Most plumbing does not use electricity, but some of the most important systems attached to it do. Water moves through pipes on pressure, so faucets, gravity-flush toilets, and drains keep working when the power goes out. Catchment pumps, booster pumps, tankless water heaters, and UV disinfection systems are a different story: they stop the moment the lights do. The Hawaii Department of Health recommends filtration and disinfection for all catchment water used at home, which means a power outage is not just a comfort issue on a catchment property, it is a water safety issue until the UV system is back online.
On the Big Island, the answer to whether plumbing uses electricity varies more than almost anywhere else in the country, because how your home gets its water determines almost everything about what an outage means for you.
Where Plumbing and Electricity Overlap in Your Home
Pipes, fittings, and fixtures are passive. They draw nothing. The electricity in a plumbing system goes to the equipment that heats, moves, and treats water. According to the Department of Energy, water heating alone accounts for about 18 percent of a typical home’s energy use, usually making it the second largest energy expense in the household. Add a catchment pump, a pressure tank, a garbage disposal, and a hot water recirculation pump, and plumbing-related equipment can quietly become one of the biggest electrical loads you own.
A pressure tank is the tank that holds water under air pressure to maintain consistent flow between pump cycles in a catchment system. When the pump stops, the pressure tank delivers the last of its stored pressure until the tank empties. That is why a catchment home does not go completely dry the instant power fails: it has a few flushes of pressure left.
That connection between plumbing and electricity matters most on the day the power fails. Knowing which side of the line each part of your system sits on tells you exactly what to expect.
County Water or Catchment: The Difference That Decides Everything
County Water Homes
If your home is connected to the county water system, you will almost always keep cold water during an outage. The mains stay pressurized by the utility, so faucets run and toilets refill without any help from your electrical panel.
Rainwater Catchment Homes
Rainwater catchment is the system that collects rooftop runoff into a large storage tank, with an electric pump pressurizing the house from that tank rather than drawing from a utility main. When the power goes out, the pump stops and your fixtures go dry within a flush or two as the pressure tank empties.
The filtration side matters just as much. UV disinfection is a water treatment method that uses ultraviolet light to destroy bacteria, viruses, and other pathogens in the water line, and the protection only exists while the UV light has power. The Hawaii Department of Health recommends filtration and disinfection for catchment water used at home, and if your UV light has been off during an outage, treat the water as untreated until the system has run properly again after power returns.
Catchment systems also need routine maintenance that has nothing to do with outages.
A Clogged Catchment Filter in Hilo, Resolved the Same Day
Ludmilla Muns had never operated a catchment home before. When a stretch of heavy rain clogged her filters and the taps slowed to a trickle, she did not know where to start, which is a stressful place to be when a water supply system is not working and the issue is unfamiliar.
Our technician Steve responded quickly, took care of the clogged filters, and explained how the system worked as he went. In her words, he “was very informational and helpful” and patient with every question she had. Read Ludmilla’s full Google review.
She ended the visit with the filter issue resolved and a clear understanding of how her own system runs. That is the outcome we aim for on every catchment call: the immediate problem fixed and the homeowner confident about what they are managing. If your filters, pump, or whole house filtration setup needs attention, that is work we handle year-round.
Hot Water During an Outage: Tank vs. Tankless
Tank Water Heaters
A standard tank water heater is the most outage-friendly option. An electric tank cannot reheat without power, but the 40 to 50 gallons already in the tank hold useful heat for a day or so if the household is careful with usage. A gas tank heater with a standing pilot keeps making hot water like nothing happened.
Tankless and Solar Water Heaters
Tankless units are a different case. Electric tankless heaters stop the moment power drops. Most gas tankless models stop too, because they rely on electronic ignition and control boards rather than a standing pilot. A thermosiphon solar water heater is a passive system that circulates water by natural convection as the sun heats it, with no pump or electricity required. These systems, which are common across Hawaii, usually keep delivering hot water through an outage without interruption. Pumped solar loops, by contrast, pause until power returns.
If you are weighing a tankless water heater installation against a conventional tank water heater, outage behavior deserves a spot on your list alongside efficiency and space savings.
What Keeps Working and What Stops: A Big Island Quick Reference
Here is the breakdown for Big Island homes, organized by how each system behaves the moment power goes out.
| Plumbing component | Power outage behavior |
|---|---|
| Faucets and showers on county water | Keeps working; utility maintains line pressure |
| Gravity-flush toilets on county water | Keeps working; tank refills from pressurized mains |
| Sink and tub drains | Keeps working; gravity-fed, no electricity involved |
| Gas tank water heaters with standing pilots | Keeps working; no electricity required |
| Passive thermosiphon solar water heaters | Keeps working; circulates by convection without a pump |
| Electric tank water heater | Works briefly; stored hot water holds heat for roughly a day |
| Catchment or booster pumps | Stops immediately; pressure bleeds off within a flush or two |
| UV disinfection systems | Stops immediately; water is unprotected while power is off |
| Electric tankless water heaters | Stops immediately; requires power to operate |
| Gas tankless water heaters (electronic ignition) | Stops immediately; control board requires power |
| Garbage disposals | Stops immediately; electric motor with no manual alternative |
| Sewage ejector pumps | Stops immediately; do not send wastewater down until power returns |
| Pump-assisted or upflush toilets | Stops immediately |
Which Plumbing Problems Become Urgent When the Power Is Out
A few situations need fast attention rather than patience.
A catchment home with no stored drinking water needs a plan within hours, not days. A sewage ejector pump is a pump that moves wastewater from fixtures located below the main sewer line up to the drain. When power fails, the holding basin can overflow if wastewater continues to enter it, so the right call is to stop sending anything down those drains until power returns.
When power does come back, watch your water heater and pump. Electric heating elements can fail if a tank drained during the outage and the element was energized without water around it. Pumps that short-cycle or will not build pressure after an outage are indicating a problem worth having inspected rather than ignored. Our emergency plumbing team answers around the clock for exactly these calls.
A little preparation goes further than any repair. Store a few days of drinking water if you are on catchment, know where your main shutoff and pump breaker are, and consider surge protection for pump and water heater circuits, since power rarely returns cleanly after an outage.
The Bottom Line for Big Island Homeowners
Walk your home once with fresh eyes and sort every water-related device into powered or not powered. That ten-minute exercise tells you exactly what an outage will look like at your address, and it usually reveals the one weak link worth addressing in advance. As a licensed and insured Hawaii contractor, All Aloha Plumbing has helped homeowners across Hilo and Kailua-Kona get outage-ready.
If you want a professional set of eyes on your pump, water heater, or filtration setup, request a service visit and we will bring the aloha to you.
Frequently Asked Questions
Will my toilet flush during a power outage?
A gravity-flush toilet flushes as long as the tank can refill, and county water keeps doing that during an outage because the utility maintains pressure in the mains without any electricity at your home. On a rainwater catchment home the situation is different: you get a flush or two before the pressure tank empties, after which you can refill the tank manually with stored water to keep flushing. Pump-assisted or upflush toilets stop working immediately when power fails because they rely on an electric pump to move waste. Knowing which type you have is one of the most practical things a new catchment homeowner can establish.
Does a gas water heater work without electricity?
A gas tank water heater with a standing pilot keeps working normally during a power outage, because the standing pilot ignites the burner mechanically without any electrical signal. However, most modern gas tankless water heaters rely on electronic ignition and a control board that requires electricity to operate, so they stop just like an electric unit when power fails. If outage resilience matters to you, a gas tank heater with a standing pilot or a passive thermosiphon solar system are the two options that deliver hot water reliably through an extended outage without any backup power.
Is catchment water safe to drink right after an outage?
Not immediately. UV disinfection uses ultraviolet light to destroy bacteria and pathogens as water passes through the treatment unit, and that protection is only active when the system has power. After any outage, run the UV system for the manufacturer’s recommended flush time before treating the water as safe to drink. The Hawaii Department of Health recommends keeping stored drinking water on hand for exactly this situation. Until the UV system has been running properly again, use stored or bottled water for drinking, cooking, and brushing teeth.
Can I run my catchment pump on a generator?
Usually yes. Most residential catchment pumps draw modest wattage that a portable generator can handle, though the starting surge when the pump motor kicks on requires a generator with enough reserve capacity. The critical safety step is having a licensed electrician set up a proper transfer switch or connection point before you need it, rather than improvising extension cords during an outage, which can backfeed into utility lines and create a hazard for lineworkers. A correctly wired generator connection also protects the pump motor and control board from the irregular power that can come from a generator without proper conditioning.
Should I do anything to my plumbing when the power comes back on?
Yes, a quick check-through is worth the few minutes it takes. Confirm that your catchment pump builds and holds pressure rather than short-cycling, which can indicate a pressure tank problem. Run a hot tap to verify your water heater recovered and is producing hot water at the expected temperature. If you have a UV disinfection system, allow it to run for the manufacturer’s recommended flush period before drinking catchment water. Any pump that trips, a water heater that produces an unusual smell, or a system that will not hold pressure after power returns is worth a professional inspection rather than a wait-and-see approach.
Key Takeaways
- Faucets, drains, and gravity-flush toilets run on water pressure, not electricity. County water homes almost always keep cold water during an outage because the utility maintains line pressure without any power from the home.
- Rainwater catchment systems rely on an electric pump to pressurize the house. When power fails, the pressure tank provides a flush or two before the system goes dry.
- UV disinfection only protects catchment water while it has power. The Hawaii Department of Health recommends treating water as untreated if the UV system has been off during an outage.
- The Department of Energy notes that water heating accounts for about 18 percent of a typical home’s energy use, making plumbing-related equipment one of the larger electrical loads in most homes.
- Gas tank water heaters with standing pilots keep producing hot water through outages. Gas tankless units with electronic ignition and all-electric tankless heaters stop immediately.
- Thermosiphon solar water heaters circulate water by convection without a pump, making them the most outage-resilient option for water heating in Hawaii’s climate.
- Sewage ejector pumps stop during outages. Stop sending wastewater into those fixtures immediately to prevent the holding basin from overflowing.
- All Aloha Plumbing is a licensed and insured Hawaii contractor (License CT-36812) serving Hilo and Kailua-Kona. Request a service visit for pump, water heater, or filtration inspections.
Citations and References
- U.S. Department of Energy, Energy Savers: Tips on Saving Money and Energy at Home: energy.gov Energy Savers guide
- Hawaii Department of Health, Rainwater Catchment: health.hawaii.gov rainwater catchment