Chapter 5
Generators, well pumps and the transfer switch
The questionHow do I run my well pump on a generator without poisoning anyone or frying the line?
The short answerA generator can run a well pump safely only through a transfer switch installed by a licensed electrician, with the generator outdoors at least 20 feet from doors, windows and vents.
By the editors of High Water at Home · Updated · about 6 minutes
Sections in this chapter
5.1 Where can a portable generator run safely?
Outdoors only, and well away from the house. The CDC's carbon monoxide page, updated 26 Oct 2026, says to use generators outside, more than 20 feet from any window, door or vent, and never inside a home or garage even with the doors open. The Consumer Product Safety Commission adds basements, crawl spaces, sheds and porches to that list, and the CDC adds carports for any gasoline engine used in flood cleanup (Table 5.1).
| Agency | Distance | Never run it in |
|---|---|---|
| CDC (updated 26 Oct 2026) | More than 20 ft from windows, doors and vents | A home or garage, even with doors open |
| Ready.gov (updated 4 Jun 2026) | At least 20 ft from windows, doors and attached garages | Indoors |
| CPSC (release of 27 Aug 2021) | At least 20 ft from the house, exhaust pointed away | Home, garage, basement, crawl space, shed, porch |
| CDC flood reentry (updated 24 Aug 2026) | At least 20 ft from any door, window or vent | Home, basement, garage, carport, porch |
Keep the generator dry and let it cool before you refuel it. Ready.gov warns that touching a wet generator, or anything plugged into one, can shock you. The CDC suggests a heavy extension cord more than 20 feet long so the machine can sit at a safe distance.
5.2 Why is carbon monoxide so dangerous after a storm?
You cannot see or smell it, and it builds up fast in closed or half-closed spaces. The CDC counts more than 400 Americans killed each year by carbon monoxide not linked to fires, more than 100,000 emergency visits and more than 14,000 hospital stays. CPSC estimates about 78 people die each year from portable generator exhaust alone.
Texas has its own count. The state health department's report on the February 2021 storm, dated 31 Dec 2021, found 19 of the 246 storm deaths were carbon monoxide poisonings from generators, grills, heaters, cars in closed spaces and iced-over vents.
5.3 Which carbon monoxide alarms help?
Battery-powered or battery-backup alarms, because the power is what you have lost. The CDC says to put one near every sleeping area; Ready.gov says one on every level of the home. Check the batteries each spring and fall, and replace the alarm when its maker says to or every 5 years.
5.4 How should a generator connect to the well pump?
Through a transfer switch, put in by a licensed electrician, and no other way. The CDC's flood reentry page says it is against the law and a code violation to connect a generator to house circuits without approved automatic-interrupt devices. Never plug a generator into a wall or dryer outlet. That "backfeed" sends power out through your meter onto the street lines.
FEMA's utility guide, P-348 (February 2017), explains why. Power fed backward at 120/240 volts can be stepped up to 12,000 volts or more at the pole transformer, enough to kill a line worker instantly. The same guide describes automatic and manual transfer switches and a small standby panel that usually carries the refrigerator, freezer, well pump, water heater and a few lights and outlets.
5.5 What should you do with the well before you leave?
AgriLife's September 2019 guide to readying a well for floods (ESC-058) says to top up the pressure tank first, then turn off electricity to the well. That stored water gives you some supply after the pump stops. Shut off the well's power only if its breaker or switch sits on dry ground and you are dry; if not, leave it for the electric utility or a licensed electrician. The same guide says to cut power to an aerobic septic unit, with the same condition, as the septic chapter explains.
Cover and secure the exposed parts of the well, too. The wellhead chapter covers the cap and casing.
5.6 What if the pump or its controls went under water?
Leave it off. The EPA's post-flood guide for wells, updated October 2024, warns that switching on a pump that has been under water can shock you and can wreck the pump or the well. The wiring needs a check first by a qualified electrician or a well or pump contractor, and a control box that sat under water has to dry out completely. The EPA adds that rubber boots and gloves do not protect you from shock.
The generator does not change that rule. Powering a soaked control box from a generator is as risky as powering it from the line. The chapter on well pumps and pressure tanks covers the inspection, and the chapter on power that stays off covers the rest of the house.
Questions readers ask
Can the generator run in the carport if both ends are open?
No. The CDC lists carports among the partly enclosed spaces where a gasoline engine must never run. Keep it in the open, more than 20 feet from the house.
Is a cord through a window safe if the generator is far away?
The CDC suggests a long cord so the generator can stay at a safe distance, but an open window lets exhaust drift in. Run the cord so windows and doors can stay shut, and keep a battery CO alarm working inside.
Will a transfer switch run the whole house?
That depends on the generator and the panel the electrician sets up. FEMA's guide describes a standby panel that leaves out large loads such as the range, air conditioner and dryer so a smaller unit can carry the essentials.
Does a CO alarm make it safe to run the generator closer to the house?
No. The alarm is a backup, not a substitute for distance. The CDC's 20-foot rule and the alarm work together.
Does a transfer switch need a permit?
Electrical work in the City of Wharton follows the city's adopted electrical code and permit process, and the county has its own permit office outside city limits. A licensed electrician knows which applies to your address.
What this chapter rests on
The distance and alarm rules come from CDC, Ready.gov and CPSC pages dated 2021 to 2026; the backfeed and transfer-switch material comes from FEMA P-348 (2017); the well steps come from AgriLife's 2019 guide and EPA's 2024 update. No primary source gave a typical well-pump power figure, so none appears here. Texas electrician licensing rules sit outside this chapter; confirm the electrician holds a current state license.
Notes to chapter 5
- CDC — Carbon Monoxide Poisoning Basics · 20-foot rule, death and hospital counts, detector placement and replacement · checked 11 Nov 2026
- CDC — What to Do to Protect Yourself During a Power Outage · extension cord length, symptoms · checked 11 Nov 2026
- Ready.gov — Power Outages · distance from attached garages, wet generator shock, refueling · checked 11 Nov 2026
- CPSC — Protect Your Family Before and After Hurricane Ida (27 Aug 2021) · places never to run a generator, yearly deaths, alarm response · checked 11 Nov 2026
- CDC — Safety Guidelines: Reentering Your Flooded Home · automatic-interrupt devices, carports and porches · checked 11 Nov 2026
- FEMA — P-348, Protecting Building Utility Systems From Flood Damage (Feb 2017) · backfeed voltage, transfer switches, standby panel loads · checked 11 Nov 2026
- Texas DSHS — February 2021 Winter Storm-Related Deaths (31 Dec 2021) · carbon monoxide deaths in the 2021 storm · checked 11 Nov 2026
- Texas A&M AgriLife Extension / TWON — ESC-058 · pressure tank, well power before evacuating · checked 11 Nov 2026
- US EPA — What to Do After the Flood (816-F-05-021) · do not turn on a flooded pump, wiring check, boots and gloves · checked 11 Nov 2026