Usually many people misunderstand water flow and water pressure. Most of the times the cause of inadequate water quantity (i.e. water flow) is attributed to pressure which is not correct.
It is the amount (quantity) of water that is available at the faucets. If water flow is high it will cause more wastage of water and if it is low it will cause inconvenience to the users.
It is the measure of force (or speed) at which water is available or passes through fixtures. If house water pressure is high it will also cause wear and tear of the fixtures and if it is low it will be inconvenient for the users as it will take more time.
To use water judiciously it is necessary to maintain sufficient house water pressure and water flow both at all appliances. All appliances don’t require same flow of water. For example: Bathtubs, flushes, dishwashers, showers require more flow of water than kitchen sinks, basins, etc. Sufficient water at respective outlet can be achieved by controlling water pressure and water flow rates i.e. by use of right size of pipes.
- In Direct Water Supply, System all the appliances will have pressure of the mains (the pressure at which water is released from municipality or private water companies).
- In Indirect Water Supply System, all appliances are not connected to water main hence it will have low water pressure or unequal water pressure at appliances faucets.
To regulate house water pressure in Water Supply System, pressure limiting or pressure reducing valves or controls are installed. To increase pressure in Indirect Water Supply system, storage water tank should be placed at some height so that water will flow down due to gravity. Pressure can also be increased by introducing booster pump in line.
Flow rate of water can be regulated only by selecting the correct pipe size. Regulating flow will maintain a constant flow, independent of water pressure.
Acceptable flow rates and water pressure for fixtures and appliances are as follows:
|Liters/sec||Liters/min||Gallons/min||Kilogram/ cm²||Head (in Meter)||Pound Force per sq inch|
|Basin||0.1 l/s||6 l/m||2 gpm||0.56 kg/cm²||5.6 m||8 psi|
|Bath||0.3 l/s||18 l/m||5 gpm||0.56 kg/cm²||5.6 m||8 psi|
|Sink||0.2 l/s||12 l/m||3 gpm||0.56 kg/cm²||5.6 m||8 psi|
|Shower||0.1 l/s||6 l/m||2 gpm||0.56 kg/cm²||5.6 m||8 psi|
|Laundry Tub||0.2 l/s||12 l/m||3 gpm||0.56 kg/cm²||5.6 m||8 psi|
|Dishwasher and Washing Machine||0.2 l/s||12 l/m||3 gpm||0.56 kg/cm²||5.6 m||8 psi|
|WC, Tank||0.1 l/s||6 l/m||1.6 gpm||1.05 kg/cm²||10.5 m||15 psi|
|WC, Valve||1.2 l/s||72 l/m||25 gpm||1.05 kg/cm²||10.5 m||15 psi|
Pressure can neither be increased by decreasing pipe size nor quantity of flow can be increased merely by increasing pressure. Thus the pipe leading to dishwasher or bathtub needs to be larger than the one for basin. Pressure can be increased by placing the tank at height or by installing booster pumps.
Therefore, it is advisable to hire the plumbing consultant to design the network, who will choose the right diameter of the pipes, which will not only reduce frictional losses but will deliver the required quantity at desired speed i.e. pressure.