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IDEALBOILER

Ideal · Boiler

Ideal L1 error code

Overheated or no water flow

Ideal lists L1 as flow temperature overheat or no water flow. The water in the boiler got too hot, or isn't moving through it, so it has stopped.

What to check

Worth repairing?

Worth fixing

Closed valves or low pressure cost nothing to sort. If it keeps happening, an engineer needs to find the cause.

Can you do it yourself?

Easy

About 15 minutes

Before you start

  • Never take the boiler's cover off. Anything inside is a job for a Gas Safe registered engineer.

What to check, in order

  1. Open the radiator valves

    Ideal says to make sure all the radiator valves are open.

  2. Check the pressure

    The gauge should read 1 to 1.5 bar. If it's lower, top it up with the filling loop.

  3. Reset the boiler

    Press the restart button.

When to call a Gas Safe engineer

If that doesn't fix it, contact Ideal, or a Gas Safe registered engineer if the boiler is out of warranty.

Checked against

Last reviewed September 2026. Manufacturers update their pages, and your manual is the final word.

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