Circulation Pumps: Selecting Grundfos and Wilo Replacements
If your radiators are cold at the top or your boiler is making a "kettling" noise, your central heating circulation pump may be failing. Understanding how to choose a compatible ErP-compliant pump like a Grundfos UPS3 or Wilo Yonos PICO is essential for a warm, efficient UK home.
The Heart of Your Heating System
In the UK, 90% of homes use a standard 130mm or 150mm port-to-port circulation pump. Modern "Smart" pumps save significant energy compared to old fixed-speed models:
- Energy Efficiency: Modern pumps use ECM technology to reduce electricity bills by up to 80%.
- Universal Fit: Most Grundfos and Wilo domestic pumps are designed to be direct swaps for older units.
- Self-Venting: High-end models automatically remove air, preventing "air locks" in your pipework.
Grundfos vs. Wilo: Which is Better?
Both brands dominate the UK market and meet strict European ErP regulations. Choosing between them usually comes down to what is already installed.
Where to Buy Circulation Pumps in the UK
Expect to pay between £100 and £180 for a high-quality domestic pump. We recommend buying from reputable merchants to ensure you receive a genuine unit with a full warranty.
| Retailer | Stock Status | Top Pick | Link |
|---|---|---|---|
| Screwfix | In Stock | Grundfos UPS3 15-50/65 | View at Screwfix |
| Toolstation | Available | Wilo Yonos PICO 25/1-6 | View at Toolstation |
| Amazon UK | Quick Shipping | Universal Replacement Pumps | Check Prices |
How to Replace a Circulation Pump
Replacing a pump is a common DIY task for those comfortable with basic plumbing. However, if your pump is integrated inside the boiler casing, you must hire a Gas Safe registered engineer.
Power & Water Off
Switch off the heating at the fused spur. Next, close the Gate Valves on either side of the pump by turning them clockwise. Warning: These valves often seize; if they don't move, you may need to drain the system.
The "Big Spanner" Job
Place a bucket underneath to catch spills. Use a large adjustable wrench or "water pump pliers" to loosen the large nuts (unions) connecting the pump to the pipework. Remove the old pump and old rubber washers.
Check the Flow Direction
Look for the arrow on the side of the new pump housing. It must point in the same direction as the old one (usually upwards or towards the boiler). Insert new rubber washers (always use new ones to prevent leaks) and tighten the nuts.
Plug and Play
Most modern Grundfos and Wilo pumps use a "Molex" style plug. Wire your existing cable into the provided plug (Live, Neutral, and Earth) and click it into the pump. Ensure the cable is secured and not touching hot pipes.
Bleeding the Air
Open the gate valves. Switch on the power. If the pump is noisy, it likely has air inside. Most modern pumps have an automatic de-airing function, but some older-style models require you to loosen the large silver screw on the front slightly until water drips out.
💡 Pump Troubleshooting Tips
- Stuck Pump: If the pump hums but doesn't spin after summer, it might be "stuck." Gently tapping the pump body or turning the internal shaft manually (if accessible) can often free it.
- Port-to-Port: Ensure you check the distance between the two threaded ends. Standard UK pumps are 130mm, but some older systems use 150mm or 180mm.
- Speed Settings: Always start a new pump on "Constant Pressure" or "Proportional Pressure" mode. High-speed settings are usually only needed for very large homes with many radiators.