Maximum performance
The maximum volume of water that the device can pump in a certain amount of time. It is one of the key specs of any pump because characterizes the volume of water with which the device can work. At the same time, it does not always make sense to pursue maximum performance — after all, it significantly affects the dimensions and weight of the unit.
Some formulas allow you to derive optimal performance values for different situations. So, if the pump is designed to supply water to water intake points, its minimum required performance should not be lower than the highest total flow rate; if desired, a margin of 20-30% can be added to this value. And for sewer models (see "Suitable for"), everything will depend on the volume of wastewater. More detailed recommendations for choosing a pump depending on performance can be found in special sources.
Maximum head
The maximum head generated by the pump. This parameter is most often indicated in meters, by the height of the water column that the unit can create — in other words, by the height to which it can supply water. You can estimate the pressure created by the pump using a simple formula: every 10 m of head corresponds to a pressure of 1 bar.
It is worth choosing a pump according to this parameter, taking into account the height to which it should supply water, as well as adjusting for losses and the need for pressure in the water supply. To do this, it is necessary to determine the difference in height between the water level and the highest point of water intake, add another 10 to 30 m to this figure (depending on the pressure that needs to be obtained in the water supply), and multiply the result by 1.1 — this will be the minimum pressure required.
Mechanical impurities
The maximum amount of mechanical impurities in the suction water at which the pump can operate normally (of course, if the particles of these impurities do not exceed the maximum size possible for this model; see above for details). Pure water is considered to be water with an impurity content of up to 20 g per cubic meter, but in sewage, the bill can already go to tens of kilograms per cubic meter.
pH value
The pH value of the pumped liquid for which the pump is designed. This indicator describes the level of acidity of the medium, roughly speaking, how reactive it is to the “acidic” or “alkaline” side: low pH values correspond to an acidic environment, and high pH values are alkaline. Acid and alkaline have different effects on the materials used in the construction of various equipment, including pumps. Therefore, when designing parts in direct contact with the liquid, the pH level must be taken into account, and the use of the pump with unsuitable substances is not recommended — this can lead to corrosion, which affects the composition of the pumped liquid and reduces the life of the unit. However, this parameter is critical mainly for specialized models such as pumps for chemical liquids or sewage (see "Suitable for"). In ordinary water (even dirty) the pH range is not so extensive that it cannot be covered entirely.
Dry run protection
A system that protects the unit from running without water.
The dry running mode is abnormal for any pump: at best, the mechanism of the unit in this mode experiences increased loads, and at worst, the device may fail and even a serious accident. This feature allows you to prevent such consequences. The specific method of protection against dry running may be different; one of the most popular options is a float switch (see below). However, in addition, flow sensors, pressure or level switches can be used. These details depend both on the general type of pump and on the specific model; they should be specified separately in each case.
Float switch
The presence of a float switch in the design of the unit.
The operation of such a switch is based on a sensor in the form of a float, which determines the level of the pumped liquid. At the same time, such a sensor can perform several functions at once. The main one is the protection of the pump from dry running: when the liquid level drops critically, the sensor turns off the pump, preventing air from entering the line and helping to save energy. In addition, the float can be used as an overflow sensor (warning of a critical increase in the liquid level), and in some models also as a general-level sensor (reporting the actual amount of liquid).
Power cord length
The length of the cable that supplies electricity to the pump with the appropriate type of power supply (see above). The longer the cable the farther from the socket or other power source you can install the pump. This parameter is especially important for submersible models: if the cable is too short, it will simply be impossible to lower the pump to the maximum depth provided for by its design, because ordinary extension cords cannot be immersed in water.
Pump housing material
The material from which the pump housing is made. It is a structural element in which the working mechanism (impeller or auger) is installed. Note that the motor casing can be made of a different material — this is not important in this case; and in water pumps with the engine (see “Power source”), we are talking about the casing of the pump itself, and not about the support frame in which it is fixed.
The following options are most popular nowadays:
— Plastic. Inexpensive material that perfectly resists moisture and is not subject to corrosion. However, the reliability of plastic as a whole is not very high; the exception is special high-strength grades, but they are extremely rare in pumps (when strength is needed, metals are usually used). So plastic housing is mainly equipped with relatively simple and affordable models that are not designed for serious loads.
— Cast iron. An extremely popular material nowadays: cast iron is strong, reliable, durable and at the same time has a relatively low cost. However, in terms of corrosion resistance, this material is inferior to stainless steel (see below). Nevertheless, subject to the rules for operating the pump, the service life of the cast-iron housing is not inferior to the service life of most of the main components of the unit. Also note that such cases are quite massive, which makes transportation difficult; however, in some cases, a large weight is an advantage: it helps to dampen vibrati...ons.
— Stainless steel. By the name, one of the key advantages of stainless steel is high resistance to corrosion — and, accordingly, reliability and durability. On the other hand, this material also costs a little more than the same cast iron. The weight of such housing is somewhat less — this, again, can be both an advantage and a disadvantage, depending on the situation.
— Aluminium. Premium material. The aluminium alloys used in today's pumps are light, strong, durable, and virtually impervious to moisture, but cost accordingly.
— Brass. A fairly rare option found in some models of surface pumps. Brass is strong enough, reliable and resistant to moisture, but in most cases, it does not have key advantages over the same stainless steel or aluminium but costs a little more.
— Bronze. Another material similar to the brass described above is durable and practical but rarely used.
— Ceramics. A material found exclusively in sewage pumps in the form of toilet bowls (see "Pump design"). Most often, ceramics means vitreous china or more expensive and durable vitreous china — that is, the same materials as in ordinary toilets without built-in pumps.
