Shutting Off Water and the Water Heater for a Slab Leak

The valves that matter

House main shutoff: Usually where the supply enters the home, often near a front hose bib or in the garage
Water heater cold inlet: On the cold pipe going into the top of the heater; closing it stops hot side flow
Fixture stops: Small valves under sinks and behind toilets for single fixtures
Meter valve: In the meter box; belongs to the water provider and is a last resort

Which valve to close

IfWater is pooling or flooring is soakingThenClose the house main right away.
IfThe leak is confirmed on the hot side and is slowThenClose the water heater's cold inlet and use cold water only.
IfThe leak is on a cold line and slowThenClose the house main overnight and whenever the house is empty.
IfThe house main will not close or is brokenThenContact your water provider about the meter valve, and tell the plumber the main needs attention.

Closing the house main

Find it before an emergency.Walk the front of the house and the garage for a valve on the incoming line. Some homes have a lever handle, others a round wheel.
Turn it fully.A lever turns a quarter turn so the handle crosses the pipe. A wheel turns clockwise until it stops.
Check.Open a faucet inside. Flow should slow to nothing within a minute.
Do not force it.If the valve is stiff or seized, forcing it can break it. Stop and call for help.

Living with the water off

With a hot line leak, many households get by for a few days with cold water only: cold showers are unpleasant but manageable, and dishes can be washed with water heated on the stove. With a cold line leak, opening the main for short periods to fill pots and flush toilets is a common approach until the repair.

Keep an eye on the meter each time you open the main. If the leak seems to be speeding up, or damp areas are spreading, move the repair up and keep the water off more of the time.

Shutoff readiness checklist

Locate and label the house main shutoff.
Make sure the water heater cold inlet turns freely.
Know where the meter box is and how to read it.
Keep a flashlight near the main shutoff.
Tell everyone in the household where the main is and how to close it.
Ask a plumber to replace any shutoff that is seized or leaks at the stem.

Common questions

Is it OK to leave the water heater without water?

A full tank sitting unused is fine as long as it is not heating. Turn it to vacation or off while the inlet is closed, and follow the manufacturer's instructions when restarting.

Should I drain the water heater?

Generally not for a slab leak. Draining is a separate task and is not needed just because the inlet is closed.

My water heater is strapped to the wall. Does that change anything?

No. Seismic strapping is required in California and stays in place. Shutting the inlet does not affect it.

General information for Yorba Linda, not a quote or professional advice. In an emergency, call 911.