Two flow sensors, one ESP32, LCD and/or Arduino I want to build a flow meter but the Gal/Min rating of something like this flow meter is too low. I am thinking of strapping two side by side with suitable plenums for In and Out. 

I have found some sketches like this but wondering how to use the two inputs to aggregate the results to GPM and Gallons total for display on an LCD screen. I am unsure what happens if two Hall-results arrive at or about the same time but on different Data Pins.

I have priced some single sensors with a higher flow rate for the pipe size but they run to several hundred dollars. Gallons are not critical as long as I can be within about 5% error over ten minutes, our average tank fill time.

Can someone please point me at some code to get me started for an ESP32 and LCD. I'd even consider adding a Nano if that makes things easier. I imagine that would certainly prevent collision issues. Basically I need to be able to handle the flow rate to a single LCD.

Thanks
A Hall Effect Sensor like that just gives you a pulse every rotation (or two pulses per rotation, etc) of the internal vanes.

If you use interrupts to count the pulses then two pulses arriving at the same time will be handled sequentially. The interrupt flag indicating a pulse has arrived is set in hardware the moment the pulse arrives, and the CPU checks all the interrupt flags between instructions. Each flag is handled sequentially, the order determined by interrupt priority settings and a "natural" order determined by the internal wiring of the CPU.

However there is a better way on the ESP32, and that is the Pulse Counter peripheral.  This is designed to count pulses like the signals from Hall Effect sensors. 

You can just leave the Pulse Counter counting your pulses, then periodically read and reset the pulse count to see how much water has flowed in that period. It looks from the documentation that you can have two inputs both making the same counter increment, so it will do the aggregating for you.