Hey Bin,
If you havent done this before, then follow this, shutdown the Valve first then open the faucet from both sides upwards and downwards. If you still need more information you can possibly get ... read more
Sounds like inadequate venting for the drain lines. Could have been build this way or maybe a clog has developed in the vent pipe. Such as birds or squrrels building a nest in the vent pipe up on the ... read more