Roughly one in five Washington County homes is not somebody's primary residence. Most of the advice written for those owners is about freezing pipes, which is a northern problem transplanted to a place where it barely applies. The season that empties these houses is summer, and summer here is the hard one.
The Washington County Water Conservancy District has the clearest statement of what actually happens. Seasonal residents who occupy a home about half the year use only ten percent less water annually than full time residents, because the landscape gets irrigated year round for an empty house. The District's general manager put the reason plainly: owners show up on a weekend and they want that landscaping to look perfect. So the house sits closed from roughly Memorial Day to October with the water on, the controller running, and nobody in it. Everything below follows from that.
What the house is sitting through while you are gone
St. George recorded 98 days at or above 100 degrees in 2024, and it has now had back to back hottest Julys on record in 2023 and 2024. The all time high is 117 degrees, set in July 1985 and matched on July 11, 2021. That is the heat side.
The water side is stranger. June is the driest month of the year at 0.16 inches of precipitation, half of May, a third of July and an eighth of February. August is the second wettest at 1.07 inches, behind February's 1.38 inches, and August delivers it in convective bursts rather than as steady rain. The monsoon season runs officially from June 15 to September 30 and generally reaches Utah after about the Fourth of July. Storms fifteen to twenty miles upstream can flash flood a wash with no visible rain over your house at all.
So the empty months are the hottest of the year and contain the most abrupt rainfall of the year. A closed house gets both, and there is nobody there to notice either.
The main shutoff is the whole strategy
One decision does more than everything else combined: turn the water off at the house before you leave. A supply failure in an occupied house is a bad afternoon. The same failure in a house nobody enters for four months is a different kind of event entirely, and the difference is not the pipe. It is the elapsed time.
The standard national advice for finding a shutoff is to check the basement, which is useless here. Slab-on-grade construction dominates and there is usually no basement and no crawlspace. There are up to three valves and you should know all three.
The curb stop sits in a plastic or concrete box at the property line, usually in the park strip or near the sidewalk, and it takes a long T handled meter key to operate. The valve on the street side of the meter belongs to the city, and city side work goes through St. George Water Services at 435-627-4802.
Your own main shutoff is somewhere on the house side. In slab-on-grade construction in this climate it turns up most often at or near the front hose bib where the service line comes up through the slab or the wall, sometimes in a small access box or behind a removable panel; in the garage, on the wall shared with the front of the house, often near the water heater or the softener loop; or in an interior utility closet. Then there is the cold inlet valve at the water heater and the angle stops under every sink and toilet.
Two things to do about it before the summer you actually need them. Find the main shutoff and tag it, which takes two minutes on a Saturday. And turn it all the way off and back on once a year. Gate valves seize in high dissolved solids water, and St. George runs between 118 and 936 parts per million depending on which source blend feeds your street. A valve nobody has touched in fifteen years has a real chance of not turning, or of the stem packing letting go the moment it does. Finding that out in April is a repair. Finding it out during a leak is a flood.
The water heater
There is no reason to keep a tank of water hot for four months for nobody. Close the cold inlet valve to the heater and take the appliance out of service: on a gas unit that means setting the gas control to off, and most heaters have a vacation or lowest setting for shorter absences.
The heater also gives you a reason to be careful about the order you do things in when you come back. Turn the water on and let the tank fill completely and the air purge out of the hot side before the heater goes back into service. Run the hot taps until they run clear and steady, then relight.
One note specific to tankless owners. Two of the major manufacturers void coverage at 12,000 operating hours regardless of calendar years, and a unit fouled with scale runs longer per gallon delivered to reach the same setpoint. Time away from the house does not add hours, which is the one advantage of the arrangement. What it does not do is stop the scale that is already there, so a part time house on this water still needs the same descaling attention as a full time one, just on your schedule rather than the calendar's.
What a small leak does to an empty house
Mold colonizes wet cellulose in roughly a day or two. The one genuine local advantage is that ambient humidity here is low, so a wet house dries faster than it would almost anywhere else in the country. But that only helps if air movement and dehumidification start immediately, and in an empty house nothing starts at all.
The second consequence is under the floor rather than on it. Collapsible soil is mapped across this area, and the Utah Geological Survey defines it as soil with considerable strength while dry that settles significantly through hydrocompaction when wetted. In a neighborhood the wetting agent is almost always a leaking irrigation line, a failed service line, a downspout discharging at the foundation, or a broken sewer lateral. The loop runs leak, localized wetting, settlement, more pipe breakage, more leak. Four months is plenty of time for it to run several laps.
Utah's own hazard plan carries the extreme version of this. On January 19, 2013 at around three in the morning, a boulder twelve feet by nine feet dislodged from sandstone within Foremaster Ridge and crashed into a house, seriously injuring a woman. The State Hazard Mitigation Plan attributes it to a 40,000 gallon water leak associated with a house on top of the ridge. That is a state document, about St. George, about an undetected residential leak.
Before you leave, there is a two minute check anyone can do. Shut off every fixture, then watch the meter. If the low flow indicator moves over half an hour with nothing running, something is running.
Devices that watch the house for you
If shutting the water off entirely is not practical, because someone comes by or the house has a pool or the irrigation is fed off the same line, an automatic shutoff valve is the substitute. These are not all the same thing and the difference matters.
The important distinction is between monitoring and protection. A device that straps to the meter and tells you your usage has told you something after the fact. A device with a motorized valve in the line can close it.
| Device | How it detects | What to know |
|---|---|---|
| Moen Flo | Flow, pressure and temperature on the main, plus a nightly test that pressurizes the system and watches for decay | Motorized ball valve, auto shutoff on catastrophic flow, app alerts. Needs a 120 volt outlet in reach and WiFi at the install point |
| Phyn Plus | High frequency pressure wave analysis, sampling pressure hundreds of times a second | Fingerprints individual fixtures and can often tell you which one is leaking. Same shutoff capability and similar install requirements |
| Water Hero | A pulse sensor reading the existing meter | A retrofit actuator that clamps onto the existing main shutoff valve. No pipe cutting, which is the right answer when the shutoff is in an awkward spot |
| Flume | Straps to the meter | Monitoring only. No shutoff. Useful, but it is not protection |
The irrigation tee, and the decision most installers get wrong
In a market where nearly every house has an irrigation system, where the valve goes relative to the irrigation tee is not a detail. Install it upstream of the tee and the device protects the irrigation system too, which sounds better until a stuck open zone valve or a broken head triggers a shutoff and the house loses water while you are in another state. Install it downstream and the house is protected and the irrigation is invisible to the device.
Most installs here belong downstream of the irrigation tee, with irrigation leaks handled by a flow sensor on the controller instead. Getting it backwards produces either nuisance shutoffs or a false sense of coverage, and you will not find out which until you are eight hundred miles away.
The landscape, which is where the water is actually going
The District's ten percent finding is the real headline for a part time owner. The house being empty barely moves the annual water bill because the yard does not know you left. An irrigation audit before you go is worth more than any single plumbing item on this list: check the controller schedule against the season, look for the zones that have quietly been running twice, and check the drip. Thin wall poly tubing and emitters sit fully exposed to the sun and are the most common failure item in a drip system, and rodents chew soft tubing to reach water.
One more setting worth changing before you go. A water softener on a time clock regenerates on a schedule whether or not anyone is using water, so it regenerates all summer for an empty house. That wastes salt, and every unnecessary regeneration puts chloride into a sewer system whose treated effluent is reused for irrigation. The City asks residents to keep softener settings low for exactly that reason. A demand initiated softener regenerates on measured volume and simply stops when the house does.
What we’d do at your house
We find and tag the main shutoff, then operate it in front of you so you know it works before you rely on it.
We check the meter with everything off, and if the indicator moves we look for the leak before you leave rather than after.
We take the water heater out of service properly and tell you the order to bring it back in when you return.
If you want an automatic shutoff valve, we install it downstream of the irrigation tee and explain what that does and does not cover.
We audit the irrigation controller and the drip before you go, because that is where the water bill actually is.
If the softener is on a time clock, we say so, and we tell you what the City asks residents to do about salt.
We put the whole shutdown on one page you can hand to whoever is watching the house.
Sources
What this page says comes from the documents below, read in full. It describes them. It is not legal advice. Confirm with your association, your city, or an attorney before you act.
- WCWCD finding that seasonal residents use only ten percent less water annually, and the general manager's quotation; roughly 20 percent of county homes not primary residences playbook.txt §5
- Heat and precipitation: 98 days at or above 100F in 2024, back to back hottest Julys, 117F on July 11 2021 05-environment-water-geology-corpus.md §3.1
- Bimodal precipitation, June 0.16 inches, August 1.07 inches, February 1.38 inches; monsoon June 15 to September 30, arriving after roughly July 4; upstream storms flash flooding with no local rain playbook.txt §5
- Where the main shutoff is in a slab-on-grade home; curb stop and city side ownership; St. George Water Services 435-627-4802; tag it and exercise it annually; gate valves seizing in high TDS water 01-plumbing-corpus.md §8.2
- St. George TDS range 118 to 936 ppm 05-environment-water-geology-corpus.md §1.2
- Taking the water heater out of service: close the cold inlet, gas control off; water heater to vacation mode as part of a seasonal close-up 01-plumbing-corpus.md §8.4; playbook.txt §5
- Rinnai and Rheem 12,000 operating hour warranty caps and the scaling effect on the hours clock 01-plumbing-corpus.md §1.1
- Water damage response: mold timing, low ambient humidity, air movement 01-plumbing-corpus.md §8.4
- Collapsible soil, hydrocompaction, and the leak to settlement feedback loop 05-environment-water-geology-corpus.md §2.5
- Utah State Hazard Mitigation Plan, Foremaster Ridge rockfall, January 19 2013, attributed to a 40,000 gallon leak 05-environment-water-geology-corpus.md §2.8; playbook.txt §4
- Meter low flow indicator check 01-plumbing-corpus.md §5.1
- Smart shutoff devices: Moen Flo, Phyn Plus, Water Hero, Flume; the irrigation tee installation decision 01-plumbing-corpus.md §8.5
- Softener regeneration types and the reclaimed irrigation water salt concern 01-plumbing-corpus.md §2.1; 05-environment-water-geology-corpus.md §1.1
- UV exposure of drip tubing and emitters as the most common failure item 05-environment-water-geology-corpus.md §3.5