Hi Paul. Good idea about a new thread.

Is the system sealed? If so then the HHO can't float up because there's no denser fluid (air) floating down to displace it.

If it's open to the air, and air sinks down the pipe to push the HHO up, then you have a higher pressure at the bottom than the top. The higher the tower, the more pressure, so the more energy needed to create the HHO. You told me yourself that HHO generation requires more energy at higher pressures.

I think we'll be running in circles until we can quantify it.

Or just build one! Look how cheap and simple it is!! Some bits of wire in a pipe, a water wheel, an old lawnmower motor and an alternator from the car wreckers.