EcoSmart Water Heater Not Heating

Common Symptoms

• Cold water from hot taps even after the unit has been running
• Water is slightly warm but not reaching set temperature
• LED indicator is flashing green but no heat is felt
• LED indicator shows no light at all
• SMARTHEAT point-of-use unit produces no heat at a single sink
• Hot water only flows at low-flow fixtures but not at standard-flow fixtures

Most Likely Causes

1. 1

   Incorrect Breaker Sizing or Tripped Breaker (ECO Series)

   The ECO series demands dedicated circuits with specific breaker sizes — ECO 11: 1×40A; ECO 18: 2×40A; ECO 27: 2×40A; ECO 36: 3×40A. An undersized breaker will trip under load or prevent the unit from reaching full heating capacity. Verify the breaker size matches the spec on the unit's data label and that the wire gauge is correct (ECO 27 requires 8 AWG minimum; ECO 36 requires 6 AWG).

2. 2

   Flow Sensor Not Activating (0.3 GPM Minimum)

   EcoSmart ECO units require a minimum of 0.3 gallons per minute of flow to activate the heating elements. Low-flow showerheads rated below 0.5 GPM may not reliably trigger the flow sensor. The LED will flash green (flow detected) but the elements won't energize if flow is below the activation threshold. Test with a higher-flow fixture first.

3. 3

   Failed Heating Element

   EcoSmart ECO units use copper heating elements with a proprietary thread pattern — generic replacement elements do not fit. A failed element will cause the flashing red LED pattern. Elements must be tested for resistance (an open circuit indicates failure) and replaced with genuine EcoSmart brand elements specific to the model number.

4. 4

   Hard Water Scale Buildup on Elements

   In hard water areas, calcium and magnesium scale accumulates on the copper heating elements, reducing heat transfer efficiency and eventually blocking the element bore. Scale buildup also changes the LED blink pattern and can trigger an overheat condition. Annual flushing with food-grade white vinegar is the preventive measure; advanced scale requires element removal and soaking or full element replacement.

5. 5

   SMARTHEAT Internal Flow Switch Failure

   The SMARTHEAT point-of-use units run on a standard 120V outlet and use an internal flow switch to trigger heating. If the flow switch fails internally, the unit will not heat even with adequate flow. Internal flow switch failure typically requires unit replacement as the component is not user-serviceable.

Quick DIY Checks

1. 1Step 1 — Read the LED indicator: locate the LED light on the EcoSmart ECO unit (usually on the front cover). Interpret the pattern: no light = power issue (go to Step 2); solid green = heating element is energized (go to Step 4 to check flow and temperature rise); flashing green = flow detected but elements not heating (low flow — go to Step 3); solid red = overheat trip — press the blue reset button (go to Step 5); flashing red = element failure (go to Step 6). For SMARTHEAT units: if the outlet indicator light is off, check the outlet's GFCI reset first.
2. 2Step 2 — No LED light: verify power to the ECO unit. Go to your electrical panel and locate the dedicated breaker(s) for the water heater. ECO 11: should have 1×40A breaker; ECO 18: 2×40A; ECO 27: 2×40A; ECO 36: 3×40A. A breaker that has tripped will be in the middle position — push it fully to OFF then back to ON. If the breaker trips again immediately under load, the issue is a shorted element (go to Step 6) or undersized wiring. Do NOT repeatedly reset a breaker that immediately trips — call an electrician.
3. 3Step 3 — Flashing green LED (flow detected, no heat): the flow sensor has detected water movement but it is below the 0.3 GPM activation threshold, or the flow is borderline. Test at a standard bathroom lavatory faucet (not a low-flow showerhead) to verify the unit heats at a flow rate above the threshold. If the unit heats at the sink but not at the showerhead, replace the low-flow showerhead with a model rated at 1.5 GPM or higher. If the unit does not heat at any fixture, verify the inlet cold water supply valve is fully open and the inlet filter screen is clear of debris.

1. 4Step 4 — Solid green LED (unit appears to be energized) but water is not hot enough: first, confirm the temperature dial on the unit is set to the desired temperature (most ECO units have a dial with settings from ~80°F to ~140°F). Second, check the incoming cold water temperature — in winter, cold water entering at 40°F requires more heating capacity than summer water at 65°F. The ECO 11 (11kW) can raise 40°F water by approximately 31°F at 1.3 GPM; reducing flow increases temperature rise. If the unit cannot reach target temperature even at reduced flow, proceed to element resistance testing in Step 6 to identify a weak element.
2. 5Step 5 — Solid red LED (overheat trip): press the blue reset button on the unit. The reset button location varies by ECO model — check both the top of the unit and the bottom panel. After pressing the reset: restore power if it was turned off, open a hot tap, and verify the LED returns to solid green and hot water flows. If the overheat trips again quickly, the root cause is either a failed element (causing localized overheating), inadequate flow, or a faulty temperature sensor. Investigate element resistance (Step 6) if the overheat trip repeats.
3. 6Step 6 — Flashing red LED or repeated overheat: element resistance testing. Turn off all dedicated breakers for the ECO unit and allow the unit to cool for 10 minutes. Remove the front cover (typically 4 screws). Locate the copper heating elements — the ECO 27 has 3 elements; the ECO 36 has 4 elements. Disconnect the element wiring leads and test each element with a multimeter set to resistance (ohms). A healthy element will show a finite resistance reading (typically 10–30 ohms depending on model and wattage). An open circuit (OL or infinite resistance) indicates a failed element. Order the correct EcoSmart replacement element for your specific model — the ECO series uses a proprietary thread size and ONLY genuine EcoSmart elements will seal correctly. Do not use generic elements.
4. 7Step 7 — Element replacement (if needed): with breakers off and unit cooled, shut the cold water supply to the unit. Open a hot tap to release pressure. The element is threaded into the heating chamber — use an element wrench (or large socket wrench) to unscrew the element counterclockwise. Inspect the element bore for scale. If significant scale is present, flush the chamber with white vinegar before installing the new element. Install the new EcoSmart element with a fresh O-ring (included in the element kit — do NOT reuse the old O-ring). Hand-tighten then snug 1/4 turn with the wrench. Restore water supply, check for leaks, then restore power.

Repair vs Replace

Recommended Tools & Parts

• EcoSmart Replacement Heating Element (ECO Model-Specific)

  Genuine EcoSmart copper heating element with proprietary thread. Order the element kit specific to your model (e.g., ECO 27 E-01 kit includes element + O-ring). Do NOT use generic elements — they will not seal to the proprietary thread and will leak.

  $80–$150 per element

  Buy on Amazon →

• Digital Multimeter

  Required for testing heating element resistance (open circuit = failed element) and verifying 240V power at the unit's terminal block before and after breaker work.

  $15–$35

  Buy on Amazon →

• Non-Contact Voltage Tester

  Essential safety tool for verifying all 240V power is off before opening the EcoSmart ECO unit. Required before any internal work.

  $15–$30

  Buy on Amazon →

• EcoSmart Inlet Filter Screen

  Replacement inlet filter screen for EcoSmart ECO units. Hard water and sediment can clog the inlet filter and reduce flow below the 0.3 GPM activation threshold.

  $10–$20

  Buy on Amazon →

Links are Amazon affiliate links (tag: fixitfastai-20). Prices are estimates.

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