Difference between Hydropneumatic and Gravity system of water supply?

Answer 1

I.GRAVITY TANK SYSTEMSL.NoADVANTAGESDISADVANTAGES1Extremely simple - there is no complicated or sophisticated controls.Tank must be elevated. Provisions must be made to support the water filled tank adequately. A tank on the roof is unsightly, and if it is enclosed and dressed up there is additional architectural expense.2Most reliable - It is the only system which has a reserve capacity in the event of a power or water supply failure.The weight of the water filled tank can increase structural costs.3Economical - Operating costs are much less, and capital expenditure is generally no higher than for other systems.Tanks required periodic cleaning and painting.4Minimum maintenance - The only requirement beyond those required for all systems is periodic cleaning and possible repairing of the tank.If a tank ruptures, large quantities are released which could cause extensive damage.5Uses less energy - Pump head and , therefore , horsepower is less than in other systems. The pumps operate only to replinish the tank, and then stop so that a high horse power pump is not required to satisfy low demands as is required in the booster Pump system. The pumps operate at the optimum point on the pump curve for greater efficiency and less energy wastage.Terrace floor is full of piping network and ring mains which is a draw back,then these terraces are not treated as common terrace area.6The pumps in a gravity system always operate at full capacity and peak efficiency, and shut down when there is no demand.Requires bulky overhead tanks7System pressure is less than 2Kg/sqcm and hence failure of CP fittings is remote.Equal pressure can not be achived at all the draw-off points.8Back-up power not necessary.9The fixtures at floor level immediately below over head tank will not have sufficient residual pressure for efficient operation / working of fixtures unless the staging of overhead tank is increased.10Not suitable for sloped roof terracesII.HYDROPNEUMATIC SYSTEMSL.NoADVANTAGESDISADVANTAGES1Less floor space is required as there are no large tanks to take up valuable space, and verticle pumps occupy considerably less area than horizontal pumps.Sophisticated controls - Manufacturer's trained personnel are usually required for adjustments and other routine maintenance2The intial cost can always be off setted with construction of OHT & its impact on structural members. Each system installation must be evaluated seperately.There is no emergency water reserve. Power supply must be 24/7, The building is without water if power failure occurs / with DG backup, the water supply is disrupted or the pumps fail to operate for any reason.3Uniform pressure can be achieved at all fixture outlets irrespective of the locationNoise problems - If other than multi-stage turbine pumps are used, there is a very serious problem. If centrifugal pumps are used, the danger of low-flow turbulence and high flow cavitation requires special attention.Over sized pumps aggravate the condition.4Eliminates Piping distribution networks at terrace Level. The piping cost is less compared to gravity system because of telescoping design.At least one pump must operate continuously, even for extremely small demands.5Best available option for sloped roof terracesThe pumps must operate over a wide range of capacities. The maximum operating efficiency of the pumps is lost. Operating costs is higher. At least one pump is always running. The horse power of the pumps is always greater than is required for the gravity tank system. The pumps do not always operate at the optimum point on their curves to achieve max effeciency.