A pump located beside the systern pumps the water up to the holding tanks on the roof. These tanks are connected to your hot water boiler and all the taps in the house. Because the tanks are on the roof you get gravity fed water pressure.
If you use up all the water in the holding tank you will have to wait for the systern to fill up again in the night (or buy a bigger holding tank).
Maintenance Tip: There are 2 "floatadores" or electric switches. One in the systern at ground level and another in the roof tank.
These switches are encased in a plastic water tight housing.
When the roof tank gets low on water, the switch turns on and "requests" water from the systern. If the systern has water its switch will also be in the "on" position. Thus the pump will start.
If the systern gets low on water its switch will turn off and the pump will stop. OR if the roof tank gets close to full it will break the connection and stop the pump. The switches need to be adjusted by dangling them on the end of their electrical cable. If you look carefully at the above picture you will see a tiny switch floating in the water just under the white float. When the systern is almost empty, that switch will be dangling in the vertical position if the cable is short enough.
By the way, that white thing floating in the water works just like a toilet valve. It physically shuts off the incoming city water when the systern is full.
The entire system of delivering water to your condo, house, or apartment is radically different than in Canada/Europe/US. The city delivers water in the nightime only and with low pressure lines. This water is for bathing, dishes, and for washing clothes - not for drinking!
You will have a systern on the main floor of the building (left). It is this tank that gets filled during the night.
Buy drinking water from the street vendors for only 18 pesos. Walmart has a nice base with a tap for 95 pesos.