A sign forbidding anyone to enter the house.

Here are some possible slogan suggestions to stop people from pouring water into the trash can:

1. Please don't pour water into the trash can. Thank you for your cooperation.

2. Keep the environment dry and don't pour water into the trash can.

It is forbidden to pour water here. Thank you for your cooperation.

It is only used for taking out garbage, and it is forbidden to pour water.

In order to protect the environment, please don't pour water into the trash can.

6. The trash can is only used to hold garbage. Please don't pour liquid into it.

7. For the sake of public health and beautiful environment, please don't pour water into the trash can.

8. Keep the trash can dry to prevent bacteria from growing. Thank you for your cooperation.

9. Dumping water may cause environmental pollution. Please don't pour water into the trash can.

10. For the health of you and others, please don't pour water into the trash can.

These slogans aim to prevent people from pouring water into the trash can by providing clear and friendly instructions. Choose a slogan that suits your situation and make sure it is where people can easily see it.