No Hot Water — Diagnosing & Fixing the Problem

Waking up to no hot water is miserable. The cause depends on whether you have a tank or tankless water heater, and whether the problem is gas or electric. Here's how to diagnose and fix it.

Tank Water Heater — No Hot Water

Gas tank water heater:

• Pilot light is out — the most common cause. Look through the sight glass at the bottom of the unit. No flame means the pilot is out. Follow the relight instructions on the label. If it won't stay lit, the thermocouple needs replacement.
• Gas supply issue — check that other gas appliances in the home are working. If not, contact SoCal Gas.
• Faulty gas valve — if the pilot lights but the main burner won't fire, the gas valve may have failed.

Electric tank water heater:

• Tripped reset button — the most common cause. Find the access panel (usually upper panel), press the red reset button firmly. If it trips again immediately, the element is shorted.
• Failed heating element — upper element failure means no hot water at all. Lower element failure means water runs cold quickly.
• Tripped breaker — check your electrical panel for a tripped breaker on the water heater circuit.

Tankless Water Heater — No Hot Water

Tankless units are more complex. Common causes of no hot water:

• Error code displayed — check the unit's display. An error code (Navien code 3, Rinnai code 11, etc.) points to the specific cause. See our error code guides or call us for diagnosis.
• Flow rate too low — tankless units require minimum flow to activate (typically 0.5 GPM). A partially closed valve or low-flow fixture can prevent the unit from firing.
• Inlet filter clogged — most tankless units have an inlet filter screen that can clog with sediment. A clogged filter reduces flow below the activation threshold.
• Ignition failure — if you hear clicking but no ignition, the igniter or gas valve is the likely culprit.
• Venting issue — a blocked vent prevents the unit from firing and triggers a shutdown.

When To Call a Professional

Call Simple Water Heater & Filtration if:

• The pilot won't stay lit after relighting
• The reset button trips repeatedly
• Your tankless unit displays an error code
• You smell gas near the unit
• The unit is more than 10 years old and this is the first failure

We offer prompt no-hot-water service throughout Los Angeles and the San Fernando Valley. Most causes of no hot water are diagnosed and resolved in a single visit.

Frequently Asked Questions