into tanks. Once the bulb is full, the fluid will flow without further effort from the higher to the lower container. Many hand pumps will allow the passage of fluid through them in the direction of flow and diaphragm pumps are particularly good at this. Thus where the levels are correct large volumes of liquid such as swimming pools can be emptied with very little effort and no expensive energy use. Chain pump A chain pump is made of an endless chain carrying a series of discs that descend into the water, and then ascend inside a tube, carrying with them a large quantity of water. They are a simply made, old hand-powered pumping technology In the 18th century they were used as ship's bilge pumps. A chain pump is a type of water pump that uses a chain to move water from one place to another. It works on the principle of a continuous loop of chain moving through a series of sprockets, with attached buckets that lift water as the chain passes over the top sprocket and discharge it as the chain reaches the bottom. Direct action Direct action hand pumps have a pumping rod that is moved up and down, directly by the user, discharging water. Direct action handpumps are easy to install and maintain but are limited to the maximum column of water a person can physically lift of up to 15 m. Examples of direct action pumps include the canzee pump and the EMAS pump. Deep wells Deep well hand pumps are used for high lifts of more than 15 m. The weight of the column of water is too great to be lifted directly and some form of mechanical advantage system such as a lever or flywheel is used. High lift pumps need to be stronger and sturdier to cope with the extra stresses. The installation, maintenance and repair of deep well hand pumps is more complicated than with other hand pumps. A deep well hand pump theoretically has no limit to which it can extract water. In practice, the depth is limited by the physical power a human being can exert in lifting the column of water, which is around 30 m Diaphragm Diaphragm pumps have the advantage that they pump relatively lightly due to the lack of pulling rods and are corrosion resistant. Their disadvantage is that they need a specific length