outsider:
Well, I don't believe that will solve your problem, you could try pulling 1 pump at a time out, looking for a defective one and replace it with a non submersible type with a plastic suction pipe.
Or easier, disable the relay to each pump in turn.
non of these suggestions are acceptable options for me. it dont matter what pump i plug in they all do the same thing to the sensor. i believe it is some sort of magnetic interference. i need somthing to break the ground loop with the arduino and ph sensor module. this clearly is not the place to ask this question.