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Home water and gas systems contain two types of shutoff valves: main or master shutoff valves for stopping the flow of gas or water to the entire house, and individual or supply shutoff valves for specific appliances and fixtures. We’ll look at both types and tell you how to identify them (since they often look similar), where they are and how to operate them.
You’ll notice this story contains a lot of “oftens,” “usuallys” and “almost always’s.” That’s because valves vary greatly in location, shape and number, depending on the age of your house, the local codes and which part of the country you live in.
Here are the basics of each system.
Gas Shutoff Valves
Houses with natural gas have a main shutoff valve (Fig. A)
located just before the gas meter. This valve, often called the street-side
valve, is normally a rectangular nub (Photo 1). When the long side of the nub
or handle is parallel to the incoming gas line, it’s open and the gas is
flowing. When it’s turned a quarter turn, perpendicular to the incoming
pipe, it’s closed.
The street-side main shutoff valve must be opened and closed with a wrench, and, truth be told, gas companies don’t want you operating this valve; they only want their own employees, plumbing and heating contractors and fire department personnel to use it. They’d rather you use the house-side main shutoff valve located after the meter (Photo 2). This house-side valve—usually a ball valve—may be located where the pipe first enters the house or farther down the line, but it will always be located before the first appliance. If iron pipe is transporting the gas, it’s often black; this differentiates it from similar-shaped, gray galvanized water pipe.
FIG. A: Typical Gas System
Click image to enlarge.
Well, don’t just sit there; get up and locate those valves! Then tag ’em as we explain in Fig. B.
In addition to the house-side main shutoff valve, individual gas appliances should have a service or appliance shutoff valve (Fig. A) that’s immediately accessible, in the same room and within 6 ft. of the appliance. These valves allow you to stop the flow of gas to your dryer, oven, furnace, water heater or gas fireplaces to make repairs or new installations without cutting off gas to your entire home. Most service valves are single-lever ball valves; again, handle parallel to the line means gas is flowing, perpendicular means it’s cut off. On dryers and ranges, this valve is usually hidden behind them and can only be reached by sliding the appliance out from the wall. This service valve will usually be at the end of a fixed pipe and connected to a flexible supply pipe called an appliance connector. Take care not to kink or pinch this flexible pipe. When you repair or replace a gas appliance, use these shutoff valves to stop the flow of gas. (Most pros replace the flexible connector when they replace the appliance.) If you discover you have a faulty supply valve, or your system doesn’t have one, turn off the gas using the houseside main shutoff valve.
For those with propane or liquefied petroleum gas, there’s a main shutoff valve on the tank itself, and usually a main shutoff valve somewhere before the first appliance.
Some valves (both gas and water) manufactured before 1980 contain a lubricant to help the valve seal better and operate more smoothly. In many cases, this lubricant will have hardened or reacted with the gas to make the valve difficult to turn. Applying gentle heat with a hair dryer and working the valve open and shut in stages will usually free it up again. Sometimes you need to use a pliers to free the stuck handle.
Important! Now that you know where your gas valves are, also know this: it’s not always safe for you to turn these valves off in an emergency. When gas reaches a certain concentration in a room or house, the slightest spark can set off a tremendous explosion. A light switch or telephone—even static electricity from your clothes—can produce such a spark. If you’re working near the main or individual gas valve and clearly know the source of the gas leak and that gas hasn’t been leaking for long, shut off the valve and get out. But if you’re uncertain of the source or how long the gas has been leaking, clear yourself and your family out and call the gas company or fire department from a neighbor’s house (not your own—remember, phones can generate sparks!). Always err on the side of caution.
Shutoff Tag
FIG. B
Click image to enlarge.
FIG. C: Typical Warm-Weather Water System
Click image to enlarge.
Also note: When you shut off main or individual gas valves, you’ll be extinguishing the pilot lights to certain appliances. Many newer appliances have “pilot light–less” electronic ignition systems, but if you have older appliances, you’ll need to relight the pilot lights. Most appliances have clear relighting directions on a label near the pilot light or in the instruction manual. But some pilots are pretty darn hard to reach. If you’re uncomfortable with relighting the pilot light, hire a plumber or call your local gas service company.
Water Shutoff Valves
Almost all water meters have one main shutoff valve
directly before the meter and another directly after (Photo 5). Where the meter is located depends on
the climate in your area.
In cold climates (Fig. D), the meter and main shutoff valves are located inside, usually in a basement or other warm area to prevent freezing. In milder climates (Fig. C), the meter and its two shutoff valves may be attached to an exterior wall or nestled in an underground box with a removable lid. Between the water main in the street and the meter, there’s also usually a buried curb stop valve (accessible only by city workers wielding special long-handled wrenches) and a corporation stop, where your house water line hooks up to the water main. Your city absolutely doesn’t want you messing around with these last two valves. They prefer you turn your water off or on using the main valve on the house side of the meter. This valve will normally be a gate-type valve, with a round knurled handle, requiring several full clockwise rotations to turn off. In newer homes, it could be a ball valve.
In addition, most houses built today have small, localized shutoff valves called fixture supply stops (Photo 6) installed on the supply lines leading to toilets, faucets, dishwashers, washing machines, water softeners and water heaters. These supply stops usually have a small round or oval handle that you turn clockwise two to four full turns to shut off the flow of water. Many older homes have them only at toilets if at all. This can lead to great family discord, since working on a single drippy faucet can require shutting off water to the entire house at the main valve, leaving everyone showerless, flushless and waterless. With supply valves, you can turn off the water to a single fixture while fixing or replacing that faucet. If your plumbing system lacks supply stops, install them when you shut off the main valve to repair a sink, toilet or appliance. Eventually you’ll have supply stops at every fixture, and your family won’t yell at you every time they see you with a wrench in your hand. Remember, fixture supply stops must be easily accessible; you can’t drywall or plaster over them without installing an access panel to reach them.
Supply Stop Problems
Be aware of these common problems with fixture supply
stops:
Many water supply valves drip when turned off and then back on again after an extended period of disuse. To fix a drippy supply valve, try gently tightening the packing nut (Photo 6) with a wrench, or opening and shutting the valve several times until the drip stops. If a supply valve simply won’t stop leaking, your only option is to replace it—which will require shutting off the main valve.
In cold climates, most people remember to close the supply shutoffs for their outdoor spigots to prevent freezing, but many then forget to open the outside spigot to drain the remaining water. If the water trapped between the spigot and supply shutoff valve freezes, it can burst that section of pipe. Since there’s no water flowing through this short damaged section of pipe, there are no obvious leaks or sign of damage—yet. But when you turn the supply valve back on in the spring and pressure returns to that pipe, the burst section of pipe will leak like crazy—and often go unnoticed for hours or days. One plumber told me he’s made dozens of repairs dealing with this mistake.
FIG. D: Typical Cold-Weather Water
System
Click image to enlarge.
Finally, many icemakers and furnace humidifiers are fed by small flexible copper tubes that are connected to larger copper pipes via a very small T-handled device called a saddle valve (Photo 4). These valves essentially bite into the larger pipe to feed the smaller one. Leaky saddle valves are a major cause of residential water damage and are no longer code-compliant in many areas. If you have saddle valves, replace them with standard supply stops.
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