Steve..Our tank is 3 meters long,2 meters wide and 2 meters deep divided into 3 chambers..This is the size that local building standards demand and should last 25 years at least for a domestic house (probably 35-50 years)
Our water is from the Barangay system and costs us 10 Pesos per cubic meter..The pressure we get feeds our tanks in the loft ..Gravity takes care of the rest..
Some areas demand that you drill your own deep well which needs to be connected to a pump and a pressure tank to feed your supply... One of my drinking buddies has a drilling business and says the average job including pump and pressure tank costs 60k PHP... All depends how deep the water is situated..
Cheers,
Fred.