That's okay, I think the IRQ0 port of the Arduino Mega 1280 is digital Pin 22. I ran your sketch and got something: when no liquid is flowing through, all stats are on 0, and when liquid flows through it rises to 0.0010.. What does this means? Thanks!
KWH: 0.0000 0.0000
KWH: 0.0000 0.0000
KWH: 0.0000 0.0000
KWH: 0.0000 0.0000
KWH: 0.0000 0.0000
KWH: 0.0000 0.0010
KWH: 0.0000 0.0010
KWH: 0.0000 0.0010
KWH: 0.0000 0.0010