The drain valve of the toilet tank leaks and is not blocked. Is it loose? I feel that pressing the big semicircle drained the water at once, and then it leaked and was not filled with water.

First prove whether there is any problem with the water pipe valve.

Close the water pipe valve tightly and see if the other water pipes can't get out.

Then prove whether there is water leakage inside the toilet, and close the water pipe valve for a long time to see if the water level in the toilet tank has dropped.

If there is a decrease, it is that the joint between the drain valve and the water tank of the toilet is loose.

See if the toilet drain is aligned with the sewer drain.

At present, there are two drains at the bottom of the toilet, which is convenient for installation.

It is also possible that there is water where the ground connects with the toilet.

Once again, it is proved that the sound from other water pipes should be intermittent and impossible to be continuous.

The first feeling of sound is usually the sound coming from above.

Put your ear close to the main sewer and listen to the sound inside. If the sound frequency inside is the same as that under the toilet, this possibility cannot be ruled out.