Boiler shows E10, low water pressure or lack of water in system

Safety: Allow the boiler to cool before adding water. Overfilling a hot system can cause thermal stress.

• Step 1 – Read pressure gauge: Check the boiler’s pressure gauge. If below the recommended cold fill (often around 12 psi), the system needs water.
• Step 2 – Use the fill valve: Locate the automatic fill (pressure reducing) valve and manual bypass lever. Slowly open the manual fill or bypass to add water while watching the gauge. Close the valve when the pressure reaches the target.
• Step 3 – Check for leaks: Inspect around the Triangle Tube boiler, relief valve discharge pipe, and visible piping/radiators for signs of water leakage. Repair leaks before refilling repeatedly.
• Step 4 – Reset boiler: Once pressure is restored, reset the boiler. If E10 persists with correct pressure, the pressure sensor or low water cutoff may be faulty.
• Professional service: A technician should test and replace the pressure sensor or low water cutoff and verify the expansion tank and fill valve are working correctly.