Thanks everyone. This sets my mind at ease that at least its not going to blow up my system if I drain it too far....
@Czauto, we need the pumps to run as it pumps water to the cows drinking troughs (I'm on a dairy farm).
I've ordered 8 x 550W panels so that should take care of the loads during the day. During the night we rarely have as much usage because neither the cows nor the humans are using water requiring pumps to run...
Thanks everyone..