Low
S.99 on Glow-worm Ultimate3 System

Your boiler is currently topping up its own water pressure automatically, which is a normal process and does not require you to do anything.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

Automatic filling active

From this model's manual
Verified against the Glow Worm Ultimate3 System installation & service manual, page 43.
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

Wait 15-30 minutes for the automatic filling process to completeObserve the boiler display to see if the code clears once the pressure is reachedIf the code persists for more than an hour, check for visible water leaks around the boiler or radiators

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