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.
Suction type
The main division in this parameter is related to whether the pump can remove air from the suction line. This, in turn, determines the features of starting the unit.
— Self-priming. Self-priming pumps include all pumps that do not require the complete absence of air in the suction line at startup — it is enough that the pump itself is filled with water. Accordingly, such models are less demanding and normally tolerate air entering the line. However, this requires a reliable design that can normally withstand water hammer, which accordingly affects the cost of the unit.
— Priming. Pumps with this device can only work normally when both the unit body and the suction line are filled with water. If air enters the line, it must be removed or the pump will not be able to start normally. Such models are not as convenient as self-priming ones; at the same time, they are noticeably cheaper, and with the normal quality of the water supply system, there is practically no significant difference between the two varieties.
Maximum immersion depth
The maximum depth at which a submersible pump can be placed without the risk of failure or breakdown. It is usually indicated for fresh water, so in fact it is advisable not to lower the pump to the maximum depth level — after all, the density of the pumped liquid may be greater, which will create off-design loads on the structure.
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.
Maximum liquid temperature
The highest temperature of water at which the pump is capable of operating normally. Usually, in most models this parameter is 35-40 °C — at high temperatures it is difficult to ensure effective cooling of the engine and moving parts, and in fact, such conditions are rare.
Outlet size
The thread size for connecting a hose or pipe to the pump outlet. If there is a branch pipe with an external thread in the design, the size is indicated for it; if not, for the internal thread of the inlet.
Anyway, the dimensions of the pump outlet and the mounts on the hose/pipeline connected to it must match — otherwise, you will have to look for adapters. This size is specified in inches and fractions of an inch.
This parameter is relevant primarily for surface models.
Maximum power
Rated power of the pump motor. The more powerful the engine, the higher the performance of the unit, usually, the greater the pressure, suction height, etc. Of course, these parameters largely depend on other features (primarily the pump type, see above); but models similar in design can be compared in terms of power.
Note that high power, usually, increases the size, weight and cost of the pump, and also implies high costs of electricity or fuel (see "Power source"). Therefore, it is worth choosing a pump according to this parameter taking into account the specific situation; more detailed recommendations can be found in special sources.
Protection class (IP)
An indicator that determines the degree of protection of dangerous (moving and current-carrying) parts of the hardware of the pump from adverse effects, namely solid objects and water. Since pumps, by definition, are used for pumping liquids, and many of them can normally pass quite large particles, in this case, we are talking about protection against moisture and foreign objects from outside.
The level of protection is usually indicated by a marking of the letters IP and two numbers, the first of which indicates protection against the effects of solid objects, and the second — against the ingress of water.
For the first digit, each value corresponds to the following protection values: 1 — protection against objects with a diameter of more than 50 mm (large body surfaces) 2 — against objects with a diameter of more than 12.5 mm (fingers, etc.) 3 — against objects more than 2.5 mm (most tools) 4 — against objects larger than 1 mm (virtually all tools, most wires) 5 — dust-proof (total protection against contact; dust can enter, but does not affect the operation of the device) 6 — dust-proof (case with full dust protection and contact).
For the second digit: 1 — protection against vertically falling drops of water 2 — against drops of water with a deviation of up to 15° from the vertical axis of the device 3 — against drops of water with a deviation of up to 60° from the vertical axis of the device (rain) 4 — against splashes from any direct...ion 5 — from jets from any direction 6 — from sea waves or strong water jets 7 — short-term immersion to a depth of up to 1 m (without the possibility of continuous operation in immersed mode) 8 — long-term immersion to a depth of more than 1 m (with the possibility of permanent operation) in immersed mode).
Note that in some cases one of the numbers can be replaced by the letter X — this means that official certification for the corresponding parameter has not been carried out. In pumps, X is usually put in place of the first digit, because. a high degree of moisture resistance (and for submersible models, for example, it must, by definition, correspond to 8) means a high degree of protection against solid contaminants.
