BoilerFaultCodesYour boiler has stopped working because the water pressure in the system has dropped too low and needs topping up.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Primary system water pressure too low
What causes this fault?
This fault occurs when the pressure within your central heating system drops below a safe operating level, usually because water has escaped the circuit. The most common reasons for this are a leak in the radiator valves or pipework, or air being released from the system through recent bleeding of the radiators.
This fault is frequently seen in autumn when homeowners turn their heating back on for the first time after summer, revealing pressure drops that occurred during the warmer months.
DIY fix possible
Locate the filling loop (usually two braided silver hoses or blue levers) underneath the boiler.Open the valves slowly until you hear water entering the system.Watch the pressure gauge and close the valves tightly once the needle reaches 1.5 bar.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like E118 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
Affiliate links — we may earn a commission at no extra cost to you.