Boiler Pump Not Working: Causes And How To Fix It

Last Updated on February 18, 2025

As a homeowner or landlord in the UK, a malfunctioning boiler pump can quickly become a frustrating issue, especially during colder months when heating is essential. A faulty pump can disrupt the circulation of hot water throughout your heating system, leading to inadequate heating and increased energy bills. 

If you’ve noticed your boiler pump isn’t working, this article will provide insights into the potential causes and how you can fix it.

What Is a Boiler Pump and Why Is It Important?

A boiler pump, often referred to as a circulating pump, is a key component in your central heating system. Its job is to circulate hot water from the boiler through your radiators, taps, and underfloor heating. 

When the circulating pump malfunctions, hot water cannot flow properly, resulting in cold radiators, low water pressure, and a heating system that simply doesn’t work efficiently.

Common Causes of a Boiler Pump Not Working

There are several reasons why your boiler pump may stop functioning. Understanding these causes can help you pinpoint the issue and decide whether to attempt a repair or call in a professional.

1. Electrical Faults

The most common reason a boiler pump stops working is an electrical fault. If there is an issue with the power supply, the pump may not receive the necessary voltage to operate. This could be caused by a tripped fuse, a blown circuit breaker, or issues with the wiring.

How to fix it:

Check the Electrical Supply

If you suspect an electrical fault, check your boiler’s fuse box for tripped circuits or blown fuses. If everything appears in order, you may need to call a qualified heating engineer to inspect the wiring.

2. Airlock in the Pump

Airlocks in a boiler occur when air gets trapped in the system, preventing the pump from circulating water properly. Air can enter the system when you have recently had your system drained or if the pump hasn’t been used for an extended period.

How to fix it:

Bleed the System to Remove Airlocks

If air is trapped in the system, bleeding the radiators can help release the airlock. Turn off the heating, locate the bleed valve on the radiator, and release the trapped air. This can restore the flow of water to the system.

3. Pump Seized or Blocked

A pump can seize up due to debris or sludge buildup within the system. This can cause the pump to work harder, eventually leading to its failure. Regular maintenance and flushing the system can help prevent this issue.

How to fix it:

Clean or Replace the Pump

If the pump is blocked or has seized, you may need to have it cleaned or replaced. A professional heating engineer can flush out any sludge or debris from the system and check the pump for damage.

4. Faulty Pump Motor

The motor of the pump is responsible for its movement, and if it fails, the pump won’t work. A faulty motor can be due to age, wear and tear, or an internal electrical fault.

How to fix it:

Replace the Pump Motor

A faulty pump motor may require a complete replacement. If the motor has worn out, it’s best to contact a professional technician to replace the motor or the entire pump, depending on the extent of the damage.

5. Low Water Pressure

Low water pressure in the system can also affect the boiler pump’s performance. If the pressure is too low, the pump may struggle to circulate water, leading to overheating and potential damage to the pump.

How to fix it:

Top Up Water Pressure

Low water pressure is easy to fix by topping up the pressure using your boiler’s filling loop. Check your boiler manual for specific instructions on how to do this. If the pressure drops regularly, there may be a leak in your system that requires professional attention.

6. Worn Out Bearings

The bearings inside the pump help it rotate smoothly. Over time, these bearings can wear out, causing the pump to seize or operate inefficiently.

How to fix it:

Replace Worn Bearings

Worn bearings are often a sign of the need for a new pump. If the pump bearings are faulty, it’s usually best to replace the pump entirely to ensure optimal performance.

7. Thermostat Malfunctions

If the thermostat isn’t functioning correctly, it may not signal the pump to start when needed. This can lead to inconsistent heating, cold radiators, and system inefficiencies.

How to fix it:

Check or Replace the Thermostat

If the thermostat is malfunctioning, it may need to be recalibrated or replaced. A qualified technician can diagnose the issue and ensure your thermostat is operating correctly.

When to Call a Professional

While some of the fixes above can be done by a savvy DIYer, many issues with boiler pumps require professional expertise. If you are unsure of the cause or the fix seems complicated, it’s always a good idea to call a qualified heating engineer to avoid causing further damage to your system. 

Regular maintenance can also help prevent future problems and prolong the life of your boiler.

Need a New Boiler? Request a Free Quote Today!

If your boiler pump is not working and you think it might be time to replace your boiler, request a free boiler quote today. Answer a few simple questions about your heating needs and budget, and we’ll get back to you with a quote tailored to suit your specific requirements. 

Don’t wait – a reliable, energy-efficient boiler is just a click away!