Cold water at every tap means the heater has stopped producing, not that it is producing too little. That distinction narrows the cause considerably.
No hot water at all is a different fault from water that runs lukewarm, and the difference tells us where to look. SAVA HVAC & Appliance Repair has serviced tank and tankless water heaters across Chicago and the North Shore since 2017. On a gas heater, a complete loss of hot water usually means the burner has stopped firing — most often a failed thermocouple, a pilot that will not hold, or a gas control valve that has quit. On an electric heater it is almost always a burned-out upper heating element or a tripped high-limit reset, and occasionally a tripped breaker. On a tankless unit the control board logs an error code that points to the specific component, which is why we ask for it when you call. SAVA is family-owned, EPA Section 608 Certified, and rated 4.9 stars across 150+ reviews on Google, Yelp and Thumbtack.
The thermocouple is a safety device that senses whether the pilot flame is actually burning. If it detects no flame it closes the gas valve, because releasing gas with nothing to ignite it would be far worse. Thermocouples degrade with age and are one of the most common reasons a gas water heater stops producing entirely. The symptom is usually a pilot that lights and then goes out again shortly afterward.
Electric heaters have two elements, upper and lower. When the upper element fails you get no hot water at all, because it heats the top of the tank where the outlet draws from. Elements are consumable parts, and sediment accelerates their failure by insulating them and forcing them to run hotter than designed.
Every electric water heater has a high-limit switch — often called the ECO — that cuts power if the water exceeds a safe temperature. Once it trips there is no heating at all. The switch itself is rarely the problem; it trips because a thermostat or element has failed, and resetting it without finding that fault simply means it trips again.
The gas control valve houses the thermostat and regulates gas to the burner. When it fails the pilot may light normally while the main burner never ignites, so the tank slowly goes cold even though the unit appears to be working.
A gas water heater has to vent combustion gases safely. If the flue is obstructed, the unit's safety system shuts down the burner rather than allowing exhaust to spill into the room. This is a safety shutdown doing its job, and the obstruction is the actual fault.
Tankless units do not store hot water — they heat on demand. When one stops producing it logs an error code identifying the component: flow sensor, igniter, heat exchanger, or control board. That code is the fastest route to a diagnosis, which is why we ask for it when you call.
The more you can describe, the better the chance we arrive with the right part already on the truck. It helps to know:
Water heaters rarely recover on their own, and the failure modes get more expensive the longer they run. A tank that is corroding ends in a leak, sediment that is left in place shortens the life of the unit, and a safety device that keeps shutting the heater down is reporting a fault that has not been fixed.
SAVA is a family-owned, EPA Section 608 Certified company serving Chicago and the North Shore suburbs since 2017. We service gas, electric, and tankless water heaters, identify the exact fault before any work begins, explain what we found and what it will cost, and give straight repair-versus-replace guidance on older tanks. Learn more about our water heater repair service.
Plus most other residential tank and tankless water heater brands — if yours isn't on the list, call and we'll confirm.
Same-day service when available · Gas, electric & tankless · Chicago & North Shore
Same-day service available · $79 diagnostic — credited toward your repair · EPA Certified & insured