Characteristics and Current Status of Drainage System with Special Fitting

Transcription

1 CIBW0 Symposium 0 Characteristics and Current Status of Drainage System with Special Fitting Kyosuke Sakaue (), Masayuki Ostuka (), Michihiro Koike (), Takayuki Toyama (). sakaue@isc.meiji.ac.jp. dmotsuka@kanto-gakuin.ac.jp. Michihiro_Koike@haseko.co.jp. takayuki.toyama@kubota.com () Dept. of Architecture, School of Science and Technology, Meiji University, Japan () Dept. of Architecture, College of Engineering, Kanto Gakuin University, Japan () Technical Research Institute, HASEKO Corporation, Japan () KUBOTA Corporation, Japan Abstract There are three types of vent systems that are commonly used in a drainage system. The stack vent system exclusively relies on stack vents while the horizontal branch vent system utilizes vent stacks and branch vent pipes, and the individual vent system makes use of individual vent pipes in addition to vent stacks and branch vent pipes. In terms of reducing pneumatic pressure in drain, which causes induced siphonage, the stack vent system fall behinds the horizontal branch vent system and the individual vent system. However, the stack vent system with special drainage fittings (referred to as the drainage system with special fitting below) has been proven equal to the horizontal branch vent system and the individual vent system in reducing pneumatic pressure in drain. The paper presents the background information on the development of the drainage system with special fitting, and sheds some light of its drainage and ventilation characteristics, which were examined on the basis of the data obtained through discharge experiments using an experimental tower. The system demonstrated superior ventilation performance against negative pressure, but was found insufficient against positive pressure produced at the bases of drainage stacks. The construction cost for the system is relatively low and the venting performance is good, but the types of building to which it can be applied are limited.

2 CIBW0 Symposium 0 Keywords Drainage system; stack vent system; special drainage fitting; pressure characteristics Introduction There are three types of vent systems that are commonly used in a drainage system. The stack vent system exclusively relies on stack vents while the horizontal branch vent system utilizes vent stacks and branch vent pipes, and the individual vent system makes use of individual vent pipes in addition to vent stacks and branch vent pipes. The stack vent system with special drainage fittings is a simple, low-cost system having ventilation capacity (performance to reduce pressure) equal to the branch vent system and individual vent system. In Japan, the stack vent system is generally adopted in apartment houses and hotels where the number of fixtures connected to branch pipes is small. In other buildings such as office buildings the loop vent system is mainly used. There are two types of drainage stack fittings (fittings used for connecting stack with horizontal branches or fixture drains): JIS drainage fitting (referred to as JISF below) and special drainage fitting (referred to as SDF below). While JISF is used with the loop vent system, and with the stack vent drainage system in seven-story or lower buildings, SDF is used with the drainage system in eight-story or higher buildings. The stack vent drainage system using SDF is called the special drainage fitting system (referred to as SDF system below). The SDF system has been developed in Japan. The current paper focuses on the background of its development, presents drainage performance tests and considers characteristics of pressure in drain. Development of SDF System. Drainage system and vent system Drainage systems currently used all over the world date back to the mid th century. During the Industrial Revolution in Great Britain the prototype was created based on the principles of gravity transportation and water sealed traps. Gravity transportation followed in the wake of the sewage transportation system that had been in use at the time. As for the water sealed trap, the one that was adopted in then newly developed WC began to be used in the drainage system as well. However, water sealed trap was later found to be defective in that seal break due to induce siphonage, self-siphonage or evaporation occurred frequently. For this reason, a vent pipe became a must item to go with a drainage system to reduce pressure in drain (referred to as pressure below) that was found to cause induced siphonage. The vent systems currently used around the world can be broken down into the following three types as shown in Figure. In the individual vent system, individual vent pipes are installed in the fixture drain of each trap to decrease pressure. The

3 CIBW0 Symposium 0 Stack vent system Branch vent (Loop) system Individual vent system Figure - Vent system individual vent vent pipes are installed in the fixture drain of each trap to decrease pressure. The individual vent pipes are connected to horizontal branches and vent stacks. This method is also called the fully vent system, and has been adopted as the standard in the U.K. and U.S.A. The branch vent system utilizes branch vents and loop vents in each horizontal branch connected to stack vents. This system has been in use in Europe, U.S.A. and Japan, and called the loop vent system in U.S.A. and Japan. The stack vent system utilizes stack vents exclusively. Stack vents are installed in drainage stacks to reduce the pressure. This system is currently used all over the world. The individual vent system and the branch vent system are equal in their performance to reduce pressure, and capable of preventing induced siphonage. The stack vent system lags behind in its ability to reduce pressure, and cannot be installed in high-rise buildings where large a discharge load is expected. By contrast, the stack vent system is far superior to others in terms of construction cost and piping space, followed by the branch vent system and individual vent system.. SDF System.. SOVENT system and SEXIA system The construction of high-rise buildings of -story or more has started in Europe since the latter half of the 0s. As the traditional stack vent system failed to achieve sufficient reduction in pressure, the branch vent system began to be adopted, and research into high-performance stack drainage system with stack vent system started in France and Switzerland. Discharged water in drainage stack forms annular flow and the retention of air flow in its core section holds a key for good ventilation in stacks. Some stack fittings with special structures have been developed to retain core ventilation and to change

4 CIBW0 Symposium 0 discharge flow. SOVENT fitting developed in Switzerland consists of a separate type stack fitting as shown in Figure and a base fitting to be connected to the horizontal main drain. The separate type stack fitting makes it possible to join the discharge flow in stack and that in horizontal branch into a single smooth flow, and the base fitting has a local vent passage that can reduce excess pressure accumulated in the base of drainage stack. SEXIA system utilizes stack fitting with guide feather to make the discharge flow inside stack to form turning flow as shown in Figure. Though SOVENT systems are currently being manufactured in Switzerland and China, no sufficient performance evaluation has been made in China. SEXIA systems have been improved in Japan, but are not manufactured in other countries. Partition plate Feather ling Guide feather SOVENT fitting SEXIA fitting Figure - SOVENT fitting and SEXIA fitting.. Drainage system with special fitting in Japan The plumbing system in Japan was modernized after the Second World War in accordance with National Plumbing Code in America, and the first design standard for the plumbing system, HASS 0 (current SHASE 0) was published in. While the stack vent system was generally used in low buildings, the loop vent system, which was simpler than the individual vent system, was adopted in high-rise buildings. The construction of -story apartment buildings started in, and the stack vent system was used. Apartment buildings of -story or higher began to be constructed since the latter half of the 0s. SOVENT system and SEXIA system were introduced to Japan in the late 0s and early 0s, and some performance evaluation tests were conducted by Japan Housing Corp. (current Urban Renaissance Agency). The systems analogous to SEXIA system ware also developed. These SDF systems made their way into plumbing systems in hotels as well as in apartment buildings. Experimental research on the characteristics of pressure and seal loss in the stack vent drainage system using JIS drainage fitting (general drainage T fitting, referred to as JISF below) analogous to SEXIA system was also developed. These SDF systems made their way into plumbing systems in hotels as well as in apartment buildings. Experimental research on the characteristics of pressure and seal loss in the stack vent drainage system using JIS drainage fitting (general drainage T fitting, referred to as JISF below) or SDF started in universities in the late 0s. From the 0s through the 0s, the

5 CIBW0 Symposium 0 Photo - Experimental tower Photo - Experimental tower ( stories, KUBOTA Co.) ( stories, m, URA) B fitting C fitting A fitting Figure - Representative SDF in Japan

6 CIBW0 Symposium 0 number of SDF makers grew to be eight. They strove to improve their technological expertise backed up by theoretical and experimental research at academic institutions. As a result, the technological level in the field improved tremendously. Photo shows one example of the experimental towers. The super high-rise experimental tower of URA is shown in Photo. The system began to be installed in super high-rise buildings in the 0s, and a high demand for performance evaluation arose. Based on extensive performance tests and theoretical research, SHASA-S Testing Methods of Flow Capacity for Drainage System in Apartment Houses was published in. There are mainly three types of drainage systems with special fittings on the market today. Their drainage stack fittings are shown in Figure. All of them are turning fittings, and made of cast iron. There are some B fittings that are made of fire-resistant plastic. Testing methods of Flow Capacity (SHASE-S ). Performance Criterion The process of seal loss inside trap due to induced siphonage can be outlined as shown in Figure. The pressure in drainage stack plays a crucial role in the plumbing system (fixture drain, horizontal branch, stack and building drain). The pressure in the stack vent system reaches its maximum negative pressure at one or two floors below the discharging floor and its maximum positive pressure at the lowest floor. The characteristics of pressure fluctuation are different depending on the fixtures drainage characteristics. For example, there is a distinct peak in WC drainage with pulsating wave patterns while drainage from bathtub typically produces sequential waves. As seal fluctuation is a response phenomenon produced by pressure fluctuation in drain, it is not easy to define the relationship between pressures in drain and seal displacement (the values of seal loss). However, some permissible values must be presented as a criterion in performance evaluation. We prepared the following stipulations. Discharge load Discharge flow rate [Characteristics of flow rate Pressure fluctuation maximum pressure [Shape of pressure wave] Seal fluctuation Seal loss [Characteristics of seal vibration] Figure - Process of seal loss.. Low-pass filtering of pressure We apply low-pass filters of Hz to measurements of pressure fluctuation in drain considering the fact that the natural frequency of trap seal water falls in the range about ~ Hz and that the response frequency of a pen recorder is about Hz. The

7 CIBW0 Symposium 0 maximum negative pressure and maximum positive pressures are taken as the representative values... Permissible seal loss and permissible pressure Though the minimum seal depth of trap is defined as 0 mm, the level of water retained in trap, that is, the residual seal depth (seal depth seal loss) should be used to evaluate the performance of seal water. However, seal depth differ depending on the type of trap, seal loss seems more appropriate as a standard index. So a half of the minimum seal depth, mm, was defined as the permissible seal loss. The permissible pressure in drain was determined to be ±00 Pa based on the fixed discharge flow load described in.. Pressure was measured along the horizontal branch at 00 mm from the drainage stack. Either the permissible seal loss or permissible pressure in drain was used as the criterion.. Discharge Load.. Constant discharge load Discharge load can be made in a short time with a large flow rate such as from a WC (referred to as fixture discharge flow below), or can last for some time with a constant discharge flow as made from bathtubs and combined discharge (referred to as continuous discharge flow below). Discharge load is determined by discharge flow rate. But as described in., the pressure from fixture load produces pulsating waves and that from continuous load produces sequential waves. When discharge loads (discharge flow rates) are the same, seal loss produced from continuous load (sequential waves) is greater than that produced from fixture discharge flow (pulsating waves). Fixture discharge load from multiple floors is unstable and it is difficult to select a representative fixture. Therefore it was not practical to use fixture discharge load as test load. In view of this we adopted constant discharge load that continues to discharge water at fixed flow rates... Loading method Given the same discharge load, the higher the floor from which discharge is made, the greater the pressure and seal loss. The pressure and seal loss are also greater when discharges from the adjacent floor are combined than when discharges from the floors that are apart from each other are merged. So in the test, discharge was made from the top floor and one floor below the top. The discharge load from an apartment consists of water flushed in WC and water from a kitchen sink; the maximum discharge load is estimated to be about. L/s. The maximum discharge load from a given floor in the test was also set at. L/s.. Test apparatus Water supply pipes were placed under drainage pipes so there wouldn t be any head produced when discharge load was applied. As this apparatus was made to measure pressures, it had short pipes to cover the specified pressure measurement points. The length of stack of each floor (floor height) was. ~.m. The piping layout of

8 CIBW0 Symposium 0 building drain was simplified (straight and m long with one size or larger diameters) since the method was meant to test the drainage performance of drainage stack. Pressure characteristics A stack vent drainage system with JISF (referred to as JISS system below), a loop vent drainage system with JISF (referred to as JISL system below) and an SDF system were constructed in the experimental tower shown in Photo. The diameter of the drainage stack was 0 mm, that of the building drain was mm. Discharge load was applied from the floors ~. Pressure measurements were made in these systems using the SHASE-S test method. The results of JISS system and JISL system are shown in Figure, and those of SDF system in Figure. The graphs on the left show minimum values, and those on the right show maximum values. The discharge flow rate in JISS system was.0 L/s and the maximum negative pressure was about 00 Pa. The vertical distribution of pressure shifted toward the negative side with high negative pressures seen on the middle floors. In JISL system, the discharge flow rate was.0 L/s and the maximum negative pressure about 00 Pa. The vertical distribution of pressure shifted toward the negative side with high negative pressures seen on the lower floors. The reason for this is that air flow was blocked by water membranes at the exit of the drainage stack. In JISL system for high-rise buildings the discharge flow rate was.0 L/s and the maximum negative pressure about 0 Pa. The vertical distribution of pressure also shifted toward the negative sides. In SDF system for super high-rise buildings the discharge flow rate was.0 L/s and the maximum negative pressure about 0 Pa. The vertical distribution of pressure spread over both positive and negative sides with no significant difference between middle floors and lower floors. The permissible discharge flow rates based on the permissible pressure of ±00 Pa were.0 L/s in JISS system,.0 L/s in JISL system, and.0 L/s or more in SDF system for high-rise buildings, and.0 L/s in SDF system for super high-rise buildings. These results indicated that JISS system was far inferior to the other two systems in its performance to reduce pressure while SDF system surpassed JISL system. Conclusion It can be said that SDF system was born in Europe, and grew up to be mature in Japan. In this process presenting a performance evaluation method, rather than settling on a design standard that would have been a mere collection of fixed stipulations seems to have played a crucial role in improving the system and acquiring the trust of the market. On average about 0,000 SDF systems have been sold per year since reaching the volume accumulation of about 0 million units. As the result of having done JISL system and SDF system evaluation for adoption in an apartment of 0 stories, the ratio of JISL system for SDF system became.. This track record itself is the proof of the high cost performance and superior pressure reducing capability of SDF system.

9 計測階 [ 階 ] CIBW0 Symposium 0.0 L/sec pressure [Pa]. L/sec pressure[pa].0 L/sec pressure [Pa] JISS system.0 L/sec 管内圧力 [Pa].0 L/sec presure [Pa].0 L/sec pressure [Pa] JISL system Figure - Vertical distribution of pressure in JISS system and JISL system

10 CIBW0 Symposium 0.0 L/sec pressure [Pa].0 L/sec presure [Pa] For high-raise buildings.0 L/sec presure [Pa] For super high-rise buildings Figure - Vertical distribution of pressure in SDF system

11 CIBW0 Symposium 0 As the technical examination problem, there is a problem associated with drainage of cleaning substance. In Japan each house is equipped with a washing machine. Detergent foam discharged from washing machines has been known to produce excessive positive pressure at the bottom of drainage stack. As it is difficult to prevent this from occurring, horizontal branches on the lowest floor are usually not connected to drainage stack. Recently it was found that discharging bath water that contained bath additive could cause excessive pressure. These problems merit further research in the future. Presentation of Authors Kyosuke Sakaue (Dr. Eng.) is a professor at Department of Architecture, School of Science & Technology, and a head of New Plumbing System Institute, Meiji University. His fields of specialization include water environment, building services and plumbing system. He is currently engaged in the studies of next drainage system, trap performance, WC, stainless steel piping, water saving systems, maintenance.