Any idea on what would cause a loud bang as water is being drawn in from the well pump? The pressure tank and switch system sit in our garage we suddenly heard a loud bang as it kicked on one day . Ordinarily the pressure switch will kick on and you can immediately hear the water coming into the pipes . It kicks off at the correct pressure and there is a light shutter or kick in the pipes as it turns off . However this bang is happening at start up . When the pressure switch clicks it is hesitating just slightly then a loud bang is heard and you hear the water coming through into the pipes it shuts off as normal . We only just heard this one day last week . It started in the morning and continued throughout the day getting louder to the point where if you heard it in the house you actually jumped . And just like that the next day it was gone and working quietly as normal . It has continued to work properly for the last five days and then today suddenly started again having a loud bang on start up . I had noticed that both times it began we were doing laundry, however we did laundry during the four days that it wasn't a problem . The system is 11 years old however we did replace the pressure tank last year. It does not appear to effect the water pressure when this happens however it is obvious that something is going wrong and it can't be good for the pipes .