What Stops Working in a Power Outage: Your Home Plumbing During a PSPS
Californians have gotten used to planning around Public Safety Power Shutoffs — charging devices, moving food, filling the car. Plumbing rarely makes the list, and it should, because a house on a private well loses all water the moment the power drops, and a house on a sewage ejector pump can back up onto the floor within hours of normal use. Six investor-owned utilities are authorized by the CPUC to conduct PSPS events in California: PG&E, Southern California Edison, San Diego Gas & Electric, Liberty Utilities, Bear Valley Electric Service and PacifiCorp. Here's what your plumbing actually does when they pull the switch.
What stops working immediately
- A private well pump. This is the big one, and the CPUC says it plainly in its own PSPS FAQ: water and gas should stay on during a shutoff, but if your water requires an electric pump — a well system, or a high-rise booster — it goes off too. Submersible and jet pumps are electric, so no power means no water at any tap, not reduced pressure. Whatever is in the pressure tank is what you have, typically a few minutes of normal use.
- Sewage ejector and grinder pumps. If a bathroom, laundry or garage conversion sits below the sewer line, its waste is pumped, not gravity-fed. Wastewater keeps arriving in the basin by gravity while the pump sits idle, and once the basin fills, the lowest fixture is where it comes back out. The correct move during an outage is to stop using those fixtures entirely — see our comparison of sump pumps and sewage ejector pumps if you're not sure which one you have.
- Sump pumps, for the same reason — which matters most when the outage overlaps with a storm.
- Gas tankless water heaters. Counterintuitive but true: they need electricity for electronic ignition, the combustion blower, the sensors and the control board. Rinnai states it directly — without power to the unit, you get no hot water. Battery backup accessories exist, but they are an add-on, not standard.
- UV disinfection systems. The safety-critical one. UV leaves no residual disinfectant downstream, so the moment the lamp is off, water passing through is untreated. On a well with UV as the primary treatment, an outage means the water should be treated as unsafe until the system is running and the lines have been flushed.
- Recirculating pumps, booster pumps and macerating (upflush) toilets — all motor-driven, all stop.
- Smart shutoff valves, depending on the model. Flo by Moen, for example, does not close the water automatically during a power outage unless the optional lithium-ion battery backup is fitted, which is rated for about four hours; there's a manual knob for turning water off by hand. Check your own device's documented behavior rather than assuming — our smart leak detector and shutoff valve guide covers the category.
What keeps working
- City water pressure, usually — at least at first. Distribution systems run largely on gravity from reservoirs and elevated tanks, and California regulation (Title 22, section 64602) requires systems to maintain at least 20 psi at the service connection at all times.
- Gravity drainage to a street sewer. Only pumped waste fails.
- An atmospheric gas storage water heater with a standing pilot. The pilot burns continuously and the gas valve runs on the millivolts the thermocouple generates — no house current needed. But check before you rely on it: many newer gas tanks use electronic or hot-surface ignition and will not light without power, and power-vent and direct-vent gas tanks need their blower. An electric tank stops heating immediately but holds a tankful of hot water for many hours.
Can the city water itself fail? California has the receipts
Yes — and the examples are local, not hypothetical. During the October 26–28, 2019 shutoff, PG&E de-energized the raw water pumping complex serving Vallejo; the city declared a water emergency, and its operations manager described being down to about two days of water left. On October 9 that year, American Canyon had to be supplied through Vallejo's intertie because its own backup generator had failed. A Cal OES legislative report on PSPS documents Calistoga's High Street tank being depleted during extended outages, leaving a residential area without water — the city resorted to using a fire engine as a bypass pump every two to three days.
The mechanics are three-fold: pressure zones fed by booster pump stations lose flow quickly without on-site generation, elevated tanks draw down and aren't refilled without pumping, and if pressure falls far enough, contamination can be drawn in through joints and cracks. California codifies the consequence — the State Water Board's guidance on unsafe water notices lists system pressure falling below 5 psi as a result of events including power outages as a Tier 1 trigger, and Title 22 requires systems to maintain at least 20 psi at the service connection at all times. Our guide on what to do during a boil water notice covers the household side.
Two structural facts worth knowing: storage requirements are thinner than most people assume — under Title 22 section 64554, systems with 1,000 or more connections need only enough storage for four hours of peak hourly demand — and California has no general backup-power mandate for water systems. The state has funded generators through Cal OES resiliency grants and a State Water Board program aimed at small disadvantaged-community systems, but whether your water agency can ride out a multi-day outage is an agency-by-agency question worth asking yours directly.
How long you should actually plan for
PG&E's own figures, filed with the SEC, are the cleanest numbers available. In 2019, across seven events affecting roughly two million customers, the average outage lasted about 43 hours, with average restoration of 17 hours once the weather all-clear came. In 2020 it was 35 hours (10 to restore); in 2021, 31 hours (12 to restore). Note that outage duration and restoration time are two different measurements — restoration only starts counting after the wind event ends.
Recent events have been far smaller. PG&E's May 2026 shutoff affected 4,583 customers with average restoration around three hours, and its July 2026 event 5,186 customers at 3.6 hours. That's the realistic modern shape: fewer people, shorter durations — with the 2019-scale event still the one to plan against if you're on a well. You will get warning: CPUC guidelines require notice 48 to 72 hours ahead to public safety partners, 24 to 48 hours to affected customers, and again one to four hours before de-energization.
Does any of this actually hurt people?
The best evidence says yes, for older adults specifically. A 2025 study by Harding and colleagues in Disaster Medicine and Public Health Preparedness examined emergency department visits across 56 California counties during the fall 2019 PSPS events and found roughly 15 additional ED visits per 100,000 people aged 65 and over on the days of highest shutoff exposure, with increases in respiratory, cardiovascular, injury and mental/behavioral diagnoses (study on Google Scholar).
On the water side, there is no peer-reviewed study specific to private wells failing during PSPS events — that literature simply doesn't exist yet, and it's more honest to say so than to fill the gap with a blog post. What does exist: a 2022 study by Klise and colleagues in the Journal of Water Resources Planning and Management simulated long-duration power outages on a real potable water system and quantified the resulting losses in water delivery and quality (study on Google Scholar), and a 2020 study by Pauloo and colleagues in Environmental Research Letters documented how fragile California's domestic wells already are, reproducing more than 2,000 observed well failures in the 2012–2016 drought and projecting thousands more in the Central Valley by 2040 (study on Google Scholar).
What to do before the next one
- Store water for flushing, not just drinking. Ready.gov's baseline is one gallon per person per day for several days. Day counts differ between official sources — PG&E says three days, the State Water Board a week, some counties two weeks — so pick the longer end if you're on a well. Toilets are the volume you'll underestimate; a few filled buckets pour-flush a household through a two-day outage.
- Fill the tub and containers when a PSPS is announced, especially on a well — PG&E's own well-water preparedness sheet says exactly this. PSPS events come with notice; unplanned outages don't.
- Sort out generator power for the well pump properly. A transfer switch or interlock kit — roughly $400–$900 for an interlock, $1,000–$2,200 for a manual transfer switch installed — keeps you from backfeeding the grid and endangering line crews. Pump manufacturers treat this as mandatory, not optional: Franklin Electric's manual carries an explicit warning that a transfer switch must be used any time a generator backs up the line. Sizing is not guesswork either — Franklin publishes minimums because the generator has to deliver at least 65% of the motor's rated voltage during starting to produce starting torque: about 2 kW for a 1/2 hp pump, 4 kW for 1 hp, 5 kW for 1.5 hp, 7.5 kW for 2 hp on a three-wire motor (two-wire motors need more). Operating order matters too — start the generator before the pump, and stop the pump before the generator; letting a generator run out of fuel with the motor running can damage the pump's thrust bearing. This is licensed-electrician work, and it pairs with the gas side covered in our standby generator gas line guide. PG&E currently offers a $300 rebate toward a qualifying generator or battery, with an extra $200 for CARE and FERA customers.
- Add backup to a sump or ejector pump. A battery backup system runs roughly $600–$2,000 installed; a water-powered backup runs about $300–$1,000 and needs no electricity at all — but it works off municipal water pressure, so it is useless on a well. Our sump pump battery backup guide goes through the choice.
- Know which water heater you own. Look for a standing pilot versus an electronic igniter. If it's electronic, hot water is going away with the power, and relighting takes the control board coming back.
After the power comes back
On city water, run a cold tap for a few minutes and watch for discoloration from disturbed sediment.
On a well, the pressure question is the one that matters. Keeping the system pressurized is what forms the physical barrier against contaminants entering through the wellhead and plumbing; when pressure is lost, bacteria and viruses can find their way in. That's the reasoning behind two pieces of official guidance worth following. First, the CDC's simple field test: run a faucet and watch for water spurting intermittently as air escapes — spurting indicates the well and household plumbing lost pressure. Second, San Luis Obispo County's rule, which is stricter than most and sensible: a well must be disinfected after flooding, repair, maintenance, contamination, or if the water system has lost pressure.
So: if the system was depressurized, don't drink the water until you've flushed the system and, ideally, tested it. Boiling at a rolling boil for one minute is the CDC's interim step — note that official sources genuinely differ here, with some state and county guidance calling for five or ten minutes. Where disinfection is warranted, the standard advice is to wait seven to ten days afterward before sampling. If you have UV treatment, remember it leaves no residual protection and let the lamp reach full output before drawing water for consumption. Our guide to private well water testing covers what to test for and what it costs.
Also watch the well pump itself in the days after: a rough restart is exactly when a marginal pump or pressure tank gives up, as our well pump replacement cost guide explains.
The short version
If you're on city water with a gravity sewer and a standing-pilot gas tank, an outage is an inconvenience. If you're on a well, have a pumped sewer connection, run a tankless heater, or rely on UV, an outage is a plumbing event that needs a plan. Getting that plan in place — a transfer switch, a pump backup, a stored water supply — is a few hundred to a couple of thousand dollars, and it's cheapest to sort out in the months when nobody is asking for it. If you want it looked at before fire season peaks, describe your setup on Plumber Comparator and request a free quote; we work with plumbers across California's outage-prone areas, from Redding and Chico to Santa Rosa.
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