Which type of soil holds onto the most water? You fill three pots with sand, clay, and silt, dry them in the sun for two days, then pour 200 ml of water into each pot. After four hours of draining, you measure the water that passed through and weigh each pot again. Sand lets almost all the water through. Clay holds a moderate amount. Silt retains the most water, showing the smallest volume in the collection container and the largest weight gain. The particle size of each soil type controls how tightly it grips water.