Due to serious lack of appropriately placed shut-off valves in my house plumbing (not my fault, it came that way), I need to shut off the cold water supply to my gas hot water heater so I can replace a bathroom faucet.

Long story short, there are no shut off valves to the faucet in question, nor are there shut off valves further back along the hot or cold water supply. So I think my best option is to shut off the whole house supply, then run both hot and cold lines until they are empty, perform the faucet change, and be on my way.

My concern is the hot water heater. I'm reading conflicting things on the Internet, and can't find a direct answer to this question: Is it OK to drain the hot water tank for a short time via the house lines (hopefully less than an hour, and not a true, full-on draining of the tank) without risking serious damage to the heater and its components? And if it is, do I fully shut the hot water heater off, or can I just put it in pilot mode? My thinking with the pilot mode approach is that I'm not truly draining the tank, just running the faucet to drain the outgoing line.

  • 1
    Pilot mode will be fine for an hour. Unless this is the lowest level faucet in the house you also don’t need to drain the whole system. Just enough that water doesn’t come out where you need to work.
    – Tyson
    Sep 24, 2018 at 14:51

1 Answer 1


If you turn the supply of water to the water heater off you don't need to drain it , with the supply off you do want to turn the gas valve to pilot or off depending on the type of tank some have electric ignightors and don't have a standing pilot. The tank will be fine. After that I open the lowest taps in the home usually a bathtub if single level then the taps you want to change and the water in the pipes drain down to this level, a hose bib outside many times is at the lowest position for cold water. Now that you have the lines open would be a great time to add shutoffs to this fixture when installing the new faucet.

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