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Locating and Operating Your Main Water Shut-Off Valve

Knowing where your home's main water supply is located, and how to turn it off, is as important as knowing how to find and reset an electric circuit-breaker.

Every home was required to have a main water shut-off valve installed inside the home when it was built. For most emergencies or repairs, shutting off the proper inside valve is all you will need to do. However, there are also underground shut-off valves installed outside at the property line. If it's necessary to shut off this valve, please call a registered master plumber or WSSC Water at 301-206-4003 to work this valve.

Where are my supply valves? 

It is important to understand that different plumbing arrangements will dictate where the proper main supply valve is located. Some homes have the water meter located inside, while others are located outside, underground within a “pit” at or near the property line or right-of-way. Some homes also have submeters, which typically are inside even if the main meter is outside/underground. Newer homes have fire sprinkler systems, while older ones generally do not. Home construction also differs greatly; basements, crawl-spaces, and slab-on-grade. Water shut-off valves may have round “wheel” handles or lever handles.

Locating the proper valve

Basements – the shut-off valve is typically located near the front foundation wall. The main water may come through the concrete floor or through the wall. The valve is typically within three to five feet of where the main water enters. In some cases, the main water may enter in a different area, like a mechanical room, up through the floor, near the water heater or furnace.

Crawl-space plus a basement – the shut-off valve may be where the water enters the basement; in some older homes, the shut-off may be inside the crawl space. If your shut-off valve is located in a crawl space, you may want to consider a secondary valve located in the basement.

Crawl-space with no basement – the shut-off valve typically is located near the water heater or under the kitchen sink, but anywhere is possible. If it is located inside the crawl space, you may want to consider a second valve located in the living space, for example, near the water heater or under a sink.

Slab-on-grade construction – the shut-off valve typically is located near the water heater or under the kitchen sink, but anywhere is possible.

Which valve should you operate?

If your home has a fire sprinkler system, care is needed when selecting a shut-off valve. Unless it is a sprinkler pipe that is leaking, you should only shut off the plumbing supply and leave the sprinkler piping charged/live.

If the water shut-down is for a broken sprinkler line or sprinkler head, locate the first valve (that is, the one closest to the main water line entry point) and operate that valve as described below.

For all other general plumbing shut-offs, emergency and non-emergency:

  1. For homes with fire sprinklers and an inside main water meter, locate and operate the second valve (it will be above the main meter and past (downstream of) the fire sprinkler system “tee”). If you have a submeter, its second valve will only isolate the irrigation and/or hose bibbs.
  2. For homes with fire sprinklers and an outside main water meter, locate and operate the second valve, it will be past (downstream of) the fire sprinkler “tee.”
  3. For homes without fire sprinklers and with an inside main water meter, either valve will shut off supply to the home, but operating the second valve is a good practice and a safeguard if you are not sure if your home has fire sprinklers.
  4. For homes without fire sprinklers and with an outside main water meter, you likely have only one shut-off valve that will shut down the entire home.

How to close the main valve (Shut-off/Turn-off)

  1. Round “wheel” handle valves will turn off by turning the handle clockwise. It may take two or more full revolutions.
  2. Slowly turn level handle valves ¼ turn, until the handle is not parallel with the pipe. It should stop at a ¼ turn.
  3. Open a tub or sink faucet (hot and cold) on the highest level of the home to relieve pressure, and watch that spout to ensure that water has stopped flowing. Then continue to open faucets throughout the home to drain-down as needed.
  4. If draining down the home, be sure to de-energize the water heater and boiler where applicable by shutting off power to electric water heaters and any type of boiler. For gas water heaters, turn thermostat down to the pilot-only setting; if you drain the heater, turn off the gas.

Opening the main valve (Open/Turn-on)

  1. Close all faucets except a tub or sink on the highest level of the home.
  2. Partially turn on valves slowly; extra slow for lever handles; stop after ½ revolution on wheel handle, ½ of a ¼ turn for lever handle; with water flowing, slowly turn off highest open faucet.
  3. Listen for water pressure to equalize (noise ends); fully open main valve. Bleed air from lines by slowly opening (hot and cold) on all faucets, one at a time, until air stops flowing, then close each faucet; repeat the process on all faucets until complete.
  4. Turn power on to electric water heaters and boilers only after the water system is full and all air has been bled out. If gas was turned off, carefully follow re-starting directions on the appliance jacket or call a registered plumber or your gas company for service.

 

Last Modified: December 23, 2020, 1:31 pm EST