Yes — if you're leaving for more than a long weekend, close the main shutoff. It takes about thirty seconds, it costs nothing, and it converts the single most expensive thing that can happen to an unoccupied house into a non-event. For trips under two or three days, closing the washing machine valves and the ice maker line covers most of the realistic risk.
The reasoning is simple. A washing machine hose rupture at 60 psi releases roughly 500 gallons per hour. A failed ice maker line runs slower, but it runs for days, and it does its damage under the subfloor where nobody sees it. Water damage is the most common homeowner insurance claim there is, and an unoccupied house removes the one thing that limits the damage — somebody noticing.
What the five steps below actually require isn't tools. It's knowing where your shutoffs are and whether they still work, because a valve that hasn't moved in eight years may not move when you need it to.
Step 1: Close the main shutoff
The main shutoff kills water to the entire house from a single point. In most South Bay homes built before 1980 — including the post-war tract homes common across Hawthorne's Hollyglen neighborhood and the 1950s ranch stock throughout Gardena's Moneta area — that valve is either a gate valve (round wheel handle) or a ball valve (lever handle) located near the water meter or where the supply enters the house.
Gate valves fail in partially open positions. If yours requires more than four full clockwise rotations to close, or if it closes but water still trickles through, the gate is worn. That's worth knowing now, not at 10 p.m. the night before a two-week trip. If the main shutoff is unreliable, the solution isn't to skip this step — it's to get the valve replaced before you leave.
After closing the main, open a faucet on the lowest floor and let it drain to zero. That depressurizes the system and confirms the valve is actually holding. If the faucet keeps flowing after 30 seconds, the valve isn't seating. Call that in before you go.
Step 2: Isolate the water heater
Water heaters have two shutoffs: a cold-water supply valve on the inlet pipe above the unit and a gas valve or breaker for the heat source. When the main is off, the tank holds its contents but the heating element or burner has no reason to run. If you're leaving for more than five days, turn the thermostat to the pilot or vacation setting rather than shutting the gas entirely — relighting a standing pilot after a week is straightforward; restarting a fully extinguished system on a tankless unit is slightly more involved.
In Redondo Beach coastal zones, where salt air accelerates corrosion on brass fittings and anode rods degrade faster than inland cities, the inlet supply valve deserves a close look before any vacation shutdown. A corroded valve that partially fails under no-flow conditions can dump water into the pan and overwhelm the drain. If the valve hasn't been exercised in years, turning it now is better than finding out it leaks when you return. Our [water heater service](/services/water-heaters) includes supply valve inspection as part of any heater maintenance call.
Step 3: Turn off the washing machine valves
Washing machine supply hoses are the single most common source of catastrophic interior water damage in residential properties. Industry loss data consistently points to hose failure — particularly on rubber hoses over five years old — as a leading cause of five-figure water claims. The valves are the two threaded knobs or levers on the wall behind the machine: hot on the left, cold on the right.
In older homes with original galvanized supply lines — common in pre-1970 Lawndale slab homes and Hawthorne tract homes from the aerospace-worker housing era — these shutoff valves may not have been turned since installation. Exercise them before your trip, not during. If a valve won't close fully or spins without seating, it needs replacement. A valve that won't close isn't a shutoff.
If the machine is on an upper floor, the case for shutting those valves gets more urgent. A first-floor laundry failure is bad. A second-floor failure sends water through ceiling joists into the room below and can compromise structural sheathing before anyone sees it from the outside.
Step 4: Kill the ice maker line
Refrigerator ice maker lines are a slow-failure risk. They're typically 1/4-inch OD plastic or braided steel — small diameter, low volume, but they run at full supply pressure and connect with compression fittings that can loosen over time. A pinhole failure in a line tucked behind the refrigerator can drip at a rate that saturates the subfloor over several days without pooling visibly.
The shutoff for the ice maker is usually either a dedicated valve on the cold-water supply line behind the fridge or a saddle valve tapped into a nearby copper line. Saddle valves — the type that punctures the pipe with a needle — are prone to mineral buildup and partial failure. If yours is a saddle valve, turning it off and back on annually keeps it exercised. If it won't close fully, that's an upgrade conversation worth having before the next trip. Disconnecting the fridge from the wall and pulling the line to inspect the compression fitting takes two minutes and is worth doing at least once a year.
Step 5: Check under sinks and behind toilets
Supply stops — the small angle valves under kitchen and bathroom sinks, and the shutoffs behind every toilet — are the least-inspected valves in most homes. They're also among the most likely to fail when disturbed after years of inactivity. This step isn't about closing them for the trip; it's about confirming they aren't already weeping at the braided supply hose connection or at the packing nut.
Walk every bathroom and the kitchen. Look for mineral deposits around the valve body (a white or green crust), soft spots in the cabinet floor, or discoloration on the cabinet wall behind the toilet tank. Any of those is a sign of a slow drip that's been accumulating. A trip away doesn't cause that failure — it just means no one is there to put a towel down when it becomes a full drip.
For Lomita and [Torrance general plumbing](/service-areas/torrance/general-plumbing) calls, this under-sink inspection is something the Mainline crew runs through on any routine service visit. If you haven't had eyes under those cabinets recently, a pre-vacation general inspection is a reasonable use of an hour.
The case for a pre-trip plumbing check
The five steps above are self-service — no plumber required. But if your home has any of the following conditions, a 30-minute professional walk-through before an extended absence is worth scheduling: galvanized supply lines anywhere in the system, a water heater over 10 years old, known or suspected slow drips you've been monitoring, or any supply valve that hasn't been exercised in more than five years.
Homes in older South Bay neighborhoods carry compounded risk. An Old San Pedro house from the 1920s, a post-war Hollywood Riviera bungalow, or a mid-century Gardena tract home may have original shutoff hardware that's technically functional but fragile under sudden movement. Exercising those valves and confirming system integrity before a two-week absence is a different conversation than doing it during an emergency.
Licensed C-36 #901735 general plumbing service is available across all 16 South Bay cities we serve. Our [general plumbing services](/services/general-plumbing) page outlines what a pre-trip inspection covers and how to schedule one.
What to do next
If you're leaving in the next week and haven't confirmed your main shutoff seats cleanly, your water heater supply valve moves freely, and your washing machine shutoffs actually close — do those checks today. It takes five minutes and the cost of getting it wrong is measured in months of disruption.
If any valve fails the test or you want a set of professional eyes on the system before an extended absence, call the Mainline crew at (310) 808-7343. We dispatch 24/7, target a 60-minute response for emergencies, and charge no overtime fees. A pre-trip inspection during normal hours is a straightforward scheduling call.
Frequently Asked Questions
Should I turn off the water when I go on vacation?
For any trip longer than a long weekend, yes. Close the main shutoff, then open a low faucet to depressurize the system. For shorter trips, closing the washing machine supply valves and the ice maker line covers most of the realistic failure risk with less hassle.
What should I do with the water heater if I shut off the main?
Turn the thermostat to its vacation or pilot setting rather than shutting the gas off entirely. The tank holds its contents with the main closed and the burner has no reason to fire. Relighting a standing pilot after a week is straightforward; fully restarting a tankless unit is more involved.
What if my main shutoff valve won't close all the way?
That's a failed valve and it needs replacing before you travel, not after. Gate valves — the ones with a round wheel handle — commonly fail in a partially open position. If yours takes more than four full turns to close, or water still trickles after 30 seconds with a faucet open, the gate is worn through.
Do I need to drain the pipes after shutting off the water?
Not in the South Bay. Draining matters in freezing climates. Here, opening one low faucet until flow stops is enough — it depressurizes the system and confirms the main is actually seating rather than just feeling closed.
Which valve fails most often in an empty house?
Washing machine supply hoses, by a wide margin, particularly rubber hoses more than five years old. Second is the ice maker line, especially where it connects through a saddle valve — the type that pierces the pipe with a needle. Saddle valves clog with mineral buildup and often won't close fully.
How long can a slow leak run before it does real damage?
A pinhole in a 1/4-inch ice maker line can saturate a subfloor in two to three days without ever pooling where you'd see it. That's the case for shutting supply lines rather than trusting that a small leak stays small — nobody is home to put a towel down.
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