Repairing a flush tank can involve different steps depending on the specific issue. Here are some common problems and their solutions:

1. Weak or incomplete flush: If the flush is weak or incomplete, it could be due to a clogged flush valve or a worn-out flapper. To fix this, turn off the water supply valve and flush the toilet to empty the tank. Remove the flush valve and clean it thoroughly with a brush and water. If the flapper is worn out, replace it with a new one.

2. Constant running water: If you hear a continuous running sound coming from the tank, it could be due to a faulty fill valve or a leaky flapper. To fix this, turn off the water supply valve and remove the tank lid. Adjust the fill valve height to the manufacturer's recommended level, or replace it with a new one. Check the flapper for any leaks or wear and replace it if necessary.

3. Leaking tank: If you notice water pooling around the base of the tank, it could be due to a cracked or damaged tank. In this case, you will need to replace the tank. Turn off the water supply valve and flush the toilet to empty the tank. Remove the bolts that secure the tank to the bowl and carefully lift the tank off the bowl. Replace the tank with a new one and reattach it to the bowl with the bolts.

4. Loose or wobbly tank: If the tank is loose or wobbly, it could be due to loose or damaged tank bolts or washers. Turn off the water supply valve and flush the toilet to empty the tank. Tighten the bolts and washers that secure the tank to the bowl. If the bolts or washers are damaged, replace them with new ones.

By following these steps, you should be able to repair a flush tank. However, if you're not comfortable with plumbing work, it may be best to hire a professional plumber from Locals4u to help with the repair.