Building water supply and drainage under high-rise design?

The water supply and drainage engineering of high-rise buildings is quite different from that of ordinary multi-storey houses, such as the selection of pipes and the design of fire fighting system, which requires designers not only to understand the needs of users, but also to meet their specification requirements, pay attention to the use effect and improve design technology. The designed project should be economical, reduce the project investment, improve the project quality and satisfy all parties. The following consultation in Zhong Da will show you the water supply and drainage of buildings under high-rise design.

1 domestic water supply system

1. 1 water supply zoning model

The water supply mode used in high-rise buildings should conform to the water consumption characteristics of the buildings themselves. When reasonably selecting water supply zones, we should not only consider the users' own needs, but also select the most suitable water supply scheme in combination with the unified technical and economic analysis of other professions. Water supply is generally divided into three areas: high, medium and low. High-level water tank is suitable for high-level area (floors 19 ~ 32), and variable frequency speed regulation is used for water supply in middle area (floors 7 ~ 18). The low area (1 ~ 6 floors) is directly supplied with water by the municipal pipe network, using the municipal water supply pressure. In the case of saving investment, high and middle areas can also use constant-speed pump top water tank and variable-frequency water supply, and the energy-saving effect is also very remarkable.

1.2 Selection of water supply pipe

At present, there are many kinds of water supply pipes in the market, with different quality and great price difference. It brings difficulties to the selection of pipes in architectural engineering design. Commonly used water supply pipes are divided into metal pipes, non-metal pipes and composite pipes. (1) metal pipe: There are several kinds of metal pipes commonly used for indoor water supply: thin-walled stainless steel pipes, copper pipes and galvanized steel pipes. Its advantages are good toughness, durability, good impact resistance and convenient operation. Disadvantages: the price is high, so it is difficult to become a widely used water supply pipe, and it can only be used in some special occasions and places with high specifications. (2) Plastic pipes: there are many kinds and different characteristics. For example, the commonly used rigid polyvinyl chloride (UPVC) pipes have high impact resistance and chemical resistance, hard texture, corrosion resistance and no scaling, convenient installation and low price; However, the impact resistance is poor, and UPVC monomer and additives will ooze out during use, which is not suitable for hot water transportation, and the joint bonding process requires higher requirements and longer curing time. High-density polyethylene (HDPE) pipe is one of the best seismic resistance at present, with good toughness, fatigue strength, temperature resistance, impact strength, light weight and long service life. But welding requires electricity, mechanical connections and large connectors. The design should be selected according to the actual engineering situation. (3) Metal-plastic composite pipes: commonly used are plastic-coated steel pipes and aluminum-plastic composite pipes. Its advantages are high strength, convenient connection and aging resistance. , which is widely used in the market at present.

1.3 supercharging system selection

There are three schemes for water supply pressurization system: (1) The water supply at all levels adopts pool-pump-water tank combined water supply mode; (2) Water supply at all levels adopts the water supply mode of water pool (water tank)-frequency conversion water supply equipment-each water point; (3) Municipal pipe network-non-negative pressure water supply equipment-water point is used for primary water supply, and transfer water tank-variable frequency water supply equipment-water point is used for secondary water supply.

2 Drainage system

2. 1 domestic drainage system

The sewage flowing in the drainage riser is an extremely unstable gas-water two-phase flow, which is different from the general pressure flow and gravity flow. In high-rise buildings, due to the long drainage riser, large amount of water and large flow, the air pressure in the pipeline often fluctuates greatly, which may form a water plug, resulting in overflow of sanitary ware or damage of water seal. So that the odor in the sewer enters the room and pollutes the indoor environment. Both theory and practice show that the function of drainage system in high-rise buildings depends largely on whether the drainage pipeline ventilation system is reasonable or not. Therefore, ventilation system plays an important role in the drainage system of high-rise buildings. A perfect drainage system should meet the following requirements: (1) reasonable pipeline layout, good hydraulic conditions and rapid sewage discharge; (2) Keep the air pressure in the pipeline of the drainage system as stable as possible to prevent the formation of water plug and the destruction of water seal; (3) The pipeline shall be installed firmly to prevent vibration, vibration reduction and noise reduction; (4) Convenient maintenance.

2.2 Rainwater system

Building roof rainwater system can be designed according to different flow patterns: (1) Semi-confined roof rainwater drainage system: Type 65 and 87 system rainwater hoppers are mainly used, and the design flow pattern of pipe network is the transition flow pattern between free surface flow and pressure flow.

(2) The pressure flow roof rainwater drainage system, also known as siphon rainwater system, adopts siphon rainwater hopper, and the design flow pattern of the pipe network is pressure flow.

(3) Gravity flow roof rainwater drainage system: gravity flow rainwater bucket is adopted, and the design flow pattern of pipe network is pressureless, so the influence of water flow pressure is ignored in hydraulic calculation. According to Code for Design of Water Supply and Drainage in China (2009 edition) 4.9. 10, the design flow pattern of rainwater drainage pipes on the roof of high-rise buildings should be designed according to gravity flow. Because the current gravity flow rainwater hopper does not have the function of preventing overflow rainwater from entering the hopper, and the overflow port of the roof is generally more than ten centimeters higher than the roof, it is difficult to realize the idea that the overflow port excludes rainwater in the over-designed return period in engineering design. When rainwater enters the gravity flow system in the over-designed return period, the flow pattern in the system will change into semi-pressure flow or pressure flow, resulting in obvious positive pressure and negative pressure, which will cause the plastic pipe in the negative pressure area to be sucked down, the indoor inspection well to leak water, and even the pipeline system to be destroyed. Moreover, because the 65 and 87 rain buckets commonly used in the national standard drawing set will cause obvious pressure in the system, the rain buckets should be designed as a semi-pressure flow system. Therefore, the gravity drainage system of multi-storey buildings should use building drainage plastic pipes, while the gravity drainage system of high-rise buildings should use corrosion-resistant metal pipes and pressure-bearing plastic pipes. In addition, if the pressure flow drainage system is adopted, it is advisable to adopt pressure-bearing drainage cast iron pipes, pressure-bearing plastic pipes and steel-plastic composite pipes with smooth inner walls, and the working pressure of the pipes should be greater than the hydrostatic pressure generated by the clear height of the building. For plastic pipes used for pressure flow drainage, the external pressure against ring deformation should be greater than 0. 15MPa.

3 fire water supply system

3. 1 Selection of fire water supply system form

3. 1. 1 reduced pressure water supply mode

That is, a water tank and a set of fire pumps are set on the roof. The lift of water pump is generally about 100 ~ 170 milliohm. The high area is depressurized by a pressure reducing valve to supply water to the low area. This water supply mode has the advantages of small floor space, few water pump units, simple system, cost saving and construction and installation time. When there is a fire at the junction of high and low areas, just start a pump. However, it also has some disadvantages: it consumes a lot of electricity, but the fire pump does not need to run frequently, which is more economical. Another problem is that the water quality becomes higher after the water flows through the pressure reducing valve. Galvanized steel pipes are mostly used in fire water supply pipes, but they often rust due to long-term non-use, which easily blocks the filter in front of the pressure reducing valve and seriously affects the fire fighting effect. Therefore, it is very important to pay attention to the design of corrosion-resistant pipes, fittings and valves from this aspect. After that, it is necessary to strengthen daily management to ensure better water quality.

3. 1.2 parallel partition water supply mode

The high-level water tank and a group of fire pumps are set as high-level area and low-level area respectively. The water supply in the two areas is independent, and its water quality requirements are not as high as those of the pressure reducing valve, so the safety is better. The water pump is centrally arranged in the basement, which is convenient for management and consumes less power than the decompression water supply method. In order to increase the floor space of water tanks and pumps, a group of water pumps and partitioned water tanks are set up in the low area, but this way increases the cost compared with the reduced pressure water supply method. If there is a fire on any floor at the junction of high and low areas, two sets of water pumps should be started to increase the capacity of the power supply system. If you want to reduce a group of pumps, you need to use multi-stage double-outlet pumps.

3. 1.3 series district water supply mode

Water is supplied in series in different zones, and each zone is equipped with a water pump and a water tank. The water pump in each area pumps the water from the water tank to the water tank in the previous area, and the water tank in the tower-less water supply equipment supplies water to each floor. The water pump and water tank are arranged on the equipment floor. Advantages: the pump head and flow rate in each area are stable and designed according to actual needs, so the pump has high working efficiency and low energy consumption; The total demand of pipeline is small, saving investment. Disadvantages: the requirements of equipment layer (technical layer) are high; Each community has a water pump and a water tank; The pump is noisy. The water tank should be soup-proof, which is inconvenient for centralized management; The lower water tank has a large volume and a large structural load. High cost. The work is unreliable, and the water consumption in the upper area is limited by the lower area.

3.2 Anti-overpressure measures for fire water supply system

In high-rise buildings, automatic frequency conversion and speed regulation water supply equipment is widely used, which not only conforms to the fire water supply system, but also can change the flow at constant pressure. Generally, there are two measures as follows: 1) setting a backflow pressure relief device; There is a pressure relief valve on the branch pipe of the fire pool. When the pipe network pressure exceeds a certain range (30%) of the set working pressure, the pressure relief valve will automatically open to prevent the pipe network from overpressure. 2) When the system is partitioned, an adjustable pressure reducing valve can be used to reduce pressure; As long as the pressure behind the valve is set and stabilized by the adjustable pressure reducing valve, the working pressure behind the valve will not be affected by any changes before the valve. There will be no overpressure in the fire fighting pipe network after the adjustable pressure reducing valve.

3.3 Outdoor fire protection support indoor fire protection system

First of all, pay attention to the setting of outdoor fire hydrant and water pump adapter. Some civil high-rise buildings do not fully consider the connection between water pump adapter and outdoor fire hydrant. The connection between the outdoor hydrant and the water pump adapter can make the fire truck take water from the hydrant conveniently and quickly. The number of water pump adapters should be consistent with the number of outdoor fire hydrants, and the water pump adapters of indoor fire hydrants should be distributed. If there are more than two sets of pump adapters installed indoors, an appropriate number of fire hydrants should be added outdoors to meet the building fire protection requirements. Secondly, we should pay attention to the particularity of the fire hydrant in the front room of the fire elevator. Provide fire hydrants for firefighters. The main purpose of setting fire hydrants in the front room of the fire elevator is to open up passages. Can't count into the total number of fire hydrants.

To sum up, the water supply and drainage engineering of high-rise buildings is quite different from that of ordinary multi-storey houses, such as the selection of pipes and the design of fire protection systems, which requires designers not only to understand the needs of users, but also to meet their specification requirements, pay attention to the use effect and improve design technology. The designed project should be economical, reduce the project investment, improve the project quality and satisfy all parties.

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