That is a bad idea. Hydrocarbon polymers like PEX, ferrous alloys, and concrete would be much more practical.

I think people are missing the joke, but gold sewer pipes is amusing to consider.

45lbs of gold would get you a ten foot-ish 1 in ID plumbing pipe.

... and we already have a problem with copper theft.

In fairness, after hundreds of years of people trying to turn lead into gold, this might be one of the more practical attempts.

Well played.