Comparison Optima 2.5SDm 1.5/18 vs Optima 3.5SDm 2/9

The maximum amount of water that the pump can deliver from the well per unit of time. The choice for this parameter depends on two main points: the maximum total consumption and productivity of the well.

The maximum total consumption is the amount of water that is necessary for the simultaneous normal operation of all points of water intake in the system. Different types of consumers (washbasins, showers, washing machines, etc.) require different amounts of water; exact values can be found in special tables or instructions for specific models of household appliances. And the total consumption can be calculated by adding the indicators of all points of water intake. As for the productivity of the well, this is the maximum amount of water that the well can produce in a certain time without draining it. This indicator is usually indicated in the documents for the well; if it is unknown, before buying a permanent pump, it is imperative to determine the productivity — for example, by trial pumping with an inexpensive unit.

Accordingly, the performance of the pump should not exceed the productivity of the well, and it should be at least 50% of the maximum total consumption of the connected water supply system. The first rule allows you to avoid draining the pump and the troubles associated with it, and compliance with the second guarantees a normal amount of water even with a rather intensive water intake. And, of course, do not forget that high performance requires high power and affects the cost of the device.

The maximum head is the maximum height to which the pump can raise water during operation (the highest height of the water column that it can support). This parameter describes the pressure created during operation, but since the operation of well pumps is directly related mainly to lifting liquid to a great height, it is easier to use head data in metres than pressure data. However, if necessary, one can be easily translated into another — 10 m of pressure corresponding to a pressure of 1 bar.

When choosing a pump for this parameter, it is not necessary to chase a large pressure, but it is necessary to take into account several factors.

The first of these is the actual height to which the water must be raised; it can be determined by adding the immersion depth of the pump and the height of the highest draw-off point above the ground. The immersion depth is displayed taking into account the so-called dynamic water level in the well — i.e. distance from the surface of the earth to the water surface during continuous operation of the pump (this indicator is greater than the static level, since when the water is pumped out, its level decreases). The dynamic level is usually indicated in the well passport; the pump should be at least a metre deep underwater, plus a margin of 2 – 3 m should be taken as an adjustment for seasonal level fluctuations. Accordingly, for a well with a dynamic depth of 40 m, supplying a house with...an upper draw-off point of 6 m above the ground, the total height difference will be at least 40 + 6 + 4 = 50 m.

The second point is the hydraulic resistance of the system. Even with horizontal pipes, pressure is required to move fluid through them; usually, when calculating, it is assumed that for every 10 m of the pipeline, 0.1 bar, or 1 m of head, is required. For a water supply system inside an average house, resistance losses are about 5 m of head (0.5 bar). Accordingly, if in our example the house is located 10 m from the well, then the margin to overcome the resistance should be at least 1 + 5 = 6 m of head.

And the third point is the pressure at the points of water intake because the pump must not only “push” the water to the tap, but also provide pressure at the outlet. Here, the optimal values may be different depending on the situation. For example, let's take at least 1 atm (1 bar), which corresponds to 10 m of pressure.

Thus, in our example, the pump head must be at least 50 m (height difference) + 6 m (resistance) + 10 m (outlet head) = 66 m. Of course, this is a calculation for the most general case; in special situations, the formulas may differ, so it makes sense to refer to special sources for them.

Number of suction stages.

Single-stage systems assume the presence of one impeller or other similar element, while multi-stage systems — several. The latter makes it possible to obtain a strong water pressure with an overall compact size.

The size of the pump outlet, more precisely, the size of the hose mount provided on this hole. In plumbing, these sizes are traditionally denoted in inches and fractions of an inch (for example, 2" or 3/4").

Usually, the higher the pump performance (see the relevant paragraph), the larger the hole is provided in the design (so that a large amount of water can pass through it freely). Ideally, the dimensions of the outlet should match the dimensions of the mount on the hose; if there is a mismatch, the situation, of course, can be corrected by using adapters, but this option has its nuances and is not always applicable. In deep well pumps, the following values are considered: 3/4", 1'", 1 1/4", 2", 2 1/2" and 3". There are also more exclusive ones, such as 1 1/2", 4" and 5".

The highest suction water temperature at which the pump can operate normally. For deep well pumps, the water temperature is also important because the pump is constantly immersed in water during operation, and the liquid provides cooling. Therefore, in modern models, performance indicators are usually low — less than 30-35 °C. However, the temperature in artesian wells, usually, is much lower (the only exceptions are regions with thermal waters, but specific equipment is used there).

The power consumed by the pump motor during operation. A more powerful engine can provide more head and performance, but these parameters are not directly related: two models of similar power can differ markedly in practical characteristics. Therefore, this parameter is secondary, and more or less unambiguously it describes only the class of the unit as a whole — powerful engines are typical for high-end performant models. But what this characteristic directly affects is the actual power consumption; and with it, in turn, are connected not only to electricity bills but also connection requirements.