Master in Architecture. (Services in High Rise Buildings)

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1 Master in ()

2 1. Details of Module and its Structure Module Detail Subject Name Paper Name - Module Name/Title Water Supply to High Rise Buildings - 1 Objectives To explain the need and the capacity of the storage tanks in the building; To discuss the difference between the overhead tank and underground tank and storage capacity of each tank when they are adopted; and To discuss the different methods of water distribution to different houses in the building. Structure of Module / Syllabus of a module (Define Topic / Sub-topic of module ) This module presents the need for water storage in high-rise buildings, the quantity of water to be stored in the storage tank. The module also presents the different types of water distribution system to different houses in the building and the selection of the pump for pumping water.

3 2. 2. Development Team Role Name National Coordinator Subject Coordinator Paper Coordinator Content Writer/Author (CW) Content Reviewer (CR) Language Editor (LE) Dr. Monsingh D. Devadas Dr. Mohanlal Dr. Paneer Selvam Dr. S. Amal Raj

4 E-Text & Learn More 1.0 General Water supply is one of the important services to residential buildings because water is one of the causes for the transmission of diseases. Water-borne diseases, such as typhoid, cholera, dysentery, diarrhea and jaundice, are transmitted due to consumption of contaminated water. Part 9 (Plumbing services) of National Building Code (NBC) of India, contains the guidelines for the design of water supply and drainage systems in buildings. Today in a high-rise building, there are increasing challenges in providing safe water supply. A minimum of 70 to 100 litres per head per day (Lpcd) water supply is necessary to meet the domestic needs such as drinking, cooking, bathing and washing clothes, etc. In addition, 45 Lpcd water is required for flushing of toilet. In high-rise buildings, apart from these uses, water is also required for firefighting, which is in conformity with the requirements laid down in Part 4 Fire and Life Safety of NBC. 2.0 Storage of Water in Buildings In residential building storage of water is necessary for the following reasons: To provide against interruption of the supply by repairs to the mains, To tide over the intermittent supply from the source, and To maintain a storage level for firefighting purposes. The water may be stored in overhead tanks (OHT) and/or in underground tanks (UGT). 2.1 Capacity of a Storage tank Quantity of water to be stored depends upon the following factors: Hours of supply from the source, Rate and regularity of distribution to the consumers, and Consequences of exhausting storage Capacity of storage tank may be taken as: 33.3 to 50% of one day s requirement in case only OHT is provided; 50 to 150% in case only UGT is provided ; and 66.7% in the UGT and 33.3% in the OHT in case the storage is provided both in UGT and OHT.

5 2.2 Requirements of Storage tank The following are the important requirements of a storage tank: Adequate number of manholes in the tank for access and repairs is necessary. Manholes shall be provided with a locking arrangement to avoid misuse and tampering. Tanks greater than 900 mm deep shall be provided with corrosion-resistant catch rings or ladders to enable a person to reach the bottom of the tank. Each tank should be provided with an overflow pipe above the ground or terrace level to act as a warning pipe to indicate the overflow condition. Tanks with more than 5000 litres capacity should be provided with a vent pipe to prevent the development of vacuum condition, which might result in the collapse of the tank. Each tank should be provided with a scour pipe with an accessible valve for emptying the tank for cleaning and repairs. All overflow and vent pipes should be provided with a mosquito proof brass grating to prevent the entry of mosquitoes and insects. The top of the tank must be suitably sloped away from its centre for proper drainage of rain water. In case of the UGT, provision for draining of the tank is necessary. The UGT should not be located near any public or private sewer, septic tank, leach pit to prevent any contamination. In case of OHT, the bottom of the tanks shall be placed at a minimum of 2.0 m clear of the terrace slab to prevent leakage into the structural slab. 3.0 Water Distribution System in High-Rise Buildings The plumbing system for water distribution in the building shall be designed to supply equitable and adequate quantity of water with sufficient pressure at all floors of the building. There are four methods for the distribution of water to high-rise buildings: Direct supply from municipal mains Direct pumping system Hydro-pneumatic system Overhead tank s distribution 3.1 Direct Supply System This system is adopted when adequate pressure is available in the municipal mains laid in the street to feed water to the top-most floor in the building throughout the day.

6 3.2 Direct Pumping Water is pumped directly from the source well or UGT into the distribution system without the aid of OHTs except for flushing purposes. The pump is controlled by a pressure switch installed on the line. Normally, a jockey pump of smaller capacity is used to meet the demand during the low consumption and the main pump starts when the demand is greater. The start and stop operations of the pumps are accomplished by a set of pressure switches installed directly on the line. In some case, the timer switch is installed to restrict the operation cycle of the pump. Direct pumping system is suitable for buildings where a certain amount of constant use of water (such as for air conditioning) is always occurring. The system depends on the availability of constant and reliable power. The system eliminates the requirement of overhead tanks. 3.3 Hydro-Pneumatic Systems Hydro-pneumatic system is a variation of a direct pumping system. An air-tight vessel is installed on the pumping pipe line to regulate the operation of the pump. As the pump operates, the incoming water into the vessel compresses air at the top. When a predetermined pressure is built up in the vessel, a pressure switch switches off the pumps. As water is drawn in the system and pressure falls in the vessel, the pressure switch starts the pump at the preset pressure. An air compressor is necessary to feed air into the vessel and maintain the air water ratio. The system requires a reliable power supply to avoid disruption in the water supply. There is an alternate option for providing a variable speed drive pumping system, where a pump with a large variation in the pressure-discharge and speed of the pump is efficiently used to deliver water at the required rates by changing its speed with the assistance of an electronic device, which will reduce the rate of flow by varying the speed of the motor from 960 rpm to 3000 rpm. With this arrangement, the same pump is able to deliver water as required at different times of the day. The system consumes energy in proportion to the work done and saves considerable amount of power compared to the constant speed pumps. Hydro-pneumatic system generally eliminates the need for an overhead storage tank and may supply water at a much higher pressure in the upper floors than available from overhead tanks, resulting in equitable distribution of water to all the floors. 3.4 Overhead Tank Distribution This is the most common distribution system adopted by various types of buildings. The system requires pumping water to the overhead tanks placed at the top of buildings. Water collected in the overhead tank is distributed to the various parts of the building. Distribution is accomplished by providing down-take pipes to various fixtures. In order to maintain equitable distribution in all the floors, it is necessary to fix pressure-reducing valves in the branch pipes to the lower floors to have uniform pressures in all the branches. 3.5 Communication Pipes The communication pipe is the pipe connection between the street water main of municipal water supply and the stop cock in the supply pipe at the boundary of the premise. Connections up to 50 mm diameter may be made on the water main by means of screwed ferrules, provided the size of the connection does not exceed one-third size of the water main. In all other cases, the connection shall be made by a T-branch off the water main.

7 3.6 Pumps The functions of the pumps in water supply system are: To raise the water from a lower elevation to a higher elevation, as in the case of pumping water from a well or UGT to OHT. To convey the water through a pipe system from a source or treatment plant to a distant place for use. There are three types of pumps suitable for pumping water from wells. They are Centrifugal pumps, Submersible pumps, and Jet pumps. Selection of a pump depends on The duration of the availability of power The rate of discharge The difference in level between the lowest water level in the source water and the level at which the water is to be delivered.