This did not happen to me personally but I heard the story straight from the horses mouth.  One of our trouble shooters got a call one night and he drove out to this ladies house out in a rural area.  He asked her what the problem was and she said every time she flushed the toilet the lights would almost go out in the small frame house that she live in.  Sure enough she flushed the toilet and the lights went real dim.  Well Walter, having worked all day looked over the house real good and checked the voltage at the meter and it was good.  He had looked everywhere he could think of and checked everything and found nothing.  So, he told her she needed to call a plumber.  She called a plumber and the plumber came out and he told her she needed to call an electrician.  Well she called an electrician and he finally found the problem.  The ground to the water pump in the well had broken and the pump was using the house ground for its source.  Walter or someone did a follow up on that the next day and made sure she found the problem,  that is how we found out what had happened.