Where Is Your Main Water Shutoff, And Do You Know How To Use It?

When a pipe bursts, a water heater splits, or a supply line under a sink lets go, the size of the damage depends on one thing more than any other: how long it takes someone to close the main water shutoff. A household water line can put several gallons a minute onto a floor, and that water keeps coming until somebody turns the valve.

Most people have never touched theirs, and plenty do not know where it is. This guide covers where the main shutoff usually sits in Denver area homes, how to close it, what to do in the first few minutes after, and how to make sure it actually works before you need it.

Why Knowing Where It Is Matters

Water damage is mostly a function of time. A slow drip from a failed fitting can be cleaned up with a towel. A split line running unattended for twenty minutes can soak a finished basement, wick up into drywall, and get into flooring and insulation. The pipe repair is usually the smallest part of the job. The cleanup, drying, and rebuilding are the large part, and every minute the water runs makes them larger.

The situations where you need the main in a hurry are common:

• A burst or split pipe, often after a hard freeze or when a frozen line thaws.
• A failed water heater leaking from the tank itself.
• A broken supply line to a toilet, faucet, washing machine, or refrigerator.
• A leak you cannot isolate, such as water coming through a ceiling with no obvious source.
• Planned work, such as replacing a fixture or a valve that has no shutoff of its own.

In every one of these, closing the main first and figuring out the cause second is the right order.

Where To Find It In A Denver Area Home

The main shutoff is almost always close to where the water service line enters the building. Find that point and you have usually found the valve.

Homes with basements

Look on the basement wall that faces the street, low on the wall or near the floor. In many older Denver homes the water meter is inside, and the main shutoff sits right next to it, often with a second valve on the other side of the meter. Check behind storage shelves, inside furnace closets, and behind access panels. In a finished basement, a valve hidden behind a small drywall panel is common.

Crawl spaces

In a home with a crawl space, the valve may be just inside the crawl space access, near the foundation wall on the street side. Some builders also added a second shutoff in an easier spot upstairs, often near the water heater, so check there too.

Slab homes, townhomes, and condos

Homes built on a slab often have the main shutoff in the garage, in a utility or water heater closet, or on an interior wall near where the line comes up through the floor. In townhomes and condos, your unit may have its own shutoff inside, often near the water heater or under the kitchen sink, while the shutoff for the building sits in a shared mechanical room. Ask your association where both are before you need them.

Outside the house

Some homes, particularly newer ones, have the water meter outside in a meter pit near the sidewalk or property line, under a round metal or plastic lid. There is also a curb stop, a valve on the service line near the street inside a small round box with a cap. These valves are operated with special keys and are normally handled by the water utility. Denver Water treats the service line and meter pit as the property owner's responsibility, including keeping them accessible. If the leak is between the street and the house, call the emergency number for your water utility, listed on your bill, to have the curb stop closed.

Still cannot find it? Follow the cold water line backward from the water heater, or look for the pipe coming through the foundation wall. A pressure reducing valve, a bell shaped brass fitting, often sits just past the main. While you are there, look at the pipe itself. Our guide to polybutylene and galvanized pipes explains what to watch for at the meter.

What The Valve Looks Like

Most Denver area homes have one of two types.

• Gate valve. A round handle, sometimes called a wheel handle, on a brass body. It takes several full turns to close. Gate valves are common in older homes, and they are the type most likely to seize, leak at the stem, or fail to shut off completely after years without use.
• Ball valve. A straight lever handle that closes with a quarter turn. When the lever runs in line with the pipe, the valve is open. When it sits across the pipe, the valve is closed. Ball valves are more reliable and are the standard choice when a main shutoff is replaced.

You may also find a valve on each side of the water meter, a pressure reducing valve just past the main, and a separate valve for the irrigation system. Label the main clearly so nobody has to guess which one it is during an emergency.

How To Close It

1. Clear the path. Move anything stored in front of the valve so you can reach it quickly.
2. Turn it the right way. For a round handle, turn clockwise until it stops. For a lever, turn it a quarter turn until it sits across the pipe.
3. Do not force it. If a gate valve will not turn with firm hand pressure, stop. A wrench or a length of pipe for leverage can snap an old valve stem, and a broken stem can turn a leak into a flood at the valve itself. If the main will not close, call your water utility to close the curb stop, and call a plumber.
4. Confirm the water is off. Open a faucet on the lowest level of the house. Flow should slow to a trickle and stop as the lines drain.
5. Take care of the water heater if the shutdown will be long. A tank water heater stays full when the main is closed, so a short shutdown is fine. If the water will be off for hours, or you will drain the lines, set a gas water heater to vacation or pilot and switch an electric water heater off at the breaker. An electric element that heats without water around it fails quickly.

Turning The Water Back On

Once the repair is done, open the main slowly. Turning it back on all at once sends a surge of pressure and air through the lines, which can knock loose sediment and stress old fittings.

1. Close the faucets you opened, except one on the top floor and one on the lowest level.
2. Open the main about a quarter of the way and listen as the lines refill.
3. Open it fully once the sound of rushing water slows.
4. Let the open faucets run until water flows steadily without sputtering, then close them. Run each of the other faucets briefly to clear the air.
5. Restore the water heater once water runs from the hot side, then set the gas control back to on or switch the breaker back on.
6. Check the valve stem. A gate valve that has not moved in years sometimes starts to drip at the stem after it is turned. Gently snugging the packing nut just below the handle often stops it. If it keeps dripping, have the valve replaced.

Test It Once A Year

A shutoff valve that never moves tends to stop moving. Minerals build up inside it, and on a gate valve the packing around the stem dries out. Once a year, close the main fully, confirm the water stops at a faucet, and open it again slowly. Fall is a good time, alongside the rest of the freeze prevention checklist.

Replace the valve if you notice any of these:

• It will not turn, or it turns but the water does not stop.
• It leaks at the stem or the body.
• It is heavily corroded or crusted with green or white mineral buildup.
• It is an old gate valve you no longer trust in an emergency.

Replacing a main shutoff usually means stopping the water ahead of the valve, which can involve the utility closing the curb stop. A licensed plumber will typically install a full port ball valve, which closes with a quarter turn and holds up far better over time than an old gate valve.

The Other Shutoffs In Your House

The main shuts off everything. For a leak at a single fixture, a local shutoff lets you stop the water there and keep the rest of the house running.

• Under sinks and behind toilets. Small valves on the supply lines, often called angle stops. Turn them clockwise to close. Older ones seize just like a main, so test them when you test the main.
• At the water heater. A valve on the cold water line entering the top of the tank shuts off water to the heater only.
• At the washing machine. Two valves, hot and cold, usually in a box on the wall behind the washer. Rubber washer hoses are a common failure, which makes these valves worth knowing.
• For hose bibs and irrigation. Many homes have separate interior shutoffs for the outdoor faucets and a separate valve for the sprinkler system, both of which get closed in the fall.

Automatic Shutoff Valves

An automatic shutoff valve is installed on the main line and closes itself when it detects a leak, either through sensors placed near water heaters and under sinks or by watching for water flow that does not stop. They are worth considering for homes that sit empty during travel, homes with finished basements, and anyone who has already had a water loss. They do not replace knowing where the manual valve is, since a power outage, a dead battery, or a failed sensor can leave one unable to act. Ask a plumber whether one fits your system.

What To Do After You Close It

With the water stopped, the urgent part is over. Next steps:

1. Turn off power to wet areas if water has reached outlets, fixtures, or appliances, and stay out of standing water near anything electrical.
2. Move belongings out of the water and start removing what is standing.
3. Take photos of the damage and the failed part before anything is cleaned up, for your records and for any insurance claim.
4. Find the source. If it is obvious, a plumber can repair it. If water appeared with no visible cause, leak detection locates it without opening more walls than necessary.

Finding your main shutoff takes about five minutes. Do it this week, test it, label it, and show everyone in the house. If it will not turn, leaks, or cannot be found, our licensed plumbers can locate, test, and replace a main water shutoff anywhere in Denver Metro.