Improve toilet flush power by adjusting the tank water level to one inch below the overflow tube. Clean clogged rim jets under the toilet bowl with a wire hanger or vinegar. Replace a worn flapper that closes too quickly. Check for partial drain line obstructions reducing suction. Adjust the flapper chain for proper lift. For older low-flow toilets upgrading to a modern pressure-assisted or dual-flush model dramatically improves flushing performance. Ensure the vent pipe on the roof is clear.