Why Does My Boiler Keep Losing Pressure And How To Fix It

A pressure drop can leave you with lukewarm radiators, no hot water, or a completely non-functional boiler. The good news is that it’s often an easy fix if you know why your boiler pressure keeps dropping and how to fix it. Today, in this guide, we will explain them in detail.

If you need a professional diagnosis or fix your boiler pressure issues, our Gas Safe registered engineers at Citywide Plumbers are here to help. Whether it’s a minor leak, a faulty valve, or an expansion vessel problem, we have the expertise to get your heating system back on track.

Call us on 020 3892 8545 or email info@citywideplumbers.co.uk to schedule a professional boiler inspection!

Common Causes Of Boiler Losing Pressure

Ideally, the normal pressure for a modern boiler should be around 1.5 bars. If your boiler pressure keeps dropping, it could be due to one or more of the following issues under different circumstances:

1. If You Notice The Boiler Is Losing Pressure When Heating Is Off

If your boiler pressure keeps dropping even when the heating is off, it could indicate a slow pressure loss in the central heating system. This could be due to:

• A small leak in the system becomes more noticeable when the boiler cools down.
• A faulty expansion vessel failing to maintain pressure.
• A malfunctioning pressure relief valve (PRV) allowing pressure to escape.

2. If The Boiler Is Losing Pressure, But You Find No Leak

Sometimes, you may find your boiler has lost pressure, yet there are no visible signs of a leak in the system. This could be caused by:

• Air trapped in the circuit of pipes and radiators, leading to pressure drops when bleeding radiators.
• A failing expansion vessel unable to absorb pressure fluctuations.
• A slow leak inside the boiler that isn’t immediately visible.

If you can’t find a leak, but the pressure keeps dropping, it’s best to call a Gas Safe engineer for a thorough inspection.

3. If You Notice The Boiler Is Losing Pressure In Cold Weather

Many homeowners in West London notice their boiler is losing pressure in cold weather. The reasons include:

• Contraction of metal pipes due to temperature changes, leading to minor leaks.
• Frozen condensate pipes affecting boiler performance.
• Increased strain on the central heating system, highlighting pre-existing weaknesses.

To prevent pressure loss in winter, insulate external pipes and schedule regular boiler servicing.

4. If The Boiler Losses Pressure Overnight

If you wake up to find your boiler has lost pressure overnight, consider these factors:

• A gradual leak that only becomes noticeable after extended downtime.
• Pressure escaping through the pressure relief valve due to excessive build-up.
• A faulty filling loop allowing pressure to drop when the system is off.

5. If You Notice The Boiler Is Losing Pressure Every Day

The issue could be more severe if your boiler pressure keeps dropping daily. Possible causes include:

• A significant leak in the system, possibly under floorboards or within walls.
• A damaged expansion vessel unable to regulate pressure effectively.
• A malfunctioning pressure gauge giving inaccurate readings.

How To Fix A Boiler Losing Pressure

Now that you know about the reasons behind the pressure drop, follow these steps to restore your boiler’s pressure safely:

Step 1: Check The Pressure Gauge

Locate your boiler’s pressure gauge to determine if it’s below the recommended 1.5 bars. If it is, you’ll need to top up the pressure.

Step 2: Top Up The Pressure Using The Filling Loop

• First locate the filling loop, typically a silver or braided hose under the boiler.
• Then, open the valves slowly to allow cold water to enter the system, watch the pressure gauge until it reaches 1.5 bars, and close the valves securely.

Step 3: Bleed Radiators

If you hear gurgling noises or notice cold spots on your radiators, air may be trapped in your system. Bleeding the radiators with a radiator key can help balance pressure.

Step 4: Inspect For Leaks

Check around your boiler, radiators, and pipes for any signs of water. Even small drips can cause pressure loss over time.

Step 5: Call A Gas Safe Engineer

If your boiler pressure keeps dropping despite these steps, professional help is necessary. A Gas Safe engineer can diagnose deeper issues, such as a faulty expansion vessel, pressure relief valve, or hidden leaks.

Need Help? Call Citywide Plumbers

If your boiler pressure is persistently low, get expert help. Ignoring pressure loss can lead to inefficiency, breakdowns, and safety hazards. Citywide Plumbers provides expert boiler repairs and servicing across West London, ensuring your home stays warm and your heating system runs efficiently.

Why Choose Us?

• 15+ years of expertise – We have been providing plumbing and boiler services across West London, Islington and surrounding areas for over a decade, helping thousands of homeowners and businesses.
• Gas Safe registered engineers – Our team is fully qualified to work on all boilers, from modern combi boilers to conventional heating systems.
• Rapid response times—When a boiler loses pressure, action is urgent. That’s why we offer same-day callouts and emergency repairs across West London.
• Comprehensive services—We offer everything from leak detection and boiler repairs to installation and emergency plumbing services to keep your central heating system running efficiently.
• Advanced diagnostics and repairs – We use the latest tools and error code analysis to accurately diagnose faults and prevent recurring issues.
• Transparent pricing – No hidden fees! We provide upfront quotes and professional service you can trust.

Call us today on 020 3892 8545 or email info@citywideplumbers.co.uk to book a service in West London.

FAQs

Why does my boiler pressure keep dropping in the UK?

Leaks, a faulty expansion vessel, a malfunctioning pressure relief valve, recent radiator bleeding, or corrosion in the central heating system usually cause boiler pressure to drop.

Why does my boiler keep running out of pressure?

A boiler keeps running out of pressure due to leaks, a faulty expansion vessel, a malfunctioning pressure relief valve, or recently bled radiators releasing air, causing a drop in system pressure.

Can a boiler just lose pressure without a leak?

Yes, a boiler can lose pressure without a visible leak due to a faulty expansion vessel, trapped air in the system, recently bled radiators, or undetectable small leaks from system corrosion.

How to release pressure from a boiler in the UK?

To release pressure from a boiler in the UK, turn off the boiler, use a radiator key to bleed the radiators slowly, and let out excess air and water until the pressure stabilises. Always check the pressure gauge to ensure it’s within the recommended range.

Call a professional heating engineer for assistance if you’re unsure or the pressure remains too high.