Now I can confirm that the pipe of the central heating system through the kang has sprung a leak . The second day after plastering the cleared kang mother found something had got wrong with the facilities when she had lit the stove and heard a loud bubbling sound from the mouth above. Then she stopped adding fuels to the stove. She thought the water in it might have been short. Yesterday when the same thing happened again, I began to fill up the pipe with water. It was strange that the radiators seemed to have been empty for it took me a long time to refill the pipe.