After wiring and plumbing everything the next stage was to put it back in its housing, attaching the pressure sensors and wiring everything together. This time more of the power circuitry is inside the unit so only the 12V supply, single 5V supply, 6 control wires for the pumps and valves and the 3 pressure sensor data wires are external. After testing all the connections and relays I could then start the attaching the lid and tubes.
After putting a little water in each of the tubes I was happy to find that everything appeared to be working. The self priming pumps took a little while to start moving water but when they did, they moved it nice and quickly. The pressure sensors needed a bit of calibrating because they were not positioned the same way as before.
Not finding any leaks I made the pumps fill the tubes as far as they could with the water already in the system and then filled it the rest of the way, the theory being that there physically isn’t enough water in each tube’s reservoir to overfill the tube, even if everything goes horribly wrong with the control system.