Pardon me if my term catchment is not correct. I was watching the Travel Channel when I heard that while showing the (unelevated) water tanks. Those are storage for rainwater that they use for irrigation and washing to save on tap water. When we were in the province of Batanes, there was a house with a rain catchment that was made of concrete. A small manual pump is connected to draw water. I have posted this thread because we are thinking of having our own rain catchment tank because we are having lots of rains in the past few days. In fact, our extended garden is flooded again. It's a good thing that the corn is already harvested. The only issue now is the cost of the installation of the tank.