To access water that is underground, farmers can use wells. Here, a different kind of pump is needed to move the water upwards. A manual pump works like a syringe in a medicine bottle: when the piston is pulled up, water is sucked up. This is because the piston�s upward movement creates an empty space with a little air pressure, so the water I pulled up to fill the gap. Then a little air pressure, so the water is pulled up to fill the gap. Then a little door, called a valve, is pushed open when the piston is pushed back down. The water flows through it and is pushed out.
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