There's no worse way to start a morning than stepping into a cold shower. Your water heater picked today to quit, and now you're standing there in a towel wondering if this is a $20 fix or a $2,000 problem. Good news: sometimes it's something simple you can check yourself before spending money on a service call.
We're going to walk you through the most common reasons a water heater stops working and what you can realistically do about each one. Some of these are genuine DIY fixes. Others are "call a plumber" situations, and we'll be straight with you about which is which.
First Things First: What Type of Water Heater Do You Have?
Before you start troubleshooting, you need to know what you're working with. The two main types in San Diego homes are gas and electric tank water heaters. There's also tankless (both gas and electric), but those are a different animal.
Gas water heaters have a burner at the bottom and a vent pipe (flue) going up through the top or out the side. You'll see a gas line connected to it. Most homes in Mira Mesa, Tierrasanta, and throughout the city have gas water heaters.
Electric water heaters have no flue or gas line — just electrical wiring going into the unit and usually two access panels on the front for the heating elements. They're less common in San Diego but definitely out there, especially in condos and some newer construction.
Gas Water Heater: Check the Pilot Light
If you have a gas water heater and suddenly have no hot water, the pilot light is the first thing to check. The pilot light is a small flame that stays lit constantly and ignites the main burner when heat is needed.
Most newer water heaters (made in the last 15 years) have a sealed combustion chamber, so you can't actually see the pilot light. But there's usually a small viewing window near the bottom. Look through it — do you see a small blue flame? If not, your pilot is out.
Relighting the pilot is usually straightforward. There's a knob on the gas valve with settings like "Off," "Pilot," and "On." The instructions are literally printed on the water heater. Turn the knob to Pilot, press and hold it down, and use the built-in igniter (a button or spark striker) to light it. Hold the knob down for 30-60 seconds, then release. If the flame stays lit, turn the knob to On. Done.
If the pilot won't light or won't stay lit, you might have a faulty thermocouple (the safety sensor that detects the pilot flame). That's a $15 part but a repair best left to a professional because you're working with gas. If you smell gas at any point, stop what you're doing, leave the house, and call your gas company immediately.
Electric Water Heater: Check the Breaker
For electric water heaters, the equivalent of a pilot light check is your electrical panel. Find your breaker box and look for the breaker labeled "Water Heater" (it's usually a double breaker, meaning it takes up two slots). Is it tripped?
A tripped breaker sits in a middle position between On and Off. To reset it, flip it fully to Off first, then back to On. If it trips again immediately, don't keep resetting it — there's a short or a bad element, and you need a plumber or electrician.
If the breaker was tripped and stays on after resetting, give the water heater an hour or so to heat up. Tank water heaters in the 40-50 gallon range take roughly 45-60 minutes to recover to full temperature.
If the breaker wasn't tripped and you still have no hot water, the issue is likely a failed heating element or a bad thermostat inside the unit. Electric water heaters have two of each (upper and lower). These are replaceable parts, but the repair involves working inside an electrical panel at 240 volts — not a DIY job unless you're experienced with electrical work.
Check the Thermostat Setting
This one sounds almost too simple, but we've been on service calls in Rancho Bernardo and Del Mar where someone accidentally bumped the temperature dial on their water heater. Maybe you had work done in the garage and the contractor leaned against it, or a kid turned the knob while playing.
For gas water heaters, the temperature dial is on the gas valve near the bottom. It should be set to about 120 degrees or to the "warm" or "B" setting (different brands mark it differently).
For electric water heaters, the thermostats are behind two access panels on the front of the tank. You'll need a screwdriver to remove the panels and a flathead to adjust the thermostat. But again, 120 degrees is the sweet spot for safety and efficiency.
If your water is lukewarm rather than cold, a thermostat issue or a failing lower heating element (on electric heaters) is a common culprit. You're getting some heat, just not enough.
Listen for Strange Sounds
A healthy water heater should be basically silent. If yours is making noise, the sounds themselves can tell you what's wrong.
Popping or rumbling sounds mean sediment has built up at the bottom of the tank. This is extremely common in San Diego due to our hard water. The sediment traps water underneath it, and when the burner fires, that trapped water boils and pops through the sediment layer. A professional flush can sometimes fix this, but if the buildup is severe, the tank may be on its last legs.
Hissing near the bottom of a gas water heater could mean a leak is dripping onto the burner. Check for water pooling around the base of the unit.
High-pitched whining or screaming from an electric water heater usually points to a failing heating element with scale buildup on it. The element is trying to heat through a thick coat of mineral deposits and struggling.
Banging or "water hammer" sounds when you turn hot water on or off are usually a pipe issue, not a water heater issue, but they're worth mentioning to your plumber.
Look for Leaks
Walk around your water heater and look for any signs of water. Check the top first — sometimes what looks like a water heater leak is actually a dripping fitting on the cold water inlet or hot water outlet pipes coming into the top of the tank.
If water is coming from the T&P (temperature and pressure) relief valve — a valve on the side with a discharge pipe running down toward the floor — that can mean the tank is overheating or the valve is failing. Either way, don't ignore it. The T&P valve is a critical safety device.
If water is leaking from the bottom of the tank itself, that's usually game over. The inner tank has corroded through, and no repair can fix it. You need a new water heater. Time to check out our water heater repair and replacement options.
A water heater leaking onto the floor can cause serious damage fast, especially if it's in a closet or on a second floor. If you see active leaking, turn off the gas or electricity to the unit and shut off the cold water inlet valve (the valve on the pipe going into the top of the tank) to stop the flow.
How Old Is Your Water Heater?
If your water heater is acting up and it's 8-12 years old, it might be time to think about replacement rather than repair. The average tank water heater lasts 8-12 years nationally, and with San Diego's hard water, many don't make it past 8.
Not sure how old yours is? Look at the serial number on the rating plate (usually on the side of the unit). Most manufacturers encode the date in the serial number. For example, a serial starting with "2018" or with a letter-number combo like "J18" typically means it was made in 2018. You can also Google the manufacturer name plus "serial number decoder" to figure it out.
If a repair on an old water heater is going to cost $300 or more, we usually recommend putting that money toward a new unit instead. You'll get a more efficient heater with a new warranty rather than sinking money into an aging tank that's going to have another problem in six months.
When to Call a Plumber
You've checked the pilot light, the breaker, and the thermostat. You've looked for leaks and listened for sounds. Here's when it's time to call for backup.
Call a plumber if the pilot won't stay lit (thermocouple or gas valve issue), if the breaker keeps tripping (electrical fault), if you see active leaking from the tank, if the unit is making loud rumbling or popping sounds, or if the hot water is rusty or smells like rotten eggs (sulfur).
Also call if you're just not comfortable doing any of this yourself. There's no shame in that — you're dealing with gas, electricity, and pressurized hot water. These aren't things to mess around with if you're unsure. We offer general plumbing service calls for exactly this situation, and there's no judgment if it turns out to be something simple.
Still can't figure out what's wrong with your water heater? No worries — that's what we're here for. We'll diagnose the problem and give you honest options, whether it's a $150 repair or time for a new unit. Call Pipe Dream Plumbing Co. at (858) 215-1199 or request a free quote.