Why Is My Boiler Losing Pressure? How to Increase Boiler Pressure

If your boiler pressure keeps dropping or your heating isn’t working as efficiently as it should, you’re not alone. Many homeowners experience boiler pressure issues — and in most cases, it’s easy to fix.

In this guide from Plumbrite Services, your local boiler repair experts in the West Midlands, we’ll explain:

• Why your boiler might be losing pressure

• How to safely increase boiler pressure

• When it’s time to call a professional engineer

What Is Boiler Pressure?

Boiler pressure measures the balance of water and air within your central heating system. It’s displayed on your boiler’s pressure gauge, typically found on the front panel.

• ✅ Normal pressure: Between 1 and 2 bars (when cold)

• ⚠️ Low pressure: Below 1 bar – your heating may stop working properly

• 🚫 High pressure: Above 2.5 bars – can lead to leaks or safety issues

If your boiler pressure is too low, your heating system won’t be able to circulate hot water effectively, leaving you with cold radiators and poor heating performance.

Why Is My Boiler Losing Pressure?

At Plumbrite our Gas Safe engineers are often called out to fix pressure loss. Here are the most common reasons your boiler might be dropping pressure:

1. Leaks in the Heating System

Even the smallest leak from a pipe, valve, or radiator can cause your boiler pressure to fall. Check around your home for damp patches or small water stains near radiators or pipes.

2. Air Trapped in Radiators

If your radiators are warm at the bottom but cool at the top, air may be trapped inside — which can affect pressure. Bleeding the radiators can often fix this issue.

3. Faulty Pressure Relief Valve (PRV)

The PRV is designed to release excess water when pressure is too high. If it’s leaking or malfunctioning, you’ll see repeated drops in pressure.

4. Bleeding Radiators Recently

After bleeding your radiators, it’s normal for pressure to drop slightly. A quick top-up via the filling loop usually resolves this.

5. Expansion Vessel Problems

Your boiler’s expansion vessel helps maintain stable pressure. If the internal diaphragm fails, it can lead to ongoing pressure loss and may need to be repaired or replaced by a professional.

How to Increase Boiler Pressure (Step-by-Step)

If you’re comfortable topping up your boiler yourself, here’s how to do it safely:

⚠️ Safety note: If you’re unsure or your boiler keeps losing pressure, contact Plumbrite Services — we are always happy to help.

Step 1: Turn Off the Boiler

Switch off your boiler and allow it to cool before making any adjustments.

Step 2: Locate the Filling Loop

Most modern combi boilers have a silver braided hose beneath them — this is the filling loop.

Step 3: Open the Valves

Turn the valves slowly to let cold water from the mains into your heating system. Watch the pressure gauge rise.

Step 4: Close the Valves

When the gauge reaches between 1.2 and 1.5 bars, close both valves firmly.

Step 5: Turn the Boiler Back On

Restart your boiler and check that the pressure remains stable.

🚫 What Not to Do

• Don’t overfill your boiler — pressure above 2.5 bars can trigger leaks or damage.

• Don’t ignore a system that keeps losing pressure — it usually means there’s an underlying issue.

When to Call the Experts at Plumbrite Services West Midlands

If you’ve topped up your boiler and it still keeps losing pressure, it’s time to call a professional.

At Plumbrite Services, we’re proud to be trusted Gas Safe registered heating specialists. We can:

• Detect and repair leaks in your heating system

• Test and replace faulty valves or expansion vessels

• Perform full system diagnostics and pressure tests

• Get your heating back to full efficiency quickly and safely

If you’re in Kingswinford and the surrounding areas Paul is ready to help.

FAQs About Boiler Pressure

❓ Why does my boiler pressure keep dropping?

Most commonly, due to leaks, radiator bleeding, or a faulty pressure valve.

❓ Can I fix boiler pressure myself?

You can top it up, but any internal repairs should only be handled by a Gas Safe engineer.

❓ How often should I top up my boiler pressure?

Only once or twice a year. If you need to top up frequently, there’s likely an issue that needs inspection.

❓ Does low pressure affect heating performance?

Yes — low pressure stops water circulating properly, resulting in cold spots and poor heating.

Final Thoughts

A boiler losing pressure can be inconvenient, but it’s usually easy to diagnose and fix. Regular maintenance and pressure checks can prevent bigger issues later on.

If you’re based in the Black Country and your boiler pressure keeps dropping, don’t wait — contact Plumbrite Services.

Our friendly, Gas Safe registered engineers will quickly identify the cause, restore your system, and ensure your home stays warm and energy-efficient.