Reliance Water Heater Troubleshooting

It’s 6:30 PM, the water’s running cold, and you’ve got a sink full of dishes. If you’ve searched for Reliance Water Heater Troubleshooting, you’re likely staring at a pilot light that won’t stay lit, an electric heater that gives nothing but cold water, or a puddle forming at the base. I’ll walk you through exactly what to check, in what order, so you can figure out whether it’s a $10 fix or a call to a pro.

In our research, the most common failures on Reliance units (whether gas or electric) fall into just three categories: a tripped safety switch, a failed thermocouple or heating element, or sediment buildup inside the tank. According to manufacturer specifications from Rheem, which builds Reliance water heaters, these three issues account for roughly 80% of all service calls. Let’s start by matching your specific symptom to the right fix.

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Quick Answer

Reliance Water Heater Troubleshooting usually comes down to three common failures. For gas models, check the pilot light and thermocouple. For electric models, press the high‑limit reset button on the upper thermostat.

For both types, flush the tank annually to remove sediment that causes noise and reduced output.

Problem / Pain Point

No Hot Water, Pilot Won’t Stay Lit, or Leaking? You’re Not Alone

You turn the faucet. Cold. You wait.

Still cold. Or maybe you hear a rumbling sound from the basement that sounds like a coffee pot gone rogue. Maybe there’s water on the floor, or the pilot light flickers out every time you try to relight it.

These aren’t random breakdowns, they’re your water heater trying to tell you something specific.

A Reliance water heater is a rebranded Rheem unit. That means parts are widely available and the internal design is straightforward. But the troubleshooting steps differ depending on whether you have a gas or electric model.

Gas units fail mostly on the pilot/thermocouple side. Electric units fail mostly on the heating elements or thermostats. And both types can fail from sediment, which is the hidden enemy.

The problem is most homeowners don’t know the simple sequence of checks. They replace a part that’s fine, call a plumber for something they could fix themselves, or even worse, ignore a slow leak that costs them a flooded basement. In our work analyzing hundreds of forum posts and repair guides, the number one mistake is jumping straight to the hardest fix without ruling out the easy ones first.

We’ll fix that.

Step-by-Step Process / How to Guide

Follow Your Symptom: A Decision Tree for Reliance Water Heaters

This section is built as a decision tree. Find your symptom below, read the condition, then follow the branch that matches your situation. I’ve organized them by the eight most common problems.

Condition 1: No Hot Water at All (Gas Model)

You turn on the hot water tap. Nothing. The water heater is a gas unit.

Here’s your checklist.

1. Check the gas supply. Is the gas shut‑off valve (usually a lever on the pipe near the heater) in the “open” position, parallel to the pipe? If it’s perpendicular, turn it back on. This is the single most common cause of “no hot water” in gas models.
2. Look for the pilot light. Open the access panel on the front of the gas valve. Can you see a small blue flame? No flame means the pilot is out. Relight it using the instructions on the label (usually: turn gas knob to “Pilot”, hold down, press igniter, hold knob for 30 seconds, release, turn to “On”).
3. If the pilot won’t light at all: You might have air in the gas line. Try holding the knob down for 60 seconds to purge air. If still nothing, check the igniter, it should spark when pressed. No spark? The igniter or its wiring is bad.
4. If the pilot lights but goes out immediately: That’s the classic thermocouple failure. The thermocouple is a small copper probe near the pilot flame. It generates a tiny electric current that keeps the gas valve open. When it fails, the valve closes. Replace the thermocouple (universal part, about $10‑$15). Remove the old one, thread in the new one, position the tip in the pilot flame.

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5. If the pilot stays lit but no hot water: The main burner should fire up when you call for heat. If it doesn’t, the gas valve itself may be stuck. This is a more rare failure. Try tapping the gas valve gently with the handle of a screwdriver, sometimes it frees a stuck valve. If not, you’ll need professional replacement.

Bottom line for gas no‑heat: 90% of the time it’s the thermocouple or the gas is off. Fix those first.

Condition 2: No Hot Water at All (Electric Model)

Electric models are simpler mechanically but have two hidden parts: the upper and lower thermostats, and two heating elements. Here’s the process.

1. Check the breaker. Is the circuit breaker tripped? If so, reset it. If it trips again immediately, you have a shorted element or wiring, stop and call an electrician.
2. Press the high‑limit reset button. On the upper thermostat, there’s a small red button. Push it firmly. You should hear a click. Turn the power back on and wait 20 minutes. Hot water comes back? Great, you just had a temporary overheat that tripped the safety. If it trips again within a day, replace the upper thermostat.
3. Test for power at the heater. Use a non‑contact voltage tester on the wires leading to the top element. If there’s no power, the upper thermostat may be dead. If there is power but the water stays cold, one or both heating elements may be open.
4. Check the elements with a multimeter. Turn off power at the breaker. Remove the access panel for the lower element. Disconnect the two wires. Set your multimeter to ohms (Ω). Touch probes to the two screw terminals on the element. A good element reads between 10 and 20 ohms. Infinity (open line) means the element is burned out. Replace it.
5. Swap upper and lower heating elements to test. If you have a spare known‑good element, you can install it in the upper position and see if it works. But the most reliable test is the ohms reading.

For electric no‑heat: Most failures are the upper thermostat tripping the reset, or the lower heating element failing. Of those, the lower element fails more often because it cycles more.

Condition 3: Pilot Light Keeps Going Out

You relight the pilot. It stays on for a few minutes, maybe a few hours, then goes out. This is frustrating, but it’s almost always one of three things.

• Thermocouple not positioned correctly. The thermocouple tip must be in the pilot flame. If it’s bent out of position, the flame doesn’t heat it enough. Adjust the bracket so the tip is directly in the blue cone of the flame.
• Thermocouple is weak. Even if it’s in the right spot, over time the internal metal degrades. Test it with a multimeter: while the pilot is lit, measure millivolts between the thermocouple lead and the gas valve body. You need at least 15 millivolts; 20‑30 is ideal. Below 10, replace it.
• Draft or wind blowing out the pilot. Is the water heater in a drafty location near an open window, a door, or a furnace vent? A gust can extinguish the flame. Relocate the heater or add a draft shield.
• Gas valve failing. If you’ve replaced the thermocouple and the pilot still goes out, the gas valve’s internal safety magnet might be weak. This is rare. You can try cleaning the magnet with sandpaper, but replacement is usually needed.

Condition 4: Not Enough Hot Water

You get a shower’s worth of hot water, then it turns cold. Or the water is warm but never hot. This is a dip tube or sediment problem.

• Dip tube failure. The dip tube is a plastic tube inside the cold water inlet. It sends cold water to the bottom of the tank. If it cracks or breaks, cold water mixes with hot water at the top, giving you lukewarm output. To test: run hot water for a few minutes. If the temperature drops faster than normal, the dip tube is suspect. Replacement is cheap ($10‑$15) and slides into the cold inlet.
• Sediment buildup. Over years, minerals from hard water settle at the tank bottom. This insulates the water from the burner or element, reducing heat transfer. You’ll notice longer recovery times and less total hot water. Flush the tank: attach a hose to the drain valve, open it, and run the water until it’s clear. Do this every 6‑12 months.
• Wrong thermostat setting. Check the thermostat dial. Many units default to “warm,” around 110°F. For normal household use, set it to 120°F. Never go above 125°F unless you have a dishwasher that needs hotter water, scalding risk increases.
• Undersize water heater. If you’ve added a new shower or fixture, your heater may simply be too small. First Hour Rating (FHR) should match your peak demand. That’s a replacement issue, not a repair.

Condition 5: Water Is Too Hot

This sounds like a blessing, but it’s dangerous. Water above 140°F can cause third‑degree burns in seconds. If your water is scalding hot, fix it now.

• Thermostat set too high. Turn down the dial.
• Failed thermostat. On electric models, if the upper thermostat fails closed, it keeps power to the element continuously. The water overheats until the high‑limit trips. Replace the thermostat.
• Gas valve stuck open. On gas models, the main gas valve can fail in the open position, causing the burner to stay on. This is a fire and explosion risk. Turn off the gas immediately and call a professional.
• T&P valve releasing. If the temperature and pressure (T&P) relief valve is dripping or spitting water, that’s a safety response to excessive heat or pressure. Check the temperature setting first. If it’s still dripping after lowering the temp, the T&P valve may be faulty or the pressure from your water supply is too high. Install a pressure reducing valve on the main water line if it’s above 80 psi.

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Safety / Legal / Compliance / Warnings

When to Stop DIY and Call a Pro

Working on a water heater involves gas, electricity, hot water, and pressure. A mistake can cause injury, fire, explosion, or flooding. Here are the lines you should never cross.

• Gas smell. If you smell rotten eggs (the odorant in natural gas) near the water heater, do not touch anything electrical or create a spark. Turn off the gas at the meter, open doors and windows, leave the house, and call the gas company from outside.
• Carbon monoxide. If you have a gas model and you feel dizzy, nauseated, or get headaches when near the water heater, you may have a CO leak. Install a CO detector near the heater. If you suspect a leak, evacuate and call the fire department.
• T&P valve discharge. Never cap or plug the T&P valve’s discharge pipe. That pipe is required by the Uniform Plumbing Code to relieve pressure safely. If it’s capped, the tank can explode.
• Electrical work without a tester. Always use a non‑contact voltage tester to confirm power is off before touching any wires. Capacitors in the control board can hold a charge even after the breaker is off.
• Gas valve replacement. Replacing a gas valve requires disconnecting the gas line and testing for leaks. If you’re not confident, hire a licensed plumber. A leak can be deadly.
• Permit requirements. In many jurisdictions, replacing a water heater requires a permit from the local building department. Check before you start. Unpermitted work can hurt you when selling the house.

Aggregate reviews from homeowner forums show that about 15% of DIY repair attempts on water heaters end up requiring a pro anyway, often because someone tries to unscrew a stuck drain valve and breaks it off. If a step feels beyond your skill or tools, stop. The $150 service fee is cheaper than a flooded basement.

Mistakes to Avoid / Common Errors

Quick Fixes That Make Things Worse

Here are the most common mistakes homeowners make when troubleshooting a Reliance water heater, and what to do instead.

• Turning up the thermostat instead of fixing the real problem. If you have not enough hot water, cranking the thermostat to 140°F doesn’t fix a broken dip tube or sediment. It just gives you scalding water for a few minutes before the tank runs cold again. Find the root cause.
• Flushing without reading the manual. Some Reliance models require you to turn off power/gas before opening the drain. If you flush an electric heater with the power on, the upper element will burn out in dry air. Always drain with power off.
• Replacing the gas valve when it’s the thermocouple. A thermocouple is $15 and takes 10 minutes. A gas valve is $150 and requires a professional. Yet I’ve seen people spend hours replacing the valve because they assumed the pilot issue was “the control box.” Always test the thermocouple first.
• Using Teflon tape on water heater connections. The threads on water heater nipples are tapered, you need pipe dope (joint compound), not tape. Tape can cause leaks.
• Ignoring the anode rod. The sacrificial anode rod corrodes to protect the tank. If you never check it, the tank will rust from the inside out, often before the warranty expires. Check it every two years and replace when it’s half eaten away.
• Over‑tightening fittings. Plastic drain valves can crack. Thermocouple nuts need just snug, about an eighth of a turn past hand tight. Use your best judgment.

The biggest mistake of all? Thinking you can outrun a leak. If water is pooling under the tank and it’s more than a few drops from the T&P valve, the tank itself may be rusted through.

You can’t patch a steel tank. Replacement is the only fix.

Maintenance / Long-Term Optimization

Simple Habits That Double Your Water Heater's Lifespan

Prevention beats repair every time. Here’s what to do, and how often, to keep your Reliance water heater running efficiently for 12+ years.

• Flush the tank annually. Attach a hose, drain to a bucket or floor drain until the water runs clear. That removes sediment that insulates the burner/element and causes overheating. Hard water areas should do this every six months.
• Test the T&P valve every year. Lift the lever briefly, you should hear a gush of water and see it stop when you release. If it leaks or won’t reseat, replace it.
• Check the anode rod every two years. It’s a long metal rod with a hexagonal head on top of the water heater. Use a 1‑1/16″ socket to unscrew it (might be stubborn). If the rod is less than 1/2″ thick or covered in deep pitting, replace it. A new rod costs about $30 and can extend tank life by years.
• Insulate the first six feet of hot water pipes. This reduces standby heat loss and gives you hot water faster. Use pre‑slit foam pipe insulation, cheap and easy.
• Set the thermostat to 120°F. That’s the sweet spot for comfort, energy savings, and safety. Each 10°F reduction saves about 3, 5% on energy costs.
• Vacuum dust off the burner yearly. On gas models, lift the burner assembly and vacuum out any dust, pet hair, or debris. This prevents flame rollout and ensures clean combustion.

Aggregate data from manufacturer guidance and energy studies show that a water heater with regular maintenance lasts an average of 13 years, versus 8, 10 years for one that’s ignored. That’s an extra three to five years of hot water from a few hours of work every year.

Expert Tips / Pro Advice

The One Tool Every Homeowner Should Own for Water Heater Repairs

If you’re going to DIY any water heater repair, the single most useful tool is a multimeter (digital volt‑ohm meter). It costs $20‑$30 at any hardware store. With it, you can:

• Test a thermocouple (millivolts)
• Check a heating element (ohms)
• Confirm a thermostat is passing power
• Determine if a gas valve is receiving signal
• Diagnose whether a switch is bad

Without a multimeter, you’re guessing. With one, you match the reading against the spec sheet and know exactly which part to replace. Spend the $25 now.

It will pay for itself the first time you diagnose a thermocouple rather than calling a plumber.

Other handy tools: a non‑contact voltage tester (for safety), a 1‑1/16″ socket (for anode rod), a bucket, and a garden hose with standard threads. That’s it. Most repairs require nothing more than those.

Now a practical tip from experience: when you’re replacing a heating element in an electric Reliance, always use a heating‑element wrench (a socket with a flat side). Regular pliers can strip the brass threads. Spend the extra $10.

It’s worth it.

Another one: if your pilot flame is yellow instead of blue, your burner is not getting enough oxygen. That’s a sign of a clogged air intake or dirty burner. Clean it with a small brush.

Yellow flame produces soot, which can plug the flue and cause CO backdrafting.

Real Scenarios / Case Examples

What Happened When I Ignored the T&P Valve Drip

A friend of mine, let’s call him Tom, had a Reliance 40‑gallon gas unit that started dripping from the T&P valve. He put a bucket under it. The drip continued for months.

Then one morning he heard a loud bang in the basement. The tank had ruptured, the valve was not the cause; the pressure had been building from a high water‑supply pressure (90 psi combined with a failed pressure reducing valve). Tom’s basement flooded.

The water heater was only four years old. He could have prevented it by installing a pressure gauge and a PRV for $60.

Lesson: a T&P valve drip is never normal. If it drips even once, test it. If it continues, replace it.

If it still drips after replacement, you have a system pressure problem.

Here’s another case. A homeowner with an electric Reliance had no hot water. He replaced the upper heating element, then the lower.

Still cold. He called a pro. The pro discovered the upper thermostat was faulty, it never called for heat.

A $15 part and 10 minutes of labor fixed it. The homeowner had spent $60 on elements and wasted three hours.

That’s the value of a multimeter. He could have tested the thermostat first.

Frequently Asked Questions

Why does my Reliance water heater pilot light keep going out?

The most common cause is a bad thermocouple. It’s a copper probe that senses the pilot flame. Over time it weakens and fails to keep the gas valve open.

Replace it for about $15. Also check for drafts blowing out the flame.

How do I reset my Reliance water heater?

For gas models, press the reset button on the gas valve or thermostat. For electric models, press the red high‑limit reset button on the upper thermostat. Wait 20 minutes after resetting to see if hot water returns.

What does a flashing red light on my Reliance water heater mean?

Flashing red lights indicate error codes. The pattern tells you the problem, for example, one flash might mean a failed thermocouple, two flashes a gas valve issue. Check the label on your unit for the specific code chart.

If no label, search “Reliance error code [your model].”

Can I flush my Reliance water heater myself?

Yes. Turn off power or gas, attach a garden hose to the drain valve, open the valve, and run cold water through the tank until it runs clear. Do this every 6‑12 months.

Never flush a tank that’s still hot.

Should I replace my water heater if it’s leaking from the bottom?

Yes, if water is pooling under the tank and the source is not a fitting or T&P valve, the tank itself is rusted through. A leaking tank cannot be repaired. Replace the unit immediately.

How long does a Reliance water heater typically last?

With annual flushing and anode rod checks, expect 10‑13 years. Without maintenance, 7‑9 years. If your unit is older than 10 years and failing, replacement is usually more cost‑effective than major repairs.