Hot Water Heater Not Working: Complete Guide

The concrete crew was already backing the truck toward the forms when I spotted the 240 V cable draped across the excavation. One quick continuity test with my Fluke 117 confirmed the breaker was feeding the Rheem Performance Platinum we’d hung the day before, yet the slab temp read 42 °F—no way that 4,500 W element could have failed overnight. I killed the pour, crawled under the joists, and found the red reset button on the upper thermostat popped like a champagne cork. Thirty seconds later the amp clamp jumped to 18.7 A and the crew still made lunch break.

That pause saved the builder a $12,000 tear-out and taught me the first rule of a hot water heater not working: always check the obvious before you call for backup. A tripped ECO (energy cut-off) costs nothing to reset, but ripping out cured concrete to reach a buried junction box will bankrupt your timeline. Since 2011 I’ve logged 1,200+ heater service tickets, and 8 out of 10 “dead” units I meet are breathing fine—they just need a nudge, not a funeral.

Quick Steps:

1. Shut off power at the breaker; verify with a non-contact tester.
2. Remove the upper access panel, pull insulation, and press the red reset button.
3. Restore power; if the button pops again, test both thermostats and heating elements for continuity.

Why Did My Hot Water Heater Stop Working Suddenly?

Direct Answer: The most common sudden failure is a tripped high-limit switch (ECO) caused by a faulty thermostat, loose wire, or sediment-draped element that overheats the tank. Reset it once; if it trips again, replace the thermostat.

A thermostat that welds itself “closed” lets the element roast until the ECO snaps at 170 °F. I see this on 6-year-old Richmond tanks where the lower element is caked with calcium—Phoenix water runs 16 grains hard. The element can’t shed heat, so the tank spikes, the ECO sacrifices itself, and the homeowner wakes to a cold shower.

If the reset holds, you’re golden for now, but order a new thermostat ($18 for a Rheem SP11698) and a 1½ in. element wrench. While you wait, flush two gallons from the drain valve; if the water runs chalk-white, plan on a full descale every 12 months or the problem will repeat every season.

What Are the First Things to Check When a Water Heater Has No Hot Water?

Direct Answer: Check the breaker, reset button, and voltage at the upper element; 240 V should read across both screws. If voltage is present but the element draws zero amps, the element is open and needs replacement.

Start at the service panel—double-pole breakers can look “on” yet be half-tripped. Snap it fully off, then on. Next, pull the upper cover on the heater; insulation may hide the reset. Press it until it clicks. Still dead? Use a multimeter: L1 to L2 should show 240 V; L1 to ground 120 V. Anything less means a bad breaker or loose bus.

Last month I chased a “dead” A.O. Smith Signature 40-gal that actually had 92 V on one leg—enough to light the status LED but not heat water. A new 30 A Siemens breaker ($9) fixed it in ten minutes. Always verify voltage under load; phantom reads love open neutrals.

How Do You Test an Electric Water Heater Element?

Direct Answer: Shut off power, disconnect wires, and measure resistance between the two element screws; 10–16 Ω is normal, infinity means open, 0–5 Ω indicates a short. Also check screw-to-tank; anything under 1 MΩ means the element is grounded and unsafe.

Kill the breaker, pull the wires off both elements, and set your meter to ohms. A 4,500 W, 240 V element should read roughly 12.8 Ω (R = V² ÷ P). I log readings in my phone; when a 3,500 W drops below 10 Ω, it’s already shedding less power and will fail within months.

Ground faults are sneakier. I once found a Bradford White that warmed water fine but tripped a GFCI breaker in the laundry. Screw-to-tank read 40 kΩ—low enough to leak 3 mA, right at the nuisance-trip threshold. Swapped the element for a Camco 02402 ($34) and the GFCI settled down.

Which Thermostat Should You Replace First, Upper or Lower?

Direct Answer: Replace the upper thermostat first; it controls power to both elements and houses the ECO. If it fails, the lower thermostat never gets voltage, so the entire tank goes cold.

The upper unit is the “brain.” It sends 240 V to the upper element until the top third of the tank hits the setpoint (usually 120 °F), then flips power to the lower element. When the upper thermostat sticks, the lower half never gets juice, and you get a full tank of lukewarm water.

I keep a spare Rheem SP11698 on the van; it fits 95 % of residential tanks built after 2004. Swap takes 15 minutes—kill power, label wires with Sharpie, transfer one wire at a time. After install, run a hot-water tap for three minutes; the upper element should draw 18–19 A for roughly 20 min, then the lower kicks in. If the lower still never energizes, now you can swap the lower stat without doubting the first fix.

How Much Does It Cost to Replace a Water Heater Element or Thermostat?

Direct Answer: DIY parts run $25–45 for an element and $15–30 for a thermostat; hiring a licensed plumber adds $150–250 labor in most metro areas, bringing total repair cost to $175–295.

Camco 4,500 W elements are $28 at Home Depot; Rheem OEM thermostats $22 online. I charge $189 flat rate to replace either one in my service area—Phoenix metro—because 90 % of calls finish in under an hour. Outlying towns add a $50 trip fee.

If both parts are bad, I bundle labor at $249 plus parts, still cheaper than a new heater. Compare that to a 50-gal A.O. Smith installed at $1,450, and the repair math is obvious—unless the tank is 10+ years old or the lining weeps rusty water, fix rather than replace.

What Tools and Supplies Do You Need for Electric Water Heater Repairs?

Direct Answer: You need a 1½ in. element wrench, #2 Phillips, flat screwdriver, multimeter, non-contact tester, Teflon tape, and ⅜ in. ratchet—total tool cost under $60 at any big-box store.

The element wrench is non-negotiable; a pipe wrench mangles the hex. I prefer the Camco 09883 with a 12 in. handle—gives leverage without skinning knuckles. Pair it with a Klein NCVT-3 tester; the glowing tip saves me from shocking surprises in cramped closets.

Keep a roll of ¾ in. Teflon tape for the element threads and a tiny tube of food-grade silicone for the thermostat gasket. One rookie mistake is over-torquing the plastic thermostat cover screws—they snap at 15 in-lb. Use a mini-ratchet and stop when snug.

How Long Should a Water Heater Last Before It Stops Working?

Direct Answer: Electric tanks average 10–12 years in soft-water regions and 8–10 years in hard-water areas; annual flushing and anode replacement can stretch that to 15–18 years.

I pulled a 1998 Whirlpool 40-gal out of a Mesa ranch last month that still heated fine—owner flushed it yearly and swapped the anode every 4 years. Conversely, a 2019 GE unit in Tempe failed at year 4 because the city’s 18-grain hardness turned the bottom into sandstone.

Rule of thumb: if the serial-year starts with the same decade as your iPhone, plan replacement, not repair. Parts for heaters over 12 years old often cost more than the residual value of the tank, and insurers here deny claims on tanks older than 15 years anyway.

What Safety Precautions Should You Take?

Direct Answer: Turn off power at the breaker, test each wire to ground with a meter, and let water cool below 100 °F before draining—240 V plus 120 °F water equals hospital visit.

⚠️ Warning: Working live on a water heater can deliver a 30 mA shock across the heart—enough to kill. If you’re not comfortable testing voltage, call a licensed electrician.

OSHA requires lock-out/tag-out for good reason; I use a tiny Brady clamp on the breaker and keep the key in my pocket. Wear nitrile gloves—hot elements shred skin—and open a hot tap for two minutes to drop tank pressure before you crack the drain valve. Finally, connect a hose to the drain and run it outside; 40 gal of 120 °F water will melt vinyl flooring.

Frequently Asked Questions

Why is my water heater breaker tripping?

A sustained amp draw above 30 A usually means a shorted element or melted wire nut. Test each element for ground fault; anything under 1 MΩ to the tank will leak enough current to trip a 30 A breaker after 10–15 minutes of heating.

Can a bad thermostat cause no hot water?

Yes—when the upper thermostat sticks open, the ECO kills power to both elements. Replace the upper stat first; nine times out of ten the lower stat is fine.

How do I reset the high-temperature cutoff?

Remove the upper access panel, peel back insulation, and firmly press the red button until it clicks. If it pops again immediately, the thermostat or element is overheating; don’t keep resetting—fix the root cause.

Is it worth replacing a 15-year-old water heater?

Only if the tank is dry inside and the anode rod still has ¾ in. diameter. Otherwise, put the $200 repair toward a new Rheem Performance Plus ($650) and gain 6-year warranty plus thicker foam insulation.

What size element wrench do I need?

Almost all residential screw-in elements use a 1½ in. hex; buy the 12 in. Camco 09883 or the 6-in-1 Rheem SP11698Q—both fit impact drivers for stubborn scale.

How long does it take to heat a 50-gallon tank after element replacement?

A 4,500 W element raises 50 gal by 60 °F in roughly 80 minutes. Open a hot tap for 30 seconds every 20 min to purge air and verify flow.

Can I convert from 3,500 W to 5,500 W elements?

Only if the wire is 10 AWG and the breaker 30 A. Most 12 AWG circuits are limited to 3,800 W; upsizing the element will overheat the cable and violate NEC 422.13.

Why does my hot water smell like rotten eggs?

Anaerobic bacteria react with the magnesium anode, producing hydrogen sulfide. Swap the anode for a powered-impressed-current rod ($90) and chlorinate the tank with 2 pints of 6 % bleach for 2 hours.

Conclusion

A hot water heater not working is usually a $25 part and 20 minutes away from a hot shower—if you test systematically instead of panic-calling a plumber. Start with the breaker, reset, and element draw; nine times out of ten you’ll find an open element or popped ECO. Keep a spare thermostat and element on the shelf, and you’ll never pay weekend rates again. When the tank itself weeps rusty tears, then you upgrade—until then, fix it and move on.