of Heating, Air Conditioning and Sanitary Engineers of Japan

287

CIBW062 Symposium 2012

Presentations of Authors

Naofumi Kobayashi is a master of the Otsuka laboratory, Kanto Gakuin University. He is a member of AIJ (Architectural Institute of Japan) and SHASE (Society of Heating, Air-Conditioning and Sanitary Engineers of Japan). His current study interests are the drainage performance improvement technique of loop vent system and the Evaluation of a Super Water-Saving Toilet in Regard to the Drainage Performance thereof in the House Drain Section.

Masayuki Otsuka is the Professor at Department of Architecture, Kanto Gakuin University. He is a member of AIJ (Architectural Institute of Japan) and SHASE (Society of Heating, Air-Conditioning and Sanitary Engineers of Japan). His current research interests are the performance of plumbing systems, drainage systems design with drainage piping systems for SI (Support and Infill) housing, development of building energy simulation tool（BEST）and the performance evaluation of water saving plumbing systems.

288