A water pipe comes up from my hot water heater to a T-fitting. On the left side of the "T," the pipe extends to various fixtures through the rest of the house. To the right side of the "T" is a shut-off valve from which a copper pipe extends and winds to another part of the basement, where it's capped off (no other valves, etc. to that point).
Is there a purpose for this? I haven't seen anything like this in a plumbing diagram/plan. Most seem to have a pipe extending from the hot water heater alone to the rest of the house.