If the startup current from a motor fried a GFCI, then the
human who installed that GFCI was defective. In Europe, some
GFCIs are installed for everything in the building - not just
selected circuits. Why then do those GFCIs not fry.
Furthermore, if a motor trips a GFCI on startup, then the
motor has an internal defect; leakage currents that are too
high and that get worse when the motor is started.

At first glance (based only upon limited information
currently posted), the pool has two major failures. First is
massive leakage from the pump into the pool. Second, GFCIs
are not working properly either due to erroneous installation
or due to internal failure. Both primary and second protection
systems have failed.

Bean counter type management convinced themselves that a
little leaking around O'rings also was not a problem. After
all, the proof was in Space Shuttles that did not explode.
However people who deal in reality knew that O'ring leakage
was a problem so serious that space shuttle flights should
have been terminated.

We are suppose to learn basic concepts of life from the
news. However someone even here posted:
is it really all that dangerous? A little tingling never
killed nobody.
This could only be posted by one who never learned even basic
lessons of life from the murder of seven Challenger
astronauts. This is a post typical of someone whose intent in
life is to kill others.

The levees did not break during Betsy and Camile. Therefore
the levees would not break with Katrina. At what point do we
look to humans and say, "There lies the real source of all
problems". A president told us that no one expected the
levees to be breached. At what point do we recognize problems
are due to human failure - from things such as denial.

Same applied to electric tingling in the pool. It is
considered a precursor to human death. Get it fix yesterday.
If this post is too complex, then read Amun's response as
quoted below. Don't be in denial like some presidents and
Thiokol managers that we know. Learn, if from no where else,
from why people were killed. Denial is akin to criminally
negligent homicide - or why accidents are routinely and
directly traceable to human failure. Described are symptoms
of a failure of both the primary and backup protection
systems. Tingling in a pool is that dangerous that every
poster here should have said so.

Meanwhile, I have serious reservations about how the pool
was safety grounded. Grounding may be so in violation of code
as to require (worse case) pool removal. Based upon how the
pool was electrically connected, then a serious evaluation of
pool safety grounding is immediately necessary - and maybe an
investigation so that charges be filed against the person who
installed electrical wiring. The symptoms as described here
are that serious.

No one has died yet. Therefore the system is safe. This is
what everyone is suppose to have learned from the murder of
seven Challenger astronauts.

Amun wrote:
As the OP is already sure the previous owners were nuts.

Don't discount anything.

First,.... GFI breaker or outlets should NEVER be used with motors.
(well pumps and swimming pool filters both use them)
They don't work well.
The starting currents in motors can fry the electronics in a GFI

And a GFI should NEVER be used to fix a "no ground" problem.

And NO gfi is foolproof, they can go bad, and often do and the
test button won't always show a problem

I've seen the same idiots who fixed fuses that kept blowing by
shoving pennies in. Move into breakers and fill the handles with
crazy glue to keep them from tripping.

Make sure all the motors & pump bodies are properly grounded.
swap breakers with known good units.

And don't forget to check any "pool lights" as well

And don't swim in the pool if it tingles, or at least leave a
note for your next of kin to let us know what the final outcome was.

AMUN