In a plumbing emergency—whether it’s a burst pipe, a broken water heater, or after an earthquake—every second counts. The single most important thing you can do to minimize damage is to stop the flow of water immediately. That means every person in your home needs to know where the main water shut-off valve is and how to use it. It’s not complicated, but it’s absolutely essential.

First, you have to find it. In most San Francisco homes, the main shut-off valve is located where the city’s water line enters your property. Common spots include: in the garage, near the water heater, in a basement or crawlspace, or in a utility box near the street side of your house. It’s usually a brass or plastic valve on a large pipe. Look for a round wheel (called a gate valve) or a lever (called a ball valve). If you live in an apartment or condo, your individual unit’s shut-off might be under your kitchen sink or in a bathroom vanity. If you can’t find it, ask your landlord or building manager now—don’t wait for an emergency.

Once you’ve found it, know how to turn it. For a gate valve (a round wheel), turn it clockwise (to the right) until it is completely tight. Do not force it; if it’s stuck, a little penetrating lubricant can help. For a ball valve (a lever), it should be perpendicular to the pipe to be OFF. If the lever is in line with the pipe, the water is ON.

Here’s the action plan: The moment you see a major leak, yell for someone to run and turn this valve off first. Don’t try to grab towels or find a bucket first—stop the water at its source. Then, you can call for help. At Starboy Plumbing, we offer 24/7 emergency service for exactly these moments. We can talk you through finding the valve if you’re unsure, and we’ll be on our way fast to make the permanent repair. Taking five minutes today to find and label this valve is the best free insurance policy you can have for your home.