What should I do while waiting for the plumber?

Close the valve nearest the problem first. Almost every fixture has its own stop valve: a small oval or football-shaped handle on the supply line under a sink, behind a toilet, or near an appliance. Turn it clockwise until it stops. That isolates one fixture and leaves the rest of the house with water.

When the leak is bigger than one fixture, such as a burst supply line, a slab leak, or water you cannot trace, go to the main water shutoff instead. In most Phoenix homes the main valve sits near the front hose bib, in a garage, or at the meter box by the street. Turn it clockwise (a lever style turns a quarter turn until it is crosswise to the pipe). This stops all water entering the home. See our guide on finding your main water shutoff if you have never located yours, and ideally tag it before an emergency so you are not hunting for it during one.

If a valve is stuck or spins without stopping the flow, do not force it until it breaks. Move to the next valve upstream, the main shutoff, and tell the plumber which valves are bad when they arrive. Old shutoff valves seize up in Phoenix because hard-water scale builds on the stem, so a valve that has not been turned in years may resist. A gentle, steady turn works better than a hard yank. If even the main valve will not close, the curb valve at the meter is the last stop, though that one usually needs a meter key and is the water company's territory.

A water heater holds 40 to 50 gallons and stays under pressure, so the shutoff order matters. Take these steps:

1. 1Cut the energy first. For an electric unit, switch off its dedicated breaker in the panel. For a gas unit, turn the gas control knob to "Off" or close the gas shutoff on the supply line. Doing this first stops the burner or element from firing on a tank that may be draining.
2. 2Close the cold-water inlet. A valve sits on the cold line entering the top of the tank, usually marked or on the right. Turn it clockwise to stop water feeding the tank.
3. 3Drain the lines to relieve pressure. Open a low faucet, such as a tub spout or an outdoor hose bib on the lowest level, so the remaining water in the pipes runs out there instead of through the leak. Opening a hot tap also breaks the vacuum so the tank drains more cleanly if the plumber needs it emptied.

If water is pooling near the unit, keep it away from the burner area and any nearby outlets. Do not touch electrical parts while standing in water. A tank leaking from the bottom seam is almost always failed past repair and will need replacement, so there is no fix to attempt yourself. Your job before the plumber gets there is simply to stop the water and energy and keep the area dry. If the tank sits in an attic or a closet with a drain pan, check that the pan line is carrying water away and not overflowing onto the ceiling below.

Once the water is off, shift to containment and safety. The goal is to keep water away from people, electronics, and anything it can ruin.

• Contain the water. Lay down towels, slide a bucket or shallow bin under an active drip, and use a wet/dry vacuum or mop on standing water. Pull back rugs and open interior doors so air moves and floors dry.
• Move valuables and electronics. Lift electronics, power strips, important papers, and anything fabric or wood off wet floors. If water is near outlets or a panel and you can reach the breaker safely and stay dry, cut power to that area.
• Document everything for insurance. Take clear photos and video of the source, the standing water, and every damaged item before you clean up. Ready.gov advises homeowners to "take photos or videos of the damage" for insurance claims and to contact your insurer promptly. This record protects your claim later.

For a sewage backup, treat it as a biohazard. Keep people and pets out of the affected area, do not walk through it, and avoid using any other drains, toilets, or the washing machine in the house so you do not add to the backup. Wastewater carries bacteria, so wait for the professional and wear gloves if you must move anything nearby. Open a window for ventilation, but do not run fans that blow across the contaminated water and into living spaces. If the backup is coming up through a floor drain or a lower shower, that points to a main-line problem, which is one more reason to stop sending water down any drain until the plumber clears it.

If you ever smell gas (a rotten-egg or sulfur odor) or hear a hissing near a gas line or water heater, stop and treat it as a true emergency. Leave the building right away, do not flip switches, light a flame, or use a phone or garage door opener inside, and from a safe place outside call 911 and your gas utility. The American Red Cross puts it plainly: "If you detect natural or propane gas, or hear a hissing noise, leave the property immediately and call the fire department after you reach safety." In the Phoenix area, Southwest Gas runs a 24-hour emergency line at 877-860-6020 and tells customers to leave the area at once and call from a safe location, day or night. Do not wait inside for the plumber when gas is in the air.

A few common reactions make the problem worse. Skip these:

• Do not pour chemical drain cleaner down a clogged or backed-up drain. It rarely clears a real blockage, it can sit in standing water and splash, and it creates a chemical hazard the plumber then has to work around. Our page on whether Drano is bad for pipes explains why these products can damage pipes and harm the people handling them. Use a plunger or wait for the pro instead.
• Do not keep running water through a fixture that is leaking, overflowing, or backing up. Every flush of a clogged toilet or run of a leaking faucet adds to the flood. Shut the local stop valve and leave it off.
• Do not ignore a small active leak because it seems minor. The EPA reports the average household's leaks waste nearly 10,000 gallons of water a year, and a single home can leak more than 50 gallons a day. A drip you leave running for hours is both wasted water and creeping damage, so contain it now.
• Do not use electrical appliances or outlets near standing water, and do not enter a flooded basement or low area if water has reached wiring or the panel.

Some situations need the water off and a call placed before anything else: a burst pipe, flooding you cannot stop at a stop valve, a sewage backup, no water at all, or any gas smell. These are the calls where the steps above buy you time and limit the loss. Our guide on when to call an emergency plumber breaks down which problems justify a 2 a.m. visit and which can hold until morning.

For slower issues, a single dripping faucet, one slow drain, a toilet that runs now and then, you can usually wait for a scheduled appointment. Still, do not let them sit for weeks. The EPA urges homeowners to fix leaks promptly as part of routine home maintenance, and it endorses leak-detection and automatic shutoff devices that catch a problem and stop the water before you are home to notice. A smart leak sensor near a water heater or under a sink can shut the supply on its own, which is worth considering after any scare like this one.

It also helps to clear a path before the plumber arrives. Move boxes, parked cars, or stored items away from the shutoff, the water heater, or the affected fixture so the technician can get straight to work. Have your address and a short description of the problem ready when you call, and keep your phone nearby in case they need directions to a gate or a meter.

When the plumber arrives, point them to the shutoff you used, describe what happened and when, and show them your photos. That hands them a clear picture and a dry work area, which is the fastest path to a real fix.