Close the building's main shut-off valve, not the utility's meter. Then call the water utility if the break is on its side of the meter, or a plumber if it is on yours. Warn tenants, start drying within 24 to 48 hours, photograph everything for the insurer, and flush lines when water returns.
Step 1: Stop the water at the right valve
Close the building's main shut-off valve. The City of Phoenix Water Services Department tells customers to turn off the water "at the main shut-off valve," and it says it is "important for you to NOT shut your water off at the meter." The meter needs a special tool, and the city says you may be held responsible for a damaged meter. If nobody can find or work the building valve, the city says its customer service office will send a technician to shut the water off at the meter.
Know this valve before you need it. Put its location in the building's emergency binder, and see how to plan a commercial water shutoff.
Step 2: Work out who owns the break
Phoenix draws the line at the water meter. Its Water Services Department is responsible for repairing leaks, broken pipes and water mains "on the city, or street side of the water meters," and breaks on private property are the property owner's responsibility. If the leak is on the street side, call the city's emergency number, 602-261-8000. If it is on your side, you need a plumber now. Other cities and water companies draw the line in their own places, so check your utility's rules.
Step 3: Tell tenants what is happening
Post a notice on every door and in the lobby: water is off, where the break is, when you will update them, and who to call. Ask residents to keep taps and washing machines off until the line is repaired.
Step 4: Start drying within a day or two
The EPA's mold guidance says: "In most cases, mold will not grow if wet or damp items are dried within 24-48 hours." So pull wet carpet and pad, extract standing water and get fans and dehumidifiers running early. Don't wait for the adjuster to show up before you start. For the first-hour safety steps around water and electricity, see what to do after a major water leak.
Step 5: Document for insurance
Triple-I, the insurance industry's information group, lists these steps for a business claim: contact your insurer as soon as possible, "take reasonable steps to protect your property from further damage," and save receipts, because payments for temporary repairs are part of the total settlement. It also suggests photos or video of the damage and an inventory of what was lost. Keep a log of who you called and when. More in how to file a water damage insurance claim.
Step 6: Flush the lines after the repair
A break can let outside water into pipes. The Iowa Department of Natural Resources, writing for water utilities, says a loss of pressure "may allow disease-causing microorganisms from surrounding soil or groundwater to enter a distribution system pipe." The EPA notes that when pressure in the public system drops below the pressure in the connected plumbing, backflow contamination can occur.
If the utility issues a notice, follow it; see what to do during a boil water notice. Iowa's guidance also says customers should flush their internal plumbing after repairs, should not use colored water for drinking or cooking, and should keep flushing until the water is clear. That is guidance for Iowa utilities, so follow your own utility's instructions where they differ.
Where HQ fits
If the break is on your side of the meter, HQ handles emergency commercial plumbing 24/7. We are licensed and insured, and you get upfront pricing and a free estimate before repair work starts. Ahead of time, our after-hours plumber checklist tells you what to have ready when you call.