Possible causes: 1) Aging or damaged internal tank components (such as flushing parts) leading to insufficient water. 2) Clogging inside the pipe or toilet due to dirt. 3) Misalignment or aging of the flange. Solutions: 1) Replace the damaged flushing components inside the tank (such as the drain valve or button). 2) Use a pipe cleaner to soak and then flush, or use an unblocker to clear the blockage. 3) If the flange is damaged, dismantle the toilet and replace the damaged flange with a new one to ensure sealing.

Possible causes: 1) Aging or loose seal ring in the drain. 2) Cracked caulk at the connection between the sink and the countertop (common in under-mount sinks). 3) Loose angle valve or water inlet pipe joint.

Solutions: 1) Replace the seal ring in the drain or replace the entire drain. 2) Remove old caulk and reapply neutral mildew-proof caulk for fixation (for under-mount sinks, consider installing support brackets). 3) Tighten the angle valve joint or replace the inlet pipes that have aged. Professional assistance is recommended.

Possible causes: 1) Use of hard cleaning tools (such as steel wool) for scrubbing. 2) Corrosion of the glaze by strong acidic or alkaline detergents. 3) Impact from heavy objects causing chips or cracks.

Solutions: 1) Use a ceramic repair agent to fill minor scratches, and then polish them; for severe damage, replace the damaged sanitary ware. 2) Use neutral detergents with a soft cloth for daily cleaning. Avoid corrosive products. 3) Do not place heavy objects on the basin to prevent impact.

Possible causes: 1) Long-term accumulation of hair and debris. 2) Buildup of grime on pipe walls slowing drainage. 3) Misalignment or poor design of the trap during installation.

Solutions: 1) Use a drain cleaner or a plumbing snake to clear blockages regularly. 2) Disassemble and rinse the drainpipe, and check and adjust the trap if needed. 3) Ensure pipes are aligned during installation to avoid sharp bends.