You will need
The average calculation is based on the fact that each point consumes of 0.6 of a cube of water per hour. If the house is 6 points, total water use calculate: a 0.6 × 4 = 2.4 cubic meter per hour. When calculating, consider that out of 6 points at the same time can work only 4.
The required pressure determine by the formula: N = 10Рпт + NP + Geo, where RPT is the desired consumer pressure (not less than 2 atmospheres), Neo the difference in the levels of the consumer and the water level, NP — losses of the magnitude of the pressure in pipelines (average for 10 m of pipe is 1 metre water column).
Conditions for example: the required pressure is 3 atmospheres, the house has 4 points of water separation (3 of them can work simultaneously), the difference between the levels of consumers and water is 40 meters, and the loss in the pipes is 4 meter. First, calculate the required volumetric flow (performance pump). For this 3 (the number of simultaneous points) and multiply by 0.6 for average water consumption at a single point within the hour). You'll get maximum water flow of 1.8 cubic meters per hour.
Then multiply 3 (the desired value of water head) for 10, add 4 (the size of losses in pipelines). To get the amount, add 40 (the difference between the water and the necessary level at which the pump must lift water). The result is the value of the water head in metres, i.e. the distance that the pump must provide a lift of water. In this case it is 74 meters. After determining the required pressure you need to add a little more, that is, to choose a pump with a small margin of power.
Knowing the required performance and the desired pressure, it is quite easy to choose a suitable power model of the pump.