Emergency
Fig. 17 on Chaffoteaux Duo

Your boiler is releasing excess water because the internal pressure is too high or the safety valve has been triggered to prevent damage from overheating.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

What the manual says

Manufacturer manual

Discharge from temperature and pressure relief valve

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

Engineer required

This is a emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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 Fig. 17: 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 guides you might find useful

Boiler keeps losing pressure

Six most common causes of dropping pressure.

Read →

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →