Kind of curious about how much ammonia you are reading?
If your water company is feeding ammonia it is for the sole purpose of creating chloramines. Chloramines last longer out in the system an also help to reduce the chlorine smell from your water. Normally they want to keep the free ammonia down to a fraction of a ppm
. If you are seeing an elevated reading it would not hurt to give them a call anyway. Too much ammonia in the water mains can cause the same thing that happens in our tanks, nitrifying bacteria can start to grow. Plus it means they are wasting ammonia.