"George" wrote in message news:X0gfe.63729$WI3.37219@attbi_s71...
I am taking from above that you did not read the original poster...
His 48VAC reading was even after he has unplugged all his devices.

Please read his original words

Could you explain then how GFCI could influence his voltage readings ?

No, what he said was "I measured the AC voltage from the copper inlet pipe to
the tank water -- by sticking the probe into the water. Was I surprised. I
measured 48 VOLTS AC !!!! I then began unplugging equipment. "

So he unplugged equipment 'after' he measured 48 volts, which means that
equipment was leaking current into the tank. He then proceeded to describe the
voltage he got after he unplugged various appliances.

You have stopped your reading too soon. He wrote:
"When EVERYTHING was unplugged - I still had a reading of 32 Volts AC."
I admit, I mentioned incorrectly 48V, but 32VAC makes not a big difference.
When all devices are unpluged we have the proof that 32VAC is NOT coming
from these devices. And GFCI will not change the readings.

We can make some efforts to explain what is the possible source of
his 32VAC but this is a different story... It could be even his
local radio station and his tank acts like an RF antenna...
It does not matter. His high impedance voltmeter will pick up
any voltages, even from the air, and it does not mean his devices
are leaking electricity, what was prooven with unplugging them all
and still recording non-zero reading.

I suspect that if he plugs all of the same
equipment (the ones that showed voltage leakage according to his measurements)
into that GFCI, it will trip the circuit, shutting off the power. He will
likely have to replace some of this equipment in order to prevent the GFCI from
tripping.

And I will bet that everything is fine with his devices, George.
His measurement method is wrong! If he had any device leaking,
his high-impedance voltmeter would show voltage close to 120VAC
and only when the suspected device is plugged to the mains.