## 4 Data Analyses, Discussion and Findings  
### Prefabrication Scope Identification  
We divided questions into three groups to survey and discuss the level of the feasibility of piping prefabrication in different piping systems, different connection modes, and different types of project. The results are shown in Figure 4. A 5-point Likert scale (with 1 being the least feasibility and 5 being the most feasibility) was used to elicit respondents' opinions about the level of feasibility of prefabrication. The average score, which was weighted by the 5-point of Likert scale, represents respondents' general attitude to each question. The levels of feasibility in the main and branch pipe prefabrication of different piping systems and pipes in the pump room such as fire sprinkler system, water supply system, air conditioning water system, heating system, and drainage system were surveyed and the result is shown in Figure 4a. The feasibility of pipe prefabrication in pump rooms has a higher average score (average score of 4.25) than the prefabrication of fire sprinkler system (3.71), air conditioning water system (3.54), heating system (3.5), and water supply system (3.46). According to the collected case studies, the successful implementation of pipes in pump rooms has some difficulties. For example, if the equipment is not procured by contractors, the accurate sizes of connectors impede the developed of BIM. The verticality of pipes will have a significant effect on the operation performance of the piping system. The compensation method of deviation needs to be considered in advance. The successful implementation of prefabrication of pump rooms needs the integration of the distributor, manufacturer, and designer. The feasibility of pipe prefabrication in drainage systems is lower than others as the average score is only 2.5. This is because the pipes in a pump room are often installed by only one MEP contractor. There is no need to coordinate with other MEP contractors. The drainage system in a building is sloped. The slopes depend on the pipe diameter. For example, the recommended slope for pipes of diameter 50 mm is 25%. The small slope increases the risk of prefabrication. Figure 3: Overview of the respondents. (**a**) the respondents’ work year of experience; (**b**) the number of piping projects participated by respondents. Figure 4: Level of feasibility of piping prefabrication. (**a**) the level of feasibility of prefabrication in different types of piping systems; (**b**) the level of feasibility of prefabrication in different connection modes of piping; (**c**) the level of feasibility of prefabrication in different types of projects. The connection modes of the piping system are various, depending on the type of system, the line pressure, the pipe diameter, the connected valves or equipment, and the availability of material. According to the construction specification in China, the threaded coupling can be used in the pipe, of which the diameter is less than 80 mm. When the pipe diameter is larger than 100 mm and less than 150 mm, the groove coupling, welding, and flange coupling are applicable. The butt fusion jointing is used when the pipe is PPR. The welding and flange coupling are recommended when the pipe diameter is larger than 150 mm and the pressure in the piping system is big. In some circumstances, the connection mode depends on the available valves, for example, if the connector in the valve is a flange, the corresponding connection mode must be the flange coupling. As shown in Figure 4b, the welding and butt fusion jointing modes have a low average score for prefabrication feasibility. It seems that the piping system is not detachable using these two connection modes. When a length of pipe is welded with an elbow, they form a whole that is difficult to disassemble. By comparison with other connection modes (for example, groove coupling), groove coupling is not only detachable but also is easy to learn.