To remove water stains from limestone kitchen counters, follow these steps:

1. Clean the countertop with warm water and a mild soap to remove any dirt or debris.

2. Mix equal parts baking soda and water to create a paste. Apply the paste to the water stain.

3. Cover the paste with plastic wrap and let it sit for 24-48 hours.

4. Remove the plastic wrap and wipe away the baking soda paste with a damp cloth.

5. If the water stain is still visible, mix equal parts hydrogen peroxide and ammonia in a bowl. Use a soft cloth to apply the mixture to the water stain.

6. Cover the area with plastic wrap and let it sit for 24 hours.

7. Remove the plastic wrap and wipe away the mixture with a damp cloth.

8. Rinse the countertop with warm water and dry with a clean cloth.

Note: Be sure to handle chemicals with care, wear gloves and ensure the room is well ventilated.