E1 or E2 error code appears on the display during the ignition sequence.
Error code E1 or E2 (for the 26L model), as well as code E2 (for the 14L model), generally indicate a problem related to the gas supply.
Possible causes include: an empty gas tank, a blocked gas line or inlet, or insufficient gas pressure.
In some cases, inadequate water flow or pressure may also trigger these error codes.
Please refer to the possible solutions listed below:
- First, ensure that the gas source is not empty, that the gas valves are fully open, and that there are no obstructions in the gas line or at the gas inlet of the water heater.
- Make sure to use a gas line with the appropriate diameter and length based on the number of appliances connected to the same line, as these factors can impact the proper operation of the unit and may cause error codes E1 or E2. (Click on the links below and refer to the tables for recommended gas line sizing.)
Onsen 14L gas pipe size table
Onsen 26L gas pipe size table - Gradually adjust the gas pressure toward the upper limit of the recommended values — 13 inches of water column for propane and 10.5 inches for natural gas — to ensure sufficient pressure for the proper functioning of the unit.
Perform the following checks to determine whether the issue is due to insufficient water flow or pressure, or a restriction in the plumbing:
- First, make sure your water heater is supplied by a water pressure system that meets the minimum requirements for proper operation. The Onsen 14L and 26L models require a minimum stable flow rate of 0.67 gallons per minute and a constant pressure of at least 15 PSI.
- Open all water outlets and observe whether the error code reappears. If no code appears in this situation, but it does show up when only one faucet is open, this likely indicates a restriction in that faucet’s plumbing.
- Run water directly from the heater’s outlet fitting (e.g., into a bucket) to isolate the plumbing downstream of the unit. If the unit functions normally and no error code is displayed, this strongly suggests a restriction in the hot water plumbing — that is, after the water exits the heater.
- Remove the aerators from the sink faucets (if present), then open the faucet(s) again to check if the error still appears.
- Avoid using very low-flow faucets. The Onsen 14L and 26L models require a minimum flow rate of 0.67 gallons per minute to operate properly. Make sure the water heater is only connected to fixtures that provide sufficient flow to prevent error codes E1 or E2 from appearing.