Ariston 104 Fault

Ariston 104 Fault

The Ariston error code 104 indicates a low water pressure fault in the boiler system. This error arises when the water pressure within the central heating system drops below the minimum required threshold, affecting the boiler’s ability to operate efficiently and safely.

Causes of Error Code 104

  1. Leaks in the Heating System: Any leaks, no matter how minor, can lead to a gradual loss of water and thus a drop in system pressure.
  2. Recently Bled Radiators: Bleeding radiators to remove trapped air can also reduce the overall system pressure if not topped up afterward.
  3. Faulty Pressure Relief Valve: A malfunctioning pressure relief valve can allow water to escape the system, leading to pressure loss.
  4. Natural Pressure Loss Over Time: It’s normal for heating systems to lose pressure over time, necessitating occasional topping up.

Troubleshooting and Resolving Error Code 104

  1. Check for Visible Leaks: Inspect your radiators, pipes, and boiler for any signs of leaks. If you find a leak, it will need to be repaired.
  2. Repressurize the System: You can usually repressurize your boiler system yourself by using the filling loop. The process involves opening the valves on the filling loop to allow water into the system until the pressure gauge reaches the recommended level (typically around 1-1.5 bar), then closing the valves. Instructions for this process should be in your boiler’s manual.
  3. Bleed Radiators: If you haven’t recently bled your radiators, trapped air in the system could be causing pressure issues. After bleeding any air from the radiators, you may need to repressurize the system.
  4. Check the Pressure Relief Valve: If you suspect the pressure relief valve is faulty (e.g., if there’s constant dripping from the discharge pipe), it’s advisable to contact a professional for repair or replacement.
  5. Reset the Boiler: After addressing the low pressure issue, reset the boiler to clear the error code and check if the boiler returns to normal operation.


The Ariston error code 104 is a common issue that often can be resolved by repressurizing the boiler system and checking for leaks. Regular monitoring of your boiler’s pressure gauge can help you catch and address low pressure before it becomes a more significant problem. For persistent issues, professional diagnosis and repair are recommended to ensure your heating system remains safe and efficient.