Emergency
75 mm on Malvern TenTwenty

Your boiler is reporting a physical blockage or debris issue in the flue or drainage pipes, which is preventing it from venting exhaust gases safely.

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

Below gutter or pipes

From this model's manual
Verified against the Malvern/Malvern Tentwenty installation & service manual, page 5.
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 75 mm: 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

76 mmView →77 mmView →

All 21 fault codes on the TenTwenty

Seeing a different code? Every code this model can display, in one place.

0.51.01.51214161820222426200 mm300300 mm600 mm1200 mm1500 mmLockout lamp illuminating (Overheat Thermostat)Phase reversed neon (behind the knob) lightingRunning lamp flashing

Related guides you might find useful

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →

Frozen condensate pipe

Winter cause of ignition lockouts.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →