127 Low

Navien 127 Fault Code

The Navien 127 fault code means: your boiler has failed to complete its routine high-temperature cycle designed to prevent bacteria in your hot water tank, likely because the water is not getting hot enough.. It appears on 1 Navien model in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Legionella temperature: Legionella temperature not achieved within 48 hours
Typical repair cost £120-250 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like 127: 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.

Navien models that show the 127 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Navien 127 fault code information on this page is sourced and cross-checked against the official Navien service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026