Quick answer
Check the basics first: the power or gas supply, the thermostat setting, the reset button on electric heaters, the pilot on gas heaters, and any leaks around the tank. Sediment and a failed heating element or burner are other common causes. If you smell gas, leave and call 911. Do not cap or plug the relief valve.
Safety first
Water heaters combine electricity or gas with hot water under pressure. Read these points before you open anything.
If you smell gas, do not investigate. Gas utilities say to leave the area immediately, call your gas utility or 911 from outside, and avoid anything that could create a spark, including flipping switches. PSE adds a sulfur, or rotten egg, odor to natural gas. Pyper Plumbing does not work on gas lines, so a gas smell is a call to your gas utility and 911, not to us.
- Turn off power at the breaker before removing any access panel on an electric heater.
- Never test a live element or thermostat unless you are trained to. Contact with live wiring can cause electric shock.
- Do not cap, plug or close off the discharge pipe of the temperature and pressure relief valve.
- Treat hot water as a burn risk. The CPSC recommends a water heater setting of 120 degrees Fahrenheit.
Know which type of heater you have
A storage tank heater keeps a tank of water hot and is powered by electricity or gas. A tankless heater heats water as it flows and has no tank. The checks differ, so look at the label and the manual first.
A gas heater has a flue and either a pilot light or electronic ignition. An electric tank heater has access panels on the side of the tank covering the thermostats and elements. Montana State University Extension notes that electric heaters have an upper and a lower thermostat.
Step 1: Check power and supply
Start with the simple things that cost nothing.
- Electric tank: check the circuit breaker. A tripped breaker is a common reason for no hot water.
- Gas tank: confirm the gas supply valve to the heater is open and the pilot or ignition is working. If the pilot is out, follow the manufacturer's relighting instructions printed on the tank.
- Tankless: confirm the unit has power and that the gas and water supply valves are open, as Noritz advises.
- All types: confirm the cold water supply valve to the heater is fully open.
Step 2: The reset button and thermostat
A. O. Smith's service training notes that an electric heater's energy cut-off can trip when the tank overheats. Pressing the red reset button restores power if it has tripped, and a click indicates it tripped. Turn power off at the breaker before opening the panel.
If the reset trips again, something is wrong: a failed thermostat, a shorted element or wiring trouble. Repeated resetting is not a fix. A. O. Smith's guide lists upper heating element failure, upper thermostat failure and shorted elements as typical causes, and those tests involve live electrical readings that are best left to a professional.
Also check the setting. Montana State University Extension notes that both thermostats on an electric tank must be adjusted, so a setting that is too low can leave you short of hot water.
Gas pilot light cautions
Montana State University Extension gives these pilot guidelines for gas storage heaters. Turn the gas control to OFF and wait 5 minutes before relighting so any gas in the combustion chamber can clear. Hold the indicator knob for one minute after the pilot lights.
If the pilot will not stay lit, the thermocouple may be faulty or misplaced. The thermocouple is a safety cutoff that shuts the gas off if the pilot goes out. If it still will not light after a second careful try, stop. Do not keep retrying, and if you smell gas at any point, leave the building and call 911 or your gas utility.
Sediment and scale
Sediment and scale reduce heating element efficiency and tank capacity, according to Montana State University Extension. Over time that can mean less usable hot water.
The extension guide describes draining a few gallons from the drain valve near the bottom of the tank into a bucket until the water runs clear, and notes that how often to flush depends on water hardness. If the valve has not been opened in years, it may be hard to close again, so attach a hose first. Remember that the water coming out is hot. Let the tank cool or use extreme care.
For tankless units, Noritz recommends flushing and descaling annually, and says mineral scale can cause temperature problems and low pressure.
Element or burner failure
On an electric tank, a failed upper or lower heating element is a frequent reason for little or no hot water. On a gas tank, a faulty thermocouple or an ignition problem can stop heating, and Noritz lists ignition failures among the reasons to call a professional for tankless units.
These are diagnosis points, not DIY invitations. Testing elements and thermostats requires live electrical readings, and burner and gas control work involves gas. The useful thing you can do is note what you saw: whether the breaker tripped, whether the pilot is lit, any error code on a tankless display, and when the problem started.
Look for leaks and the relief valve
Check around the base of the tank, the supply connections and the discharge pipe from the temperature and pressure (T&P) relief valve. A leak that appears along with no hot water needs a professional look, because it may be the tank or a fitting. A. O. Smith lists a leak on the hot water side of the plumbing as a possible cause of no hot water.
The International Code Council notes that if the heater works properly, system pressure is within code limits and the valve is in good condition, the relief valve should not discharge. Any discharge points to a problem with the distribution system, the heater or the valve. The discharge pipe may carry hot water and steam, so keep clear of it. Its end should never be capped, threaded or valved, because a closed relief path can lead to severe damage, injury or death.
When to call Pyper Plumbing
Call if the heater is leaking, the relief valve is discharging, a reset trips repeatedly, the pilot will not stay lit after one careful try, a tankless unit shows an error code that returns, or you simply do not want to open an electrical panel.
Pyper Plumbing services water heaters across Snohomish, Skagit, Whatcom and Island counties. If water is pooling, shut off the cold water supply to the heater and turn off power at the breaker if it is safe to reach. For a gas smell, leave first and call 911 or your gas utility, then call us once the area is cleared.
Common questions
Why did my electric water heater suddenly stop making hot water?
Common causes include a tripped breaker, a tripped energy cut-off (reset button), a failed thermostat or a failed heating element. Turn power off before opening any panel, and call a professional if the reset trips again.
What temperature should my water heater be set to?
The U.S. Consumer Product Safety Commission recommends 120 degrees Fahrenheit to reduce tap water scalds. Washington DSHS notes that 140 degree water can scald in about one second, while 120 degree water takes about four minutes.
Is it safe to relight a pilot light myself?
Only if you follow the manufacturer's instructions exactly, including waiting 5 minutes after turning the gas control to OFF. If you smell gas or the pilot will not stay lit, stop and call a professional or your gas utility.
Why is my water heater's relief valve dripping?
Per the ICC, a properly working system should not discharge from the valve. Dripping points to a problem with the system pressure, the heater or the valve. Never cap the discharge pipe, and have it checked.
Sources
Facts in this guide come from the following references. Local rules and manufacturer instructions can differ, so follow your utility and your equipment manual.
- Detect a Gas Leak (Puget Sound Energy)
- Water Heater Maintenance (Montana State University Extension)
- No Hot Water, Electric Models (A. O. Smith University)
- Tap Water Scalds (U.S. Consumer Product Safety Commission)
- How Hot is Your Water? (Washington DSHS)
- Water Heater Safety CodeNotes (International Code Council)
- How to Troubleshoot a Tankless Water Heater (Noritz)
This guide is general information, not a substitute for an on-site inspection. If you smell natural gas, leave the building and call 911 or your gas utility. Pyper does not perform gas line work.
