[[Image:deep-well piston handpump No. 6 icon.png|right|100px]][[Image:PistonPump.jpg|thumb|right|300px200px|Afridev pump: a deep-well piston handpump. <br> Photo: S.K. Industries.]]
With a deep-well piston handpump, the piston is placed in a cylinder below the water level, which is usually 15–45 m below the ground. The pumping motion by the user at the pump stand is transferred to the piston by a series of connected pumping rods inside the rising main. On the up-stroke, the plunger lifts water into the rising main, and replacement water is drawn into the cylinder through a foot valve. On the down-stroke, the foot valve closes, and water passes the plunger and is lifted on the next up-stroke. The pumping height is limited only by the effort needed to lift the water to the surface. Nowadays,
most pump cylinders have an open top. This allows the piston and foot valve to be removed through the rising main for servicing and repairs, while the rising main and cylinder stay in place. The pump rods have special connectors that allow them to be assembled or dismantled without tools, or with only very simple ones. The connecting joints incorporate pump rod centralizers that prevent wear of the rising main. To a large extent, improved models can be maintained at village level.
===Suitable conditions===
'''Range of depth:''' 15–45 m, although depths of up to 100 m are possible.<br>
'''Area of use:''' Rural and low-income periurban areas where groundwater tables are within 100 m (but preferably within 45 m) from the surface.
===Construction, operations and maintenance===
The pump is operated by moving the handle up and down, or by rotating the handle of a flywheel. This can be done by adults and even children, since handle forces are usually kept within acceptable limits (depending on the brand and lifting heights). Preventive maintenance usually consists of checking that the pump is functioning, and cleaning the pump and pump site daily. Each week, the pump should be greased, and once a month all parts of the pumpstand must be checked. Small repairs include replacing bearings, cupseals and washers, and straightening bent pumping rods, etc.
— corrosion is a problem, especially where the groundwater is aggressive, and it can affect the pump rods if they are not made of stainless steel, the rising main (if not galvanized iron tubing), the cylinder, the housing for the pumphead bearing, and other pumpstand parts;<br>
— handles become shaky or broken, mainly because of worn-out bearings;<br>
— the number of problems usually increases with increasing depth of the groundwater (the maximum lift for a pump varies according to the brand, but is usually 45–100 m).<br>— with some pump brands, or when the water must be lifted from a great depth, the pump handle may require considerable strength to turn it;<br>— to reduce the number of major repairs, the rising main should be made of the highest-quality material available;<br>— rigorous quality control is needed for deep-well piston handpumps, since many are produced in developing countries;<br>— deep-well piston handpumps may require considerable torque to start them, and the pump may be driven by a windmill; as a result, rotary pumps are often preferred because of their lower starting torque. ===Costs===In 1985, for a well 25–35 m deep, prices ranged from about US$ 40 for a cylinder, plunger and foot valve set (installed under a locally-made pumphead), to over US$ 2300 for a complete pump with stainless steel parts. Most good pumps cost US$ 300–500. ===Acknowledgements===* Brikke, François, and Bredero, Maarten. ''[http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CC0QFjAB&url=http%3A%2F%2Fwww.who.int%2Fwater_sanitation_health%2Fhygiene%2Fom%2Flinkingintro.pdf&ei=cwJpT-zaO-OiiQKCst2rBw&usg=AFQjCNEWOQhTgF3a7lzhuw5OA2KmbVGxcA&sig2=Rt2EURUyGVqDcwFg6p0xAw Linking technology choice with operation and maintenance in the context of community water supply and sanitation: A reference document for planners and project staff]''. World Health Organization and IRC Water and Sanitation Centre. Geneva, Switzerland 2003.
