High
E24 on Keston C36

Your boiler has shut down because it keeps losing water pressure and likely has a leak somewhere in the heating system or the unit itself.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

Water pressure losses - You have topped up the water pressure more than 4 times in 24 hours. You may have a leak on the system..

From this model's manual
Verified against the Keston C36 installation & service manual, page 32.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This fault occurs because the boiler has detected a significant and repetitive drop in water pressure, forcing it to shut down to prevent internal damage. It is usually caused by a physical leak within your radiators, pipework, or the boiler's internal components, such as a failing pressure relief valve. If the system cannot maintain a steady pressure four times within a single day, the software triggers this safety lock to alert you to the underlying leak.

This fault is frequently seen in autumn when the heating is turned back on after summer, as the change in temperature and pressure can cause weakened seals or joints to start leaking.

Engineer required

This is a high 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 →

Avoid the next call-out bill

A cover plan would handle faults like E24: 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

Related guides you might find useful