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| Water Supply in High Rise Buildings |
Introduction:-
In General
- Designing skyscrapers is an extremely complicated art that integrates several different logistic operations and utilities.
- Plumbing is one of the more challenging problems to solve due to the loss of pressure as water travels up a vertical pipe.
- As the building gets taller, another problem arises as the water pressure at the bottom of a vertical pipe becomes too great for safe operation and building codes.
The Solution
- The early solution to this problem was a water tank mounted on the top of a building with fill pumps at the bottom of the building, a simple gravity down feed arrangement.
- Today, a system of pressure-reducing valves and sub-risers is used to manage the inconsistent water pressure throughout a skyscraper.
- Pressure-reducing valves reduce the pressure at the bottom of the building, while sub-risers increase the pressure for the skyscraper’s upper floors.
DISTRIBUTION SYSTEMS
DISTRIBUTION SYSTEMS IN HIGH-RISE STRUCTURES
– Direct Supply System
– Direct Pumping Systems
– Hydro-pneumatic Systems
– Overhead Tank Distribution (Down Feed Arrangement)
DIRECT SUPPLY SYSTEM
– Useful when pressure is available round the clock at the topmost floor.
– The pressure may not be available so generally floors above 2nd or 3rd storey face shortfall of water pressure.
DIRECT PUMPING SYSTEMS
- Water is pumped directly into the distribution system without the aid of any OHT except for flushing purposes.
- Pumps – controlled by pressure switch installed on the line.
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| Direct Pumping System Applicable Where There is Continuous Demand on System |
- Useful in buildings where a certain amount of constant use of water occurs.
- The system requires a constant and reliable supply of power.
- Power failure – the breakdown of the water supply system.
HYDRO-PNEUMATIC SYSTEM
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Variation of the direct pumping system.
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An airtight pressure vessel is installed on the line to regulate the operation of the pumps.
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| Hydro-Pneumatic System |
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The pressure switch installed in the pressure vessel/tank switches off after reaching the predetermined pressure when the operating pump is put to stop.
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An Air compressor is necessary to feed the water with air to maintain the air-water ratio.
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This system eliminates the need for an OHT and supplies water at a much higher pressure resulting in even distribution of water on all floors.
OVERHEAD TANK DISTRIBUTION (Down Feed Arrangement)
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| Overhead Tank Distribution |
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The system comprises water to one or more OHT placed at the topmost location of the hydraulic zone.
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Water distribution- through pipes generally located on the terrace through gravity (down feed)
WATER SUPPLY FOR MULTYSTORIED BUILDINGS
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| WATER SUPPLY FOR MULTYSTORIED BUILDINGS |
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In very tall buildings it is advantageous to use separate drinking and water ground, intermediate, and roof level cisterns. The separate drinking and cold water cisterns spread a load of water storage up the building and limit pressure in the distributing both to drinking outlets and sanitary appliances.
HOT WATER SUPPLY
HOT WATER SUPPLY
WATER STORAGE UNIT FOR HOT AND COLD WATER
HOT WATER SUPPLY
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Dividing the building into different zones
Drainage in High Rise Buildings
Drainage
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Drainage is another common issue in skyscrapers and is often just as difficult to solve as water pressure problems.
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When water falls vertically down a pipe, the water will adhere to the pipe’s walls until the pipe’s cross-sectional area is about one-fourth full.
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Once the gravity propelled water hits a horizontal bend in the pipe, the flow velocity drops dramatically and fills the pipe considerably more due to the lost speed.
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It is common practice to use relief or yoke vents to slow the water before it encounters a horizontal flow change.
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The piping at the base of a vertical drainage column must be secured, as to reduce the risk of breaking joints.
Venting
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Once the water is raised and used, it is discharged to a drainage system that includes a venting system- responsible for the flow of air in the drainage piping network.
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Air is critical to the drainage process because drainage flow is caused by sloping pipes, and the motive force is gravity.
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Absent air, the drainage would range from erratic to nonexistent.
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When the water in a pipe flows to a lower area, air must be added to replace the water, or a negative pressure zone will occur.
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If this zone is near a fixture, air will be drawn into the drainage system through the fixture trap with an easily identified gulping sound and very slow drain performance.
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This condition leads to poor performance throughout the drainage system and traps seal loss due to siphoning or blowout.
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It is however okay to place air vents in the fixtures themselves to increase water flow.
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As the number of fixtures increases, venting needs do as well, and a venting system evolves, with the branch, circuit, and loop vents at the appropriate locations.
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Aside from relieving pressure in the drainage system, the vent system allows air to circulate in both directions in response to the fluctuating flow in the drainage system.
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In many high-rise vent designs, where stacks need to offset horizontally on a given floor, a relief vent is required.
Drainage System
The following are the piping systems adopted in drainage of the high rise structures:
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Two-Pipe System
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One-Pipe System
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Single Stack System
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Single Stack System (Partially Ventilated)
TWO-PIPE SYSTEM
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Ideal when the location of toilets and stacks for the WC’s and waste fittings is not uniform or repetitive.
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In large buildings and houses with open ground and gardens, the sullage water from the waste system can be usefully utilized for gardening and agriculture.
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In high rises, the sullage is treated within the building for re-use as makeup water for cooling towers for air conditioning system and is used for flushing water-closets.
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Care should be taken that it has no connection with any water supply line, tank or system used for domestic and drinking supply.
ONE-PIPE SYSTEM
- Suitable where toilet layouts and shafts are repetitive. Requires less space, and is economical.
- The continuous flow of water from waste appliances in the pipe reduces the risk of blockage.
- The system eliminates the need for a gully trap which requires constant cleaning.
- Prevents pipe crossing problems and saves space
- It May not suitable if the flow is heavy.
SINGLE STACK SYSTEM (without vent pipe)
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Suitable where toilet layouts and shafts are repetitive and there is less space for pipes on the walls.
SINGLE STACK SYSTEM (partially ventilated)
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Is the same but the only modification is that it is partially ventilated.Also, you can connect the waste appliances such as washbasin, bathtub, sink or sink to a floor trap.
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