If this were true, every hot tub everywhere would be having this issue, no?You also must look into whether the hot tub is EXCESSIVELY insulated to ground.
My Brother in Law faced this issue.
What can happen is that current/ charge can be induce directly into the swirling water... something first noted by Faraday.
For the water is ionized by body sweat, which keeps rising over time, until the HO flushes it all out.
You'd be astounded as to how salty a hot tub can get, as the water keeps evaporating and the HO keeps refilling it.
You're getting a dose of salts from the potable water, too.
So what happens is that, at first, there's no problem at all.
Then, ever so gradually, the HO notices that he's getting hit with jolts to the groin when he straddles the hot tub and the surrounding surface.
In my BiL's case, I measured 45 volts. (!!!)
The actual current involved is trivial, BTW.
I made everything go away by dropping a copper wire into the water and running it off to the GEC System.
Poof, the volts dropped to zero... and stayed that way.
Naturally, everyone wants to know how the effect gets rolling.
1) The motor is not contained within a Faraday box// shield.
2) The circulating pump injects salty water ( it's ionized, of course ) right through the magnetic field of the motor driving the pump.
3) A feeble amount of energy is then transferred to the Na+ and Cl- ions.
4) It has no where to go, so it starts to become a bucket of capacitance.
This process bears no small resemblance to the headache of phantom voltages often seen with Romex cables.
In the ghost voltage case, you're dealing with capacitive coupling.
When you pass a conductor through a magnetic field, energy is transferred.
In the hot tub, the conductor is the 'brine' -- not copper, not metal.
The energy transference is pathetic in this instance.
But when the discharge of said energy is through your groin, you sure do notice.
I've lost count for the number of times e-men hit the Internet with this exact same 'trouble.'
I am not claiming that this is your problem, here.
It's just something that you need to be aware of... before you go insane.
If a bonding/grounding conductor makes the voltage evaporate... and after it's removed ( the wire ) the voltage difference stays at zero... but comes back days or weeks later... ever rising...
Well, now you know.
The effect is proportional to pump run time, under cut by charge bleed-off by any means.
It's ironic, the manufacturer went to extreme lengths to isolate, electrically, the hot tub's water from the outside world.
Which is what triggers this effect.
Flushing the water back down to really, really fresh also cuts this effect way, way back.