Hi Boonyu ,

I have a unit which at 3 level below from the breaktank but still exposed to noise every hour and every second . You will experinces the noise from pump like humming sound and water flow sound or bangging sound from the pump room if the room not have proper treatment .  the water pump will running 24 hour due to high usage for whole building so the noise will not stop and if the pump room without noise and vibration treatment  , you will possible will listen the humming noise from pump room every second . The low frequency vibration generate from pump will transfer the noise to the near by unit follow the wall structure and if long term exposure will cause the health issue such like sleeping disturb and hypertention .

As you said the breaktank opposite the parcel unit , so you need to see the exhaust fan location as well , the exhaust fan also could generate noise in the corridor if position on the corridor .

Of course this is depend the quality of developer . If they have proper treatment the room and consider the noise and vibration issue most of time should be no issue when select the near by breaktank . 

Hope this advise will enough for you and answer your question .