Medium
P11 on Ferroli Leb TS

Your boiler has detected trapped air bubbles moving through your heating pipes, which is preventing the system from circulating water effectively.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Air release in CH return pipe

From this model's manual
Verified against the Ferroli Leb Ts installation & service manual, page 9.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Check your boiler's pressure gauge to ensure it is between 1 and 1.5 barTop up the system pressure using the filling loop if it is below 1 barBleed all radiators in the house starting from the ground floor and moving upwards to release trapped air

Find a Gas Safe engineer
Search the official register →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like P11: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Related fault codes

P12View →F37View →

Related guides you might find useful

Boiler keeps losing pressure

Six most common causes of dropping pressure.

Read →

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →