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The right tool

A compact guide to choosing the right kind of water pump for home use

Water pumps have proven to be an integral part of our residential setups over the years. Thanks to these powerful and efficient devices, moving water from ground levels to top floors of high-rise buildings, that too without any major manual interference, has become possible. The use of water pumps to extract water from underground sources and transferring it to overhead tanks is increasing in rural and urban areas. Buying an efficient water pump can not only help you gain greater efficiency and performance but also save energy and reduce costs.

However, if you are in one of the metro cities of the country, it is likely that one of the members of your family has cribbed, some time or the other, about having to switch on and switch off the water pump to either fill the groundwater tank or lift water to the tank on the roof. And worse than anything else is when there is no water in the house because either the pump could not lift it with enough pressure or crashed while performing its duty.

Now, In spite of widespread usage, you might be confused which one to invest in as there are many options available in the market. So here's a simple guide to how BIS Standards can help you make a wise choice for energy-saving and cost-cutting with providing greater efficiency and reliable performance.

You must have come across "ISI" mark while searching the options in market. The ISI mark certifies that a product conforms to an Indian standard (IS) developed by the Bureau of Indian Standards (BIS), the National Standards Body working under the administrative control of Ministry of Consumer Affairs, Food & Public Distribution, Govt. of India.

The erstwhile Indian Standards Institution (now Bureau of Indian Standards) was established in the year 1947 with the objective of harmonious development of standardisation activity in India. Formulation of Indian Standards is one of the core activities of BIS.

Indian Standards are formulated through specialist technical committees to deal with specific group of subjects. The committee structure is designed in such manner as to bring together all those with a substantial interest in a particular field, so that standards are developed keeping in view the balance of interests among the relevant stakeholders like manufacturers, users, technologists and regulators. This is done after taking into account all significant viewpoints through a process of wide consultation. As a policy, the standards formulation activity of BIS has been harmonised as far as possible with the relevant standards laid down by the International Organisation for Standardisation (ISO)/International Electrotechnical Commission (IEC).

Indian Standard IS 8472 specifies the technical requirements for regenerative, that is, repeated centrifugal action pumps for handling clear, cold water suitable for domestic water supply.

The main factors in deciding the right pump are as following-

Materials of Construction: It is recognised that a number of materials of construction for mounting purposes, thermal protection, earthing requirements, type of enclosure and method of cooling are available to meet the needs for pumps handling clear, cold water. Provision of handling typical materials are indicated in IS 8472 for the guidance of the manufacturers and the users.

Maximum Head Lift: It is the total height from the source of the water to the destination or drainage point. This provides the power to move water over a distance.

Discharge: The discharge of a pump is the usable volume of liquid distributed by the pump in the time unit. It is usually denoted with the letter Q and is measured in the unit meter cube per second (m3/s).

Power: The power imparted into a fluid increases the energy of the fluid per unit volume. Thus, power depends on the conversion of the mechanical energy of the pump mechanism and fluid elements present inside the pump.

Efficiency: The pump set runs for years and remains in use almost every day. For a pump that is of the capacity of half or one kilowatt, power consumption can be substantial. The efficiency of a pump is the ratio between the power supplied to the fluid and the power absorbed by the pump, that is, the mechanical power transferred by the electric motor. Higher efficiency is considered better in terms of higher water output with low power consumption.

Duty Point: The duty point is the intersection between the pump performance curve (between flow and generated head) and the system's characteristics (pressure loss in the system as a function of the flow).

IS 8472 prescribes the following specifications and testing parameters to evaluate the factors affecting Pump's performance-

Hydrostatic test: This determines whether the pump casing is made of robust construction to withstand the shut-off pressure for a specified time at the guaranteed duty point.

Self-Priming test: This test is to be carried out to note the total elapsed time between starting the unit and the time required to obtain a continuous flow through the discharge pipe against the declared time by the manufacturer

Temperature-rise test: The test shall be conducted for maximum current in the operating head range with rated voltage and supply frequency. Lower temperature rise is good for better performance of the pump.

Guarantee of Performance: The pumps shall also be guaranteed by the manufacturer against defects in material and workmanship and for their performance of discharge, total head and input power at the guaranteed duty point. IS 8472 also prescribes the verification procedure for the actual pump performance curve to determine whether the guaranteed duty point condition in respect of declared head, discharge and power input have been met or not.

Hence, as an aware consumer you must ascertain that the manufacturer has clearly indicated all the relevant parameters e.g. rated speed, total head, discharge and power input at the guaranteed duty point, operational head range, motor rating etc., and the pump meets the requirements specified in IS 8472. Don't forget to look for ISI mark next time you plan to buy a pump so that you never get cribbed at about your pump again.

Ravindra Beniwal is presently working as "Scientist-B" in Bureau of Indian Standards, Govt. of India. Views expressed are strictly personal

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