Every emergency article ever written tells you to shut the water off. Almost none of them tell you where the valve is, and 2am with water coming through a ceiling is a bad time to start looking.
This takes twenty minutes on a Saturday and it is the highest-value twenty minutes of home maintenance there is. Do it once, write it down, show everyone in the house.
1. The main water shutoff
This is the important one. It stops all water entering the house.
Where to look: where the water line comes in, which is almost always a basement or crawlspace wall on the street-facing side of the house. In a slab house, look in a utility closet, the garage, or near the water heater. In a townhouse or condo, it may be in a utility closet with the water heater, and in some buildings there is no unit shutoff at all, which you genuinely need to know in advance.
What it looks like: either a round wheel handle or a lever. A lever is a quarter-turn ball valve: perpendicular to the pipe is closed. A wheel turns clockwise to close, and may need several turns.
Now actually turn it. This is the step people skip. Close it, go upstairs, open a tap and confirm the water stops. Then open the valve again, fully. A valve that has sat untouched for twenty years frequently will not budge, or will not seal, or will start weeping from the packing nut once it moves. Finding that out on a Saturday is a scheduled repair. Finding it out during a burst pipe is a flooded floor.
If it is seized, do not force it with a wrench until it snaps. Have it replaced. The price depends entirely on where it sits and what is around it, which is why we look before quoting that one.
2. The meter valve, and who owns what
Outside, usually in a pit near the street under a cast iron lid, is the meter and a utility valve. Fairfax Water and Loudoun Water both draw the line the same way: the meter is theirs, and everything from the meter to your fixtures, including the buried service line across your yard, is yours.
That outside valve is the utility’s and generally not yours to operate. It matters for a different reason: if your main shutoff inside fails and water will not stop, that pit is what the utility will use, so knowing where it is speeds up the call.
While you are there, learn to read the meter. Everything off in the house for fifteen minutes, then check whether the little triangle or star is turning. That is the leak test you will use later. The rest of the method is here.
3. The gas shutoff
Two places, and the distinction matters.
At each appliance. A small valve on the line feeding the furnace, water heater, range or dryer. Handle in line with the pipe is open, across it is closed. This is the one you use if a single appliance has a problem.
At the meter. There is a main valve on the gas meter outside, usually needing a wrench to turn a quarter turn. You should not normally be the one turning it. If you smell gas, the instruction from Washington Gas is to leave the building without touching light switches or appliances, leave the doors open behind you, and call them at 844-927-4427 or 911 from somewhere safe. They come free, any hour, and they will shut it off. Do not go looking for the leak.
Once gas is shut off at the meter, relighting appliances is the utility’s job, not a homeowner’s.
4. Individual fixture shutoffs
Under every sink and behind every toilet there is a small valve, usually called an angle stop. These let you isolate one fixture without shutting down the house, which is what you want for a running toilet or a leaking faucet.
They also fail. They are cheap chrome valves that sit untouched for decades and then seize or weep the first time they are turned. If you find one that will not move, that is worth replacing on your schedule, especially in a bathroom over finished space.
The braided supply lines connecting those valves to the fixture have a service life too, and a failed one sprays at full pressure until somebody finds the main. Replacing them preventively is inexpensive.
5. The water heater
There is a shutoff on the cold water line into the heater. Knowing it exists means you can isolate a leaking water heater without killing water to the whole house.
Also find, on a gas unit, the gas valve at the heater, and on an electric unit, its breaker. A leaking tank should have both the water and the energy source shut off. How to tell a fitting leak from a failed tank is here.
6. The electrical panel, and the two HVAC breakers
Find the panel and make sure the labels are accurate, because in most houses they are not. Two in particular are worth labelling correctly: the indoor air handler or furnace, and the outdoor unit if you have a heat pump or air conditioner. Many systems also have a separate breaker for electric heat strips, which is the one people never know about until a winter goes by cold.
There is also a switch that looks like a light switch on or near the furnace. That is the furnace service switch, and it gets flipped off by accident more often than you would think.
Outside, near the condenser, is a grey box called the disconnect. It gets pulled during yard work and painting and then forgotten.
7. The sump pump and the outdoor spigots
If you have a sump pump, know which outlet it is plugged into and which breaker feeds it, and test it with a bucket of water twice a year.
And if your outdoor spigots have interior shutoff valves, usually in the basement near where the pipe leaves the house, find those now, because closing them in November is the single best defence against the most commonly burst pipe in this region. That story is here.
Write it down
Make one note, on paper, taped inside a cabinet door or on the panel, and a photo of it in your phone. Main water shutoff and how it turns. Gas shutoff and the utility’s number. Water heater shutoff. Furnace switch and its breaker. Outdoor disconnect. Sump pump breaker. Which outdoor spigots have interior valves.
Then show whoever else lives there. The person who knows where the valve is not being home is how a small leak becomes a claim.
While you are checking
Put a $12 gauge on a hose bib and read the static pressure. Code requires a pressure reducing valve where it exceeds 80 psi, and parts of this region come off the main well over 100. Those valves wear out in ten to fifteen years, and a failed one stresses every fitting, fixture and appliance in the house. Replacing one runs $500 to $994. It is the repair that quietly prevents the next three.
SwiftPro handles plumbing, heating and cooling across Northern Virginia. Call (703) 997-9757 or book online. If water is coming in right now, shut the main and call the 24 hour line.
