Central Heating Pump Guide: Everything You Need to Know

The central heating pump — also called a circulating pump or circulator — is the heart of your heating system. It pushes hot water from your boiler through the radiators and back again. When it fails, your heating stops working. In this guide, we'll explain how heating pumps work, how to spot problems, and how to choose the right replacement.

The Grundfos Alpha2L — one of the UK's most popular A-rated circulating pumps

How Does a Central Heating Pump Work?

A central heating circulating pump sits on the pipework near your boiler (usually on the flow pipe). It contains an impeller — a small rotating disc — that spins to push water through the system. Modern pumps are electrically powered, typically using between 5 and 60 watts depending on the model and speed setting.

The pump creates the pressure difference needed to move water through potentially hundreds of metres of pipework, multiple radiators, and various fittings. Without it, hot water would simply sit near the boiler with almost no circulation.

Signs Your Heating Pump Needs Replacing

Heating pumps typically last 10-15 years, but problems can develop sooner. Watch for these warning signs:

• No heating or hot water: If your boiler fires but radiators stay cold, the pump may have failed.
• Strange noises: Humming, buzzing, grinding, or clicking from the pump area often indicates worn bearings or a seized impeller.
• Leaking: Water dripping from the pump body or connections means seals have failed.
• Radiators heating unevenly: If radiators closest to the boiler get hot but distant ones stay lukewarm, the pump may be struggling.
• Pump is hot but not running: A pump that's hot to the touch but silent has likely seized internally.
• High energy bills: Older pumps running on high speed continuously waste significant electricity compared to modern variable-speed models.

Types of Central Heating Pumps

Fixed-Speed Pumps

Traditional pumps with 2-3 speed settings. You manually set the speed and the pump runs at that rate constantly. Cheaper to buy but less efficient over time. Common in older installations.

Variable-Speed (A-Rated) Pumps

Modern energy-efficient pumps that automatically adjust their speed based on demand. When thermostatic radiator valves (TRVs) close, the pump slows down, saving electricity. These can reduce pump energy consumption by up to 80% compared to old fixed-speed models. Browse our central heating pump range for the latest models.

Grundfos UPM3 Auto — variable-speed pump that adjusts to your heating demand

Choosing the Right Replacement Pump

When replacing a heating pump, match these key specifications:

• Connection size: Most domestic pumps use 22mm compression fittings, but some older systems use 28mm or 1.5" BSP connections.
• Body length: Measure the distance between the two connection nuts. Standard is 130mm or 180mm. Getting this wrong means the pump won't physically fit.
• Head pressure: Measured in metres, this indicates how much resistance the pump can overcome. Most homes need 4-6 metres of head. Larger properties or systems with many radiators may need more.
• Flow rate: Measured in litres per minute or cubic metres per hour. Your installer can calculate the required flow rate based on the system's heat output.

Popular Pump Brands

At APM Plumbing & Electrical, we stock circulating pumps from the industry's most trusted names:

• Grundfos: The market leader, known for reliability and efficiency. The UPS and ALPHA ranges are fitted in millions of UK homes.
• DAB: Excellent quality Italian pumps at competitive prices. The Evosta range offers superb energy efficiency.
• Wilo: German-engineered pumps with a strong reputation in both domestic and commercial heating.

Installation Tips

While pump replacement is a straightforward job for a qualified plumber or heating engineer, here are some key points:

• Always isolate the pump electrically and close the isolation valves before removal.
• Have towels and a bowl ready — there will be some water spillage.
• Flush the system if the old pump failed due to sludge build-up. A magnetic filter (like a MagnaClean) is a worthwhile addition.
• Bleed the new pump after installation to remove trapped air.
• If fitting a variable-speed pump, it will usually self-adjust — no manual speed setting needed.

Save Money with a Modern Pump

Replacing an old 60-watt fixed-speed pump with a modern 5-25 watt variable-speed model can save £50-80 per year on electricity. The pump pays for itself within 1-2 years. It's one of the simplest and most cost-effective heating upgrades you can make.

Get the Right Pump at APM

Not sure which pump you need? Bring your old one into our trade counter at 24 Western Avenue, Acton, London W3 7TZ and we'll match it up. Or call us on 020 8702 8080 — our team can advise on the right pump for your system. Shop our full range online at apmi.uk with next-day London delivery available.