BoilerFaultCodesYour boiler has detected that there is not enough water in the heating system to operate safely, causing it to shut down.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Low system water pressure
What causes this fault?
This fault occurs when the internal pressure sensor detects that the system water has dropped below a safe operating level. The most common reasons are a slow leak from a radiator valve or pipework, or recent maintenance where air was bled from the radiators without topping the water back up.
This code is frequently seen in autumn when homeowners turn their heating back on for the first time and find that pressure has naturally seeped out over the summer months.
DIY fix possible
Locate the filling loop (usually a silver flexible hose) underneath or near the boiler.Slowly open the small valves on the filling loop until you hear water moving.Watch the pressure gauge and close the valves once the needle reaches between 1 and 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 37 — 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.