hey hound.I changed pumps and it's still not holding numbers, things are so out of wack. I took weenie pump out and changed it for a big one, put in the valve before the first water line in my res. set all of the nutrients in res and each module to 5.8 for ph and 300 ppm for babies and the next day my res was 700 and ph of 6.58 and each module was different from not only the res but every other module. I've searched all of the forums and you seem to be the only one having it work. Most others are converting to ebb&flo/Drip combo or putting inline pumps in their line somewhere to kick on periodically to recirculate. General Hydroponics should address this.