Checking what you have
Look at the pipe showing under your sinks and next to the heater, and jot down what you see. That alone tells us a good deal.
From your construction year and what has already been replaced we judge the scope, a single branch or every fixture in the house.
Routing for Colorado winters
The places on our list had roughly 146 to 214 days a year at 32°F or colder, so the route a new line takes matters as much as its material. We favor heated space and keep lines off garage, crawl-space and exterior walls wherever the house allows.
PEX or copper
PEX is sold in coils, flexes around framing and takes fewer joints, which helps in finished walls. Copper is rigid and has decades behind it. Either way the new lines go through hand-sized holes in the drywall, which are closed after a pressure test.
Prefer to start from the symptom? Our leak detection and slab leaks page covers hidden water, a first sign of failing pipe, and the home page lists every other service.