If you live in a town or city, you probably don't give much thought to how the water you use each day gets to your house. Even small villages often provide a network of supply pipes that transport water to each home in the neighborhood. All you need to know is how to open the tap at the sink.
Your source for well water pumps and pre-pressurized water storage tanks plus. Pump and control systems for irrigation, stockwater, wash systems, cooling.
Move a few miles out of town and the picture can change. While the inner workings are still—thankfully—invisible, your water supply is independent from the neighbor's down the road. Each home has its own well from which to draw water. More than that, each home has its own electromechanical system for getting the water from the well to the house. At the heart of each system is a pump, and the most common types are jet pumps and submersible pumps.
Well types
In many areas of the country, finding potable water is as easy as getting out a shovel and digging a hole in the ground. Okay, maybe 'easy' isn't the right word, but wherever the water table is only several feet below the surface of the ground, part of the battle may already be over. In such a shallow-well situation, lifting the water up to the house is going to be a little easier, if only because the distance you have to move it is modest.
If your area doesn't have a high water table, or if it lacks a stable supply of potable water near the surface, you must dig deeper to achieve the same result. And because a deep well means that the water has to be lifted farther, the strategies for moving it change.
Shallow-well pumps
These days, the most common pump for a shallow well is a jet pump. Jet pumps are mounted above the well, either in the home or in a well house, and draw the water up from the well through suction (see Single-Drop Jet-Pump System diagram on next page). Because suction is involved, atmospheric pressure is what's really doing the work. Think of the system as a long straw. As you suck on the straw, you create a vacuum in the straw above the water. Once the vacuum is there, the weight of the air, or atmospheric pressure, pushes the water up the straw. Consequently, the height that you can lift the water with a shallow-well jet pump relates to the weight of the air. While air pressure varies with elevation, it's common to limit the depth of a jet-pump-operated shallow well to about 25 ft.
Jet pumps create suction in a rather novel way. The pump is powered by an electric motor that drives an impeller, or centrifugal pump. The impeller moves water, called drive water, from the well through a narrow orifice, or jet, mounted in the housing in front of the impeller. This constriction at the jet causes the speed of the moving water to increase, much like the nozzle on a garden hose. As the water leaves the jet, a partial vacuum is created that sucks additional water from the well. Directly behind the jet is a Venturi tube that increases in diameter. Its function is to slow down the water and increase the pressure. The pumped water–new water that's drawn from the well by the suction at the jet–then combines with the drive water to discharge into the plumbing system at high pressure.
Because shallow-well jet pumps use water to draw water, they generally need to be primed–filled with water–before they'll work. To keep water in the pump and plumbing system from flowing back down into the well, a 1-way check valve is installed in the feed line to the pump.
Breaking the depth barrier
Unfortunately, you may have to go a little deeper than 25 ft. for your water. Surprisingly, you can still do it with a jet pump. It simply involves separating the jet from the motor and impeller housing and placing the jet assembly down in the water (see Double-Drop Jet-Pump System diagram). In a typical deep-well jet-pump configuration, one pipe mounted to the impeller housing drives water down into the jet body that's located about 10 to 20 ft. below the minimum well water level. A second pipe connects the output side of the jet body back to the pump.
At the jet, the increase in water velocity creates the partial vacuum that draws standing well water into the second pipe and then back into the pump and plumbing system. Deep-well jet pumps use both the suction at the jet to bring water into the system and pressure applied by the impeller to lift the water.
To prevent overpumping the well, a deep-well jet-pump installation may include a 35-ft.-long tailpipe. It's connected to the intake end of the jet housing and extends down into the well. If the water level dips below the level of the jet housing, the pump operates in the same manner that a shallow-well pump does. While flow rate drops off, water will be available until the level drops below about 25 ft. from the jet housing-the limit for a shallow pump. The 35-ft.-long tailpipe effectively ensures that the well will never be pumped out. Of course, the height of the jet over the water level affects performance. The farther away it is, the less efficient the pumping becomes.
Like shallow-well systems, a jet pump in a deep-well system needs to be primed to operate. A foot valve at the bottom of the well piping prevents water from draining from the pipes and pump. Jet pumps that have two or more impellers are called multistage pumps.
Moving to the source
While a jet pump can reliably handle a well several hundred feet deep, a more effective solution is to move the pump down into the well so, instead of lifting the water, it's pushing it up. A typical submersible pump is characterized by a long cylindrical shape that fits inside the well casing. The bottom half is made up of a sealed pump motor that is connected to the aboveground power source and controlled by wires. The actual pump half of the unit is comprised of a stacked series of impellers-each separated by a diffuser-that drives the water up the pipe to the plumbing system.
In modern installations, the well casing outside the home is connected to the plumbing system by a pipe that runs beneath the ground to the basement (see Submersible Pump System diagram). This horizontal pipe joins the well pipe at a connector called a pitless adapter. The function of the adapter is to permit access to the pump and well piping through the top of the well casing, while routing water from the pump into the plumbing system.
While submersible pumps are more efficient than jet pumps in delivering more water for the same size motor, pump or motor problems will necessitate pulling the unit from the well casing-a job that's best left to a pro. However, submersibles are known for their reliability and often perform their role 20 to 25 years without servicing. Submersible pumps may also be used in shallow wells. However, silt, sand, algae and other contaminants can shorten the pump's life.
Common elements
No matter what kind of system you have, the components on the output side of all pumps are similar.
Pumps are not intended to run continuously, and they don't start each time you open a tap or flush the toilet. In order to provide consistent water pressure at the fixtures, the pump first moves water to a storage tank. Inside a modern tank is an air bladder that becomes compressed as the water is pumped in. The pressure in the tank is what moves the water through the household plumbing system.
When the pressure reaches a preset level, which can be anywhere from 40 to 60 psi, a switch stops the pump. As water is used in the home, pressure begins to decrease until, after a drop of about 20 psi, the switch turns on the pump and the cycle is repeated. You'll find the pressure gauge mounted on the tank with wires leading to the switch that controls the pump.
Shravanabelagola lake in Karnataka
An irrigation tank or tank is an artificial reservoir of any size. They are mainly found in India.[1] It can also have a natural or man-made spring included as part of a structure. Tanks are part of an ancient tradition of harvesting and preserving the local rainfall and water from streams and rivers for later use, primarily for agriculture and drinking water, but also for sacred bathing and ritual. Often a tank was constructed across a slope so to collect and store water by taking advantage of local mounds and depressions.[2] Tank use is especially critical in parts of South India without perennial rainfall where water supply replenishment is dependent on a cycle of dry seasons alternating with monsoon seasons.
Tank design[edit]
Water is considered a purifying and regenerative element in India, and is an essential element of prayer and ritual. Water is also revered because of its scarcity in western India where dry and monsoon seasons alternate and failure of the monsoon season means famine and death while plentiful water replacing irrigations sources is a time of rejoicing. This resulted in building water storage tanks that combined the practical and sacred.[3]Since ancient times, the design of water storage has been important in Indian architecture. As early as 3000 BC, sophisticated systems of drains, wells and tanks were built to conserve and utilise water. Tank building as an art form began with the Hindus and developed under Muslim rule.[4]
An example of the art of tank design is the large, geometically spectacular Stepped Tank at the Royal Center at the ruins of Vijayanagara, the capital of the Vijayanagara Empire, surrounding the modern town of Hampi. It is lined with green diorite and has no drain. The tank was filled by aqueduct.[5]
Village tanks[edit]
A tank in Tamil Nadu
Ralegaon Siddhi is an example of a village that revitalised its ancient tank system.In 1975 the village was drought-stricken. The village tank could not hold water as the earthen embankment dam wall leaked. Work began with the percolation tank construction by the villagers who donated their labor to repair the embankment. Once this was fixed, the village's seven wells below the tank filled with water in the summer for the first time in memory. Now the village has a supply of water throughout the year.[6]
Temple tanks[edit]
Tanks known as 'Pushkarni' or 'Kalyani' also known as 'Kund' in Hindi are reservoirs with steps leading down to the water, generally found in South India, and sometimes constructed within the walls of a temple complex.[7]
Bathing in the sacred waters of a temple tank was believed to cure worshippers of afflictions such as leprosy and blindness.[8] Many temple tanks are decaying and drying up today.[9]
Stepwells[edit]
Stepwells, also called bavdi (Hindi: बावड़ी) or bavli (Hindi: बावली), are wells in which the water can be reached by descending a set of steps. They are most common in the west of India.
Stepwells were often used for leisure, providing relief from daytime heat. This led to the building of some significant ornamental and architectural features, often associated with dwellings and in urban areas. It also ensured their survival as monuments.
Modern tank management[edit]
The development of large-scale water management methods and hydroelectric generation have replaced much of the local efforts and community management of water. For example, the state of Karnataka has about 44,000 artificial wetlands locally constructed over many centuries. At least 328 are threatened today.[10]
However, recently a tank regeneration movement initiated by communities and non-governmental organisations (NGO) has arisen.[2] Today, there are approximately 120,000 small-scale tanks, irrigating about 41,200 km² in semi-arid areas of India.[11] This constitutes about one third of the total irrigated land in South India.[12]
Gallery[edit]
- A shrine in a ruined tank at Vijayanagara in Karnataka
- A stepped temple tank at Belur in Karnataka
- Pothundi Reservoir in Kerala
- A tank at Badami in Karnataka
- A bavdi at Shekhawati in Rajasthan
- A johad at Thathawata in Rajasthan
- A well at Trikuteshwara temple in Karnataka
- A temple pond and waterfall at Ellora Caves in Maharashtra
- Adalaj Stepwell in Gujarat
- A tank used for irrigating a market garden on Lamma Island in Hong Kong
See also[edit]
- Noyyal River - Tanks System
- bavdi or stepwell
Notes[edit]
- ^'Architecture on the Indian Subcontinent - glossary'. Retrieved 2006-12-18.
- ^ ab'Tank management'. rainwaterharvesting.org. Retrieved 2006-10-17.
- ^Thapar, Binda (2004). Introduction to Indian Architecture. Singapore: Periplus Editions. p. 24. ISBN978-0-7946-0011-2.
- ^'Architecture - Stepwells'. Retrieved 2007-01-09.
- ^'Great Tank'. art-and-archaeology. Retrieved 2007-01-13.
- ^'Ralegan Siddhi : A village Transformed'. Retrieved 2006-10-30.
- ^'Architecture of the Indian Subcontinent - glossary'. Indian Architecture. Retrieved 2006-10-17.
- ^'Sun Temples in India'. TempleNet. Retrieved 2006-10-17.
- ^'Ponds, tanks relics of a bygone era'. AmritsarPlus Online Edition. Retrieved 2006-10-17.
- ^'Bird monitoring at Rampura and Kalkere tanks'. aroche.org. Retrieved 2006-10-17.
- ^Anbumozhi, V.; Matsumoto, K.; Yamaji, E. (2001). 'Towards Improved Performance of Irrigation Tanks in Semi-Arid Regions of India: Modernization Opportunities and Challenges'. Irrigation and Drainage Systems. 15 (4): 293–309. doi:10.1023/A:1014420822465. INIST:13552012.
- ^Arumugam, N.; Mohan, S.; Ramaprasad, R. (1997). 'Sustainable Development and Management of Tank Irrigation Systems in South India'. Water International. 22 (2): 90–7. doi:10.1080/02508069708686676. INIST:2829920.
References[edit]
Palanisami, K, and Easer, E.W. (2000). Tank Irrigation in the 21st Century—What Next? Discovery, Delhi, Discovery. ISBN81-7141-558-X.
External links[edit]
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