In our building we have a large water tank located on the ground floor and a pump (this one: https://www.pedrollo.com/public/allegati/DG%20PED_EN_50Hz.pdf ) that feeds water to the smaller tanks (one for each apartment) that are located on the roof.
This pump is consistently activated every 5 seconds when it is set to its 3 bar setting. It does that 24/7. When I increase the setting it is activated more frequently and when I decrease the setting less frequently. After it is activated it runs for about 5 seconds and stops. It doesn't appear to overheat because when it stops the LED panel lights up as expected, showing the pressure that was reached.
This pump also feeds the water that goes directly to the apartments (the water that doesn't go to the roof tanks). This direct water correctly responds to the pump's setting which means that the pump correctly regulates the pressure.
Right after the output valve of the pump the water meters for all apartments are installed. When the pump is working I can see that none of the water meters are moving, which means no water is actually moving when the pump is working. (Of course, there are cases where some water meters are moving when that apartment's tank is being filled).
When I close the output valve of the pump it stops being activated.
The possibility of leaks is excluded because if the pump was filling leaks we would see some water meter moving.
The possibility of a failed input valve to the pump is excluded because if this was the case the pump would still activate when its output valve was closed.
The possibility of the air bladder being bad is excluded because the water pressure that the pump regulates appears correct.
Now, all the above conclusions are my non-plumber opinions. My question is: What could be the reason that the pump is activated so frequently?