Tankless water heater inlet filter screen
Check only after matching the heater model and shutting off water. Low flow can trigger tankless fault symptoms.
$8-$25
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E101 on a State water heater needs a model check before a repair decision. State sells gas tank, electric tank, heat-pump, power-vent, and tankless water heaters, and the same number can mean different things depending on the control platform.
If your display is on a State or A.O. Smith style tankless heater, treat 101 or E101 as a combustion, venting, or air-supply warning until proven otherwise. That is a service-level fault, not a part-swap guess.
Quick Triage
| Heater type | What to do first | Why it matters |
|---|---|---|
| Tankless gas | Check intake, exhaust, gas, flow | 101-style faults can involve combustion |
| Power-vent gas tank | Check blower and vent termination | Vent safety faults need service |
| Electric tank | Compare against the service sheet | E-codes differ by control style |
| Heat-pump hybrid | Check air filter and condensate | Hybrid faults may involve airflow |
| Unknown model | Find rating plate and manual | Do not order parts from code alone |
Safe Reset Order
- Write down the exact display code, including whether it says 101, E101, or another prefix.
- Copy the full model and serial number from the rating plate.
- Turn the heater off for 30 seconds, then power it back on one time.
- Confirm the gas shutoff valve is open if it is a gas or tankless model.
- Check the intake and exhaust terminations outside for leaves, snow, nests, or blocked screens.
- Clean the cold-water inlet filter only if your manual shows the procedure for your model.
- If E101 returns, stop using repeated resets and schedule service.
Do Not Guess at Gas Parts
Do not replace a gas valve, fan, igniter, flame rod, or control board from E101 alone. A tankless combustion warning can come from venting, fuel pressure, air supply, scale, condensate drainage, or a sensor circuit.
If the heater smells like gas, makes a booming ignition sound, or shows soot around the vent, shut it down and call a licensed technician.