100 year old house, multiple water supply updates. While downstairs powder room is gutted I was tracing the latest copper pipe upgrade with the idea to at least replace some of the hot water lines to speed deliver to sink taps probably with PEX. Downstairs powder room hot supply to sink is 3/4 inch main trunk, up one wall, across ceiling where it's reduced to 1/2 copper, down the opposite wall and then down into the crawl space after branching off to the sink. Couldn't figure out why it went back down to the crawl space so investigated this morning. It makes an immediate 90 degree turn back to the main COLD water supply trunk . Old houses are fun.