Water damage is one of the most common ways a vacant house gets expensive, so shutting the water off before a long trip is sensible for many homes. But it isn't a one-step answer, and some parts of a house depend on water. This guide goes through the tradeoffs. It's general information, not a substitute for a plumber who has seen your house.
The domestic main shutoff
Closing the main valve stops pressurized water from reaching fixtures, appliances, and the water heater, so a failed supply line or fitting can't run for weeks. That's the main benefit. The tradeoff is everything downstream that needs water, covered below. Make sure you know where the valve is, that it works, and what else it affects before you leave, since an old valve can stick or leak when turned.
Irrigation systems
Depending on how the house is plumbed, irrigation may or may not shut off with the main. Shutting it off in Phoenix summer heat can kill trees and plants that would have survived with water; leaving it on means a cracked line or stuck valve can run unnoticed. Many owners keep irrigation running on a reduced schedule and have someone check the yard. Ask your landscaper what the plants can tolerate.
Pool equipment
Evaporation in Arizona is fast. If the pool has an automatic fill and you cut the water, the level can drop until the pump runs dry, which can damage equipment. Coordinate with your pool service before you shut anything off.
Water heaters
If you close the water supply, the water heater may need to be turned off or set to a vacation mode, particularly an electric unit whose elements shouldn't run without water around them. Follow the manufacturer's instructions or ask a plumber. The heater is also a common source of leaks, so it deserves a look.
Refrigerator and ice maker lines, and appliance hoses
Small supply lines to refrigerators and ice makers, and the hoses behind washing machines and dishwashers, are everyday failure points. Closing the main covers them. If you leave the water on, closing the individual shutoff valves at those appliances is a reasonable extra step, and braided or aging hoses are worth replacing before a long absence.
Toilets and drain traps
Turning off the water doesn't stop the drains from drying out. In Arizona's dry air, the water in a drain trap that keeps sewer gas out can evaporate over weeks. Toilet tanks can also develop slow leaks that keep draining. Running each drain before you leave and checking periodically helps, as covered in our summer checklist.
Fire-suppression systems
If your home has a residential fire sprinkler system, don't shut off its supply or change it without checking first. The system may be required by code or by your insurer, and it may be on a separate valve. Talk to a licensed fire protection contractor or the original installer before touching it.
When to call a professional
If you're unsure what shutting off the main will affect, ask a licensed plumber to walk through the house with you before you leave. Ask your pool, landscape, and fire-protection professionals about their own systems, and check your insurance policy for conditions that apply to a vacant property.
Shutting off the water doesn't replace checking the house
Even with the main closed, problems that don't depend on the supply line can still happen: air conditioner condensate overflow, roof or window leaks after a monsoon storm, a failed refrigerator, pests, or a power outage. A closed valve reduces one kind of risk. It doesn't tell you what the house looks like.
That's what Home Watch is for: a scheduled walk-through with a photo report, whatever you decide about the water. You can see an example report, compare plans and pricing, or read about Home Watch in Scottsdale and Phoenix.