There are many problems with water, electricity, and gas – stemming from the pitfalls in water supply and drainage system design!

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This post was last edited by Hasty Passerby on 2018-9-13 at 16:27. Landmines in the design of water supply and drainage projects! I. Errors in the construction drawings specifications 1. The codes or standard drawings referenced in the construction drawings specifications are not the currently valid versions. The reason for the error was that, in order to save time, the designers copied the standardized specifications without making any changes. Over time, when the specifications or standard drawings were revised, these copies were not updated in a timely manner, resulting in the use of obsolete versions. 2. Some design specifications lack specificity, with little to no changes made to the standardization requirements. There are contradictions between the drawings and the specifications. As an important part of the design documents, the design specifications deserve sufficient attention, and any issues should be raised promptly during the review process. 3. The material and equipment list does not fully reflect the specifications; for materials with standard models, these standard models are not indicated, and instead only the manufacturer-specific models are listed. This issue should be brought up promptly during the review process, with a request that the designers make the necessary revisions. II. Insufficient detail in the construction drawings 1. In some projects, in an effort to speed up progress, detailed drawings (such as those for bathrooms, cable shafts, and other similar elements) are omitted. This often leads to disputes during construction, as the contractors may claim that the drawings are unclear and request change orders. 2. Generally, the design units responsible for pipeline integration drawings do not provide detailed cross-sections showing how the pipes are buried (as specific requirements are outlined in the construction codes and the drawing manual 04S520). This leads to disputes regarding the estimation of the work involved in digging, filling, and packing soil around the pipes. In the future, for matters that are not clearly specified in the \"Regulations on the Depth of Preparation of Architectural Design Documents,\" it would be advisable to include such details as part of the enterprise standards and specify them separately in the design briefs. 3. The water supply plan does not include diagrams of rainwater pipes; rainwater is only shown in the architectural drawings, while the rainwater pipe system is installed by the installation team. This poses significant difficulties for construction management and technical oversight. 4. The beam system diagram for the spray pipes is not shown. III. Design of kitchens and bathrooms 1. Layout of kitchens and bathrooms The layout of kitchens and bathrooms is generally handled by the architectural team. In units where the master bedroom has its own bathroom, the beams in the bedroom often lie beneath the bathroom floor slabs. If there is poor coordination between the architectural team and those responsible for plumbing, the DN100 sewage branches may end up located too low beneath these beams, thereby reducing the available headroom. In projects that require separate drainage systems for sewage and wastewater (such as in Shanghai), an improper layout of the sanitary fixtures can lead to the sewage and wastewater branches intersecting at the top of the bathroom on the lower floor, which in turn affects the headroom in that space. In the architectural field, when arranging sanitary fixtures such as washbasins, toilets, and bathtubs, the plumbing and drainage specialty simultaneously considers the appropriate locations and connections for the drainage risers and horizontal drainage pipes. There are also single-family or semi-detached multi-story villas, as well as themed residences. To take into account the layout of functions and the richness of space, architects often place the bathrooms above the living rooms, dining areas, or even bedrooms and kitchens; the drainage pipes run above the lower-level living rooms or rooms, which affects the quality of the villa (as shown in Figures 1 and 2 for certain single-family villas in a particular project). The layout of kitchens and bathrooms is a matter that involves multiple disciplines, so it is necessary to get involved early and coordinate proactively. From the perspective of professional design in water supply and drainage, the layout of kitchens and bathrooms in residential buildings takes into account two main aspects: ① It is essential to focus on a human-centered approach, ensuring that equipment selection and space arrangement meet the basic requirements of ergonomics; ② The location of the main water supply and drainage pipes should be appropriate, and the layout of the branch pipes should be simple, smooth, and logical. It is important to coordinate properly the relationship between the location of these pipes and the placement of sanitary fixtures. 2. For gas water heaters, in areas where they are widely used, special attention must be paid to ensuring that the positions of the openings for the inlet and outlet pipes of the gas water heater are appropriate with respect to those of the openings for the gas branches connecting to the gas meter. The gas water heater should be kept at a certain distance from the gas meter, so as to prevent the exhaust pipe of the gas water heater from being too close to the gas meter. Although, per regulations, the gas company is supposed to review the design drawings before construction, this aspect is often overlooked. Raising this issue only during the gas company’s final inspection will result in a lot of rework. Therefore, professional coordination between plumbing and drainage design and mechanical engineering design on minor issues cannot be ignored either. IV. Layout Design of Water Supply and Drainage Pipes 1. Coordination between rainwater drainage pipes and the exterior facade: In some projects, the color of the exterior walls is dark, creating a large contrast with the white color of the rainwater pipes, which leads to visual disharmony and affects the overall appearance. Solutions that can be used as references in the future: ① Coordinate with architectural professionals to locate rainwater downpipes and air-conditioning condensate pipes in recessed areas or hidden within the louvers of outdoor air-conditioning units; ② Customize rainwater downpipes to match the color of the exterior wall (the Wuyuan Bay No.1 project in Xiamen serves as a good example); ③ Avoid placing roof rainwater drainage pipes on balconies, as this can affect their usability; instead, use a balcony drainage pipe connected to the balcony’s floor drain to channel water into the sewage system; ④ Reduce the diameter of exposed air-conditioning condensate drainage pipes, for example, by changing from DN50 to DN40 or using DN25 water supply pipes. 2. Attention should be paid to coordinating the positions of the inlet pipe connection point for the washing machine, the drainage sink, and the socket for the washing machine: an inappropriate relative position between the washing machine and the drainage sink, or too large a distance between the washing machine and the drainage sink, or the socket for the washing machine not being on the same side as the water supply and drainage lines. This issue was present in one of the projects during the quality inspection at the end of last year; it should be resolved before the construction drawings are reviewed. 3. In some apartment layouts, the kitchen area is relatively small, and designers tend to overlook the requirement that plastic pipes should be kept at a distance of at least 0.4 meters from the edge of the stove, and at a distance of at least 0.2 meters from gas water heaters when arranging the plumbing pipes. Another issue that is often overlooked is that when holes are made in the exterior walls of kitchens and bathrooms, sometimes the exhaust vent of gas water heaters faces the plastic downspouts on the exterior wall, and the holes made for air conditioners also face these downspouts. As a result, residents have to drill new holes when installing air conditioners. 4. When arranging the drainage risers, if they are placed close to shear walls, in cases of shops with a large floor height at the bottom or high-rise residential buildings with basements, it is necessary to take into account the fact that the shear walls and the outer walls of the basements are usually thicker. The arrangement of the drainage risers should be coordinated with the structural team to avoid conflicts and to optimize the effective space utilization for the pipes. Similar situations are more common in some higher-rise residences. V. Installation of the fire hydrant system 1. In current development projects, low-to-mid height buildings are relatively common. To reduce the shared areas and address the issue of limited space in public areas, special attention should be paid to ensuring that the placement of fire hydrant boxes is aesthetically coordinated with the building design, while also minimizing any impact on residents; therefore, the plumbing and drainage specialists must get involved at an early stage. 2. Issues with outdoor pipes in fire protection systems: In projects where the indoor fire hydrant system has a centralized pump room, the design agencies often fail to give proper consideration to the material selection for the fire protection pipes that connect from the pump room to various buildings. They choose pipe materials based solely on the conditions for installation indoors; for the underground sections, galvanized steel pipes connected via grooves are used, ignoring the fact that some pipe materials or connection methods are not suitable for underground use. Shanghai Water Supply Company has local regulations requiring that fire pump rooms exceeding a certain size be located separately, and this is based on such considerations. VI. Other issues related to water supply and drainage design and installation 1. Noise problems in pump rooms. In high-rise residential buildings, the booster pump stations are usually located in the basement; due to space constraints, residential units are situated above these pump rooms. As a result, the noise generated by the pumps, especially the low-frequency vibrations, can propagate through the concrete structure and reach rooms located at greater distances (for example, in one project, the low-frequency vibrations from the underground pump room affected the residents in the third floor above). It is therefore necessary to use low-noise pumps. During construction, special attention must be paid to ensuring proper quality control of the vibration isolation measures for the pump foundations, and vibration prevention measures for pipes must not be overlooked. In addition, it is necessary to pay attention to selecting an appropriate design to keep the pressure entering the tank at no more than 0.15 MPa, or to use low-noise level control valves and other measures to achieve good noise reduction effects. 2. The issue of controlling water supply pressure: The maximum water pressure in residential water supply systems can be controlled by supplying water in stages with pressure reduction, so that the maximum pressure delivered by the system does not exceed the tolerance capacity of the water-using devices. However, when designing such systems, adherence to regulatory limits often results in higher water pressure for users in the lower floors of a building; this leads to easier damage to sanitary fixtures and water waste. At the inlet pipe connection for high-rise residential buildings, the water pressure should be kept at no more than 0.3 MPa. 3. Odor problems in bathrooms: In high-rise buildings (with more than 20 floors), residents living on the lowest floors report severe odor issues in their bathrooms after moving in. This floor level usually appears on the second floor, as the waste water from the bathrooms in the first floor is discharged separately outside. The second floor being at the lowest point of the vertical pipe, it is susceptible to local positive pressure in the drainage pipes, which can cause odors from these pipes to enter the interior. Special attention should be paid to installing S-shaped traps below the drains for floor drains, washbasins, and bathtubs on this floor; the depth of the water seal in such traps must be no less than 50 mm. When reviewing blueprints, it is important to ensure that the vertical pipe does not turn at the lowest floor level, as this could lead to fluctuations in drainage pressure. 4. The coordination issues related to landscape design, intelligence systems, and integrated utility networks are long-standing problems that attract a lot of attention; they are extremely complicated. A certain project has many lessons and experiences in this regard. In summary, several aspects need to be taken into consideration: ① Attention should be paid to the coordination among various design firms; ② Conflicts between the landscape design and pipelines must be avoided – the landscape design should be developed simultaneously, and after the preliminary draft of the integrated pipeline network is prepared, it should be overlaid on the landscape plan before further adjustments are made; intelligent systems should also be integrated into the landscape plan for the external pipelines; ③ Coordination between individual buildings and the overall layout is necessary; ④ Coordination between different groups of buildings is also important, as often different parties are responsible for each group, and municipal service providers submit requests in phases. Although there is an overall design plan, specific points of connection are sometimes overlooked in relation to the building layout, which leads to problems in subsequent construction phases. ⑤Special attention should be paid to verifying the alignment between the elevations of the water supply and drainage pipes and the vertical elevations shown in the building plans. VII. Several prominent issues after the commissioning of a certain project 1. Issues with the rainwater system: The gravity flow system for rainwater relies on internal drainage; all rainwater vertical pipes are connected to the basement’s rainwater horizontal main pipes, from which the water is discharged outside. During this year’s typhoon and heavy rain periods, severe pipe leakage due to disconnection at the expansion joints occurred on multiple occasions; when rainfall was light, leaks were observed at the expansion joints and cleaning ports. Problems in the construction include: ① Due to limitations imposed by the beam height and the elevation of external outlets, the slope of the horizontal stormwater pipes in the basement is insufficient; ② Expansion joints are installed at the junctions where vertical pipes connect to horizontal pipes, but no fixing supports are provided at the bends; ③ Rubber gaskets are missing at the cleanout openings; ④ Pipe supports have not been installed in sufficient numbers as required by the specifications. The design issue lies in the excessively low safety factor: too many rainwater pipes connect to the horizontal main pipes, with up to 11 roof-based rainwater pipes connecting to a single main pipe. Factors such as sudden increases in rainfall intensity and high flow rates are not taken into account; these can cause negative pressure within the rainwater system, as well as rapid changes in the pressure of compressed air bubbles, which in turn leads to shock vibrations in the pipes. This can result in leaks at the weakest points of the pipes. Although the design specifications do not explicitly state that UPVC pipes cannot be used for the horizontal main pipes in rainwater drainage systems, it should be taken into account that UPVC pipes have little pressure-bearing capacity at their joints, poor impact resistance, and a low safety factor. The flow conditions of rainwater within these pipes differ significantly from those in sewage drainage systems; therefore, flexible cast iron pipes should be given priority as a material choice, with flexible socket-connected UPVC plastic pipes for water supply being an alternative option. (In the Jinxiang Jiayuan project in Xiamen in 2003, the horizontal main pipes at the transfer layer were changed from the originally specified UPVC plastic pipes to UPVC plastic pipes for water supply, and no problems have occurred since then.) 2. Drainage issues in the parking lanes of underground garages: During the rainy season, rainwater from the surfaces outside the lanes overflows the first drainage ditch at the entrance and flows into the garage along the lanes, causing water to accumulate in the basement. Points that require special attention going forward are as follows: ① Install a first drainage ditch at the entrance and exit of the underground garage, and raise the ground surface in front of this ditch; ② Set up a second drainage ditch at the lowest point of the lane slopes, directing the water into nearby collection wells. It is also necessary to increase the capacity of these collection wells and equip them with pumps capable of handling high flow rates.

3. Water seepage through the ceiling of the basement: The soil layer covering the basement ceiling and the green areas there do not have proper drainage systems. Additionally, the exterior wall of the equipment room is located on the outer side of the basement’s elevation difference, allowing water from the soil layer outside to seep into the equipment room through the base of that wall. Since numerous pipes pass through the equipment room into the basement, these pipes become pathways for water leakage, resulting in significant leaks during the rainy season, and it is difficult to identify the source of the leaks. This issue can be summarized mainly in the following three aspects: ① Proper construction practices should be followed, with the height difference at the basement roof being located outside the exterior walls; ② The filled soil layer on the basement roof that is used for landscaping should be designed with proper drainage systems to prevent water accumulation; ③ Pipes passing into the basement must have their water-facing and backwater-facing sides sealed properly before they are concealed.