But is there any risk to you being in the path of least resistance? All your pipes are connected (to the ground) so why would the electricity not take the readily available metal path?
A typical lightning bolt is about 300 million Volts and about 30,000 Amps. Since even the best-grounded home certainly can't sink 30,000 amps of current into the neutral-bonded earth bar, it has to go somewhere. It finds multiple paths, and the current is shared between them. There's also the conversion to heat in all those insufficient conductors, etc.
[0]:https://www.independent.co.uk/news/science/is-it-safe-to-tak...
And since the water and sewage systems are plumbing systems and not electrical systems, its highly likely they'd be at different electrical potentials in a strike.
Either way should be easy to test. Run the showers and excite the paratoner.