PEX pipes withstand both hot and cold temperatures.
How can you tell which water line is hot and cold under the sink?
Identify the cold-water line under the sink. If you aren't sure which line supplies the cold water, try turning on the hot water. Allow the water to heat up, and then feel the pipes under the sink. The pipe that isn't hot is the cold-water supply.
How do you tell which water lines are hot and cold?
Plumbing for a kitchen sink includes a drain line, a pair of water lines, and a couple of valves. The hot water is on the left side while the cold water is on the right.