It relies on the principle of pumping from high to low as a work that relies on the raengkrachak of water and air pressure, which is an important factor is to make the water tank vacuum. B. gravity between the molecules and the weight of the water plus gravity. Cause water pressure, and one of the indispensable factors. Transfer of the liquid pipe system is the need to have the appropriate size to achieve raengkrachak of water because of the way the water pipes to a larger size. Drain water.