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About Water Pumps
It doesn't always have to be the same as the flooded cellar. It can also be "only" the full rain barrel or cistern that needs to be emptied out for cleaning. Or you plan to use the water for watering. However, in the house and in the garden, tasks often occur, which can be done with a suitable pump in no time at all.
In order to determine which pump is best suited for your application, it is recommended to look more closely at the pump types:
Terms from pump technology
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Suction height
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Flow rate
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Delivery lift
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Immersion depth
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Friction losses
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Switched-on time
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solids size:
Pump accessories
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Pump filter
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Electronic pressure switches
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Dry-running protection
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Float Switches
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Suction hose
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Dimensions
Terms from pump technology
If the required pump type is determined, however, questions regarding the performance characteristics and technical data are repeatedly raised. For this reason, we have summarized the most common technical expressions of pump technology and provided a brief explanation.
Suction height
The suction height is the difference in height between the water surface and the higher pump. Regardless of the pump output, the suction height that can be reached in practice is approx. 7 - 8 m. If larger suction heights are to be overcome, the water must be transported to the higher-standing suction pump with a pressure pump.
Although some pumps are called self-priming, garden or centrifugal pumps should always be filled with water before operation to avoid damage from dry running.
Important:
The suction hose must first have the required cross-section, which depends on the pump performance and can be read in the technical data sheets. In addition, it must be designed in such a way that it cannot be compressed due to the prevailing vacuum within the suction hose.
The flow rate
Flow rate refers to the maximum amount of water that can be pumped into a given period of time. The data is given either in liters per minute (l/min) or liters per hour (l/h).
Note
The flow Q (l/h) depends on the delivery height H (m). The higher the delivery height, the lower the delivery rate and vice versa. The quality of a pump can be assessed using the pump characteristic in the technical documentation. With the help of the characteristic curves one can read exactly how much water is still pumped at a certain delivery height.
The power diagram on the right shows the ratio of the delivery height and flow rate for a pump with a max. delivery height of 55 m and a max. delivery rate of 5000 l/h. The characteristic curve shows exactly how large the expected flow rate is at a certain delivery height.
The delivery height
Delivery height indicates the maximum difference in height between the water surface, or the pump when it is outside the delivery medium and the highest point at which the pump can deliver the water. The delivery height is dependant on the pressure that the pump can generate. A pressure of 1 bar corresponds to a water column of approx. 10 m. For a pump capable of producing a pressure of 2.5 bar, the delivery height corresponds to approx. 25 m (see also pump curve).
Immersion depth
The immersion depth is only specified for submersible pumps and refers to the maximum water depth in which the housing seal can withstand the prevailing water pressure.
Friction losses
The actual performance of pumps is affected by various external factors. Irregularities in the line, such as Bends, angles, elbows and connections cause loss of power. Friction losses in cables are also one of the most important factors. In each water pipe friction occurs at the inner walls of hoses or pipes. To minimize these frictional losses, always use a hose with the largest possible diameter.
The friction losses are specified as pressure losses in meters of water column (MWS) and depend on the clear width of the hose (LW) as well as on the flow rate to be supplied (l/min).
The friction losses can be calculated exactly using the table on the side. For a 1 inch diameter 5 m hose with a flow rate of 50 liters per minute, the pressure loss due to friction is 0.4 MWS.
Switched-on time
Not every pump is designed for continuous or long-term operation. Depending on the model and construction, some low-voltage pumps require appropriate cooling pauses. Refer to the technical data sheets for the length of time a pump may be operated at one time. If the duty cycle (ED) is specified in percent, 100% refers to one hour. A pump with an ED of 50% may therefore run continuously for a maximum of 30 minutes.
In this context, the power supply must also be taken into account. If a 12 V pump is operated on a power supply unit that provides a significantly higher output voltage (e.g. 13.8 V), the switch-on time is reduced because the power consumption is higher. However, the operating conditions of the pump (hose diameter, delivery height, ambient temperature, etc.) also play a major role in the maximum useful duty cycle. If in doubt, check the operating temperature of the pump.
solids size:
Solid size refers to the maximum dimension of solid particles that a pump can carry. This is usually given in millimeters. If larger particles are present in the water, the pump may be blocked or damaged.
Pump accessories
The operational capability, efficiency and longevity of a pump depends to a large extent on the operating conditions. With effective and practical accessories, you can make the operation of your pump safer and more comfortable and thus contribute to a long service life of your pump.
Pump filter
Upstream pump filters reduce the contamination of the pump mechanism and protect against damage or reduction of power by oversized solid parts.
Electronic pressure switches
A pressure switch is mounted in the pressure line and switches the pump on and off as required. In the event of a pressure drop due to water withdrawal, the pressure switch automatically switches the pump on and switches it off again when the pressure rises by closing the tap. Many pressure switches are also equipped with a dry run protection.
Dry-running protection
The dry run protection is located in the pressure line like a pressure switch and ensures that the downstream pump is switched off or not switched on in the event of insufficient pressure. This prevents the pump from running dry in case of insufficient water supply and thus from being damaged. However, a sudden loss of pressure in the pressure line (pipe breakage) is also detected and the pump is switched off.
Float Switches
A float switch for water pumps is used to switch a pump on or off. It is waterproof and floats on or in the pumped medium. Due to the free length of the connection cable, it is possible to define exactly at which water levels should be switched on and off. Depending on the switching function, float switches can be used for "filling" (switch contact is opened for a float switch aligned upwards) or for "emptying" (switch contact is opened for a float switch hanging downwards). Float switch with changer function can be used for both tasks.
Suction hose
A suction hose is a ready-made hose for the suction side of e.g. Garden pumps. This hose is under pressure resistant. A garden hose is not suitable for this purpose. At one end there is a foot valve, which prevents the pre-filled suction pipe from running empty and only opens as soon as the pump draws in water.
Dimensions
The pump connections, threaded fittings and hoses are often specified in inches. However, since measurements must be made in metric units as of 01.01.2010 according to statutory regulations (European Union uniform regulation), this may lead to confusion. For this reason, we have provided the most common sizes in both units of measurement in the following table:
Please note that any measuring and manufacturer tolerances must be taken into account. The respective outer diameter of the hose depends on the wall thickness.